REPORT JARGON BUSTER
DAMP AND TIMBER SURVEY REPORT TERMINOLOGY
When instructing a surveyor to carry out a damp and timber survey on a property, whether it be in the case of a pre-purchase, house part exchange, re-mortgage or for rising damp, wood boring insects (woodworm) or dry rot, you will inevitably, after the survey has been carried out, receive a report from the valuation surveyor working on behalf of the mortgage loan company. This will detail the construction, condition of the house or flat, and any defects found. Whether it’s a building survey or a specialist damp and timber survey to satisfy the mortgage lenders, the report will, I’m sure, state the obvious, but will also use terms which you may find confusing. Phrases such as “timbers in contact with dampness may be at risk to fungal timber decay” or even terms such as woodworm, roof purlins, rendering & d p c mean nothing to some people. We have come across lots of clients who are in the process of selling / buying a new house or flat and have been confused by some terms used by the surveyor in his report and others who are wondering “what in the world does that mean?”!! This damp and timber report jargon buster web page has been designed to help you cut through the jargon. For honest and practical advice on all aspects of the control & diagnosis of dampness and fungal timber decay please feel free to contact Damp Aid by phone or email firstname.lastname@example.org .
Air Bricks / Sub-floor ventilation air vents & Sub floor timber inspections for dampness including checking for timber decay defects, which involves lifting floor boards to gain access the structural sub floor timbers.
Sub-Floor Inspection to timber suspended ground floors for timber defects and wood decay. Moisture prevention starts with effective sub-floor ventilation. Moisture and damp is the enemy of any property able to penetrate the fabric of any building. Inadequate sub floor ventilation is responsible for timber decay, woodworm, wood boring beetle infestation, dry- wet rot degradation, and a whole host of costly damp & timber treatment works.
Sub-floor ventilation inspections for ground floor suspended timber flooring. A minimum ventilation void of 150mm should be provided to the underfloor voids below floor joists or 75mm below any wall plate. On shrinkable soil where heave could take place, an allowance for movement should be added to the underfloor ventilation requirement to determine the minimum dimension of the underfloor void. The allowance for movement relates to the shrinkage potential of the soil as follows: • high potential – 150mm • medium potential – 100mm • low potential – 50mm. Where sub floor ventilation is inadequate the walls should be ventilated by openings providing not less than 1500mm² per meter run of external wall or 500mm² per m² of floor area, whichever gives the greater opening area. Ventilators should be spaced at not more than 2m centers and within 450mm of each end of any wall. Air bricks should be duct-ed through cavities and be unobstructed. Every part of the void under a timber suspended ground floor should be thoroughly ventilated through openings on at least two opposite sides.
Where this is not possible, effective cross ventilation from opposite sides should be provided by a combination of openings and air ducts. These vents cost around £70-£80 and can be installed into under floor voids by any competent builder who has had experience with sub floor ventilation building regulations.. Provision should be made for sub floor ventilation through partitions and sleeper walls. If necessary, pipe ducts should be incorporated in adjoining solid floors, separating walls or other obstructions. Ventilation should not be obtained through a garage. British Standard BS 5250:2002 Timber 184.108.40.206 Sub floor cross ventilation should be provided by openings not less than either 1500mm²/m run of external wall or 500mm²/m² of floor area whichever gives the greater opening area.
Architects design new buildings and the spaces in and around them and help restore, conserve and adapt old building structures. They usually get involved at the start of a construction project, developing designs that interpret a client’s vision. Their work includes – preparing and presenting building design proposals; producing detailed drawings and damp and timber specifications; liaising regularly with damp-proofing & timber treatment surveyors and other built environment professionals; visiting construction sites to assess progress and inspecting the quality of work, ensuring it follows the agreed architectural design.
The British Standards Institute administers ‘Kitemark’ licences relating to a very wide range of goods, materials and systems used in all areas of the construction industry. For example, BS 6576 sets out a code of practice for installing chemical damp proof courses. The BSI also administers the ISO 9000 series of quality management standards. For more information contact BSI, 389 Chiswick High Road, London W4 4AL
This is a far more detailed survey formerly known as a ‘Structural Survey’. The report will give a detailed account of any property defects and the best course of action to rectify the problems. It will also give advice on matters that may become a future issue. This can cost anything from £500 – £4,000 depending on the value of the property.Whilst surveyors will be able to identify and determine the cause of any problems, further specialist advice is usually recommended to obtain an estimate for remedial damp timber repairs or to obtain access to areas that could not be seen during the surveyor’s inspection e.g. at roof level. In the event of a survey highlighting areas of concern, we would strongly recommend you obtain the opinion of a specialist before deciding on which course of action to take. Some of the more common problems are: Structural issues, problems relating to the roof, potential damp and timber defects
Building Conservation Officer
Building conservation officers work to promote and preserve historically important buildings by offering advice on how to maintain them in an architecturally accurate and sympathetic way. They may work with many different types of buildings, including houses, churches, windmills, lighthouses and factories, ensuring that they survive for future generations to enjoy. As well as providing valuable evidence of the way people lived and worked in the past, such buildings also help to preserve the character of our cities, towns and villages for the future.
Building Control Surveyor
Building control surveyors make sure that building regulations and other legislation are followed when houses, offices and other buildings are designed and constructed. Before construction gets underway, building control surveyors check applicants plans, drawings and specifications to make sure they meet the regulations. Surveyors can reject plans that fail to meed building regulations or issue certificates for work to commence. Once work begins, building control surveyors visit sites at various phases of construction, checking that work is carried out properly and to the right standards. A building control surveyor issues completion certificates. They may also authorise entertainment licenses, conduct public venue safety inspection, respond to emergencies to assess building safety and approve building demolition. A building control surveyor will also check that property alterations such as extensions meet regulations.
Building surveyors advise property and construction clients on areas ranging from the design and development of new buildings to the conservations and restoration of historic buildings. Specific duties can include – advising on technical, financial, environmental, building regulations, restoration and property legislation matters. Completing property and land surveys and valuations, writing up technical reports and recommendations, preparing plans, contracts, budgets and other documentation, submitting planning applications and grant requests, overseeing building work and managing projects, giving advice surrounding legal and potentially contentious issues such as insurance claims and liability costs.
British Wood Preserving & Damp-proofing Association. See PCA below for more details.
Cavity air gap membranes /cavity drainage membranes
This membrane is a high density polyethylene extruded membrane which is fixed mechanically to the walls, ceilings and floors but with an air gap for the movement of water vapour. The membrane has studs varying from 3mm to 20mm which retain an air gap between the wall and the membrane. Any water egress behind the membrane will discharge down the wall and into a secret perimeter drainage system. This drainage system is laid at a slight fall and water is then collected in a sump unit which incorporates a pump to then discharge the water to the nearest drain. The wall membrane is mechanically fixed through the studs using a waterproof fixing, complete with rubber waterproof grommet. An independent stud partition is then erected on the inside of the membrane which then accommodates wiring, pipe work, plasterboard and finishes in the usual manner. Metal studding is particularly suitable for basement applications.Floor membranes similarly have a small air gap and the polyethylene membrane is extremely crush resistant thereby allowing a floor screed to be applied as a useable finish. Alternatively a floating floor comprising polystyrene insulation and tongue and grooved chipboard or Weyroc can be used.Cavity air gap waterproofing systems are relatively fast to install and commonly have a 10 to 30 year guarantee. It is normal to have the sump and pump unit maintained annually to ensure no build up of grit or debris. With the current and future increase in flood risks some consideration should be given to an independent power pack that provides a battery back up supply should a power cut occur. Similarly high level water alarms can be fitted to advise if the unit is failing or water is rising unexpectedly fast.It should be expected that any membrane waterproofing system would carry a BBA (British Board of Agreement) Certificate for the membrane material.
A main, external, wall built of two leaves of brick, stone or a type of block, and a space in between. Normally the inner leaf is load bearing and the function of the outer leaf is to protect the inner leaf from the weather, the two leaves are linked by ties, normally of metal. A cavity wall is usually more resistant to damp penetration than a solid wall, and has greater thermal insulation.Cavity walls began to be used in the late Victorian period. Again, these usually incorporate a slate damp proof course DPC but this can be bridged inside; surplus and decaying mortar from the wall may drop to the bottom of the cavity. If there is a sufficient quantity, this debris may build up to a point above the DPC, bridging the inner and outer skins. The only solution is to cut out bricks at intervals, below the DPC, and rake out the debris. This can also occur above window and door openings. This problem has appeared in houses built as late as the 1930s, particularly where lime has been incorporated in the mortar.
Cavity Wall Tie Failure
This is the result of the rusting of wall ties in older cavity walls. The zinc coating of galvanized ties degrades naturally and for many years was insufficiently applied to provide really long-term protection. The problem is also accelerated by black ash mortar (commonly used for early cavity walls), chloride salts and carbonation. In 1981 the British Standard for such coatings was raised to incorporate a thicker coating. The problem is normally identified by horizontal cracks in every 4th or 6th mortar joint due to the expansion of the rusting ties in the outer skin. Occasionally, the ties degrade within the cavity and the skins are no longer linked. Once discovered, the only solution is to replace all wall ties in the external walls.
Cavity Wall Insulation Technicians
Cavity wall insulation technicians, also know as insulation installers, fit insulation materials between the inner and outer walls of new and existing buildings, in order to conserve energy. They may also lay loft insulation, fit draught- proofing and install sound proofing materials. Usually working alongside another trades person, their duties involve – surveying properties first to determine the best methods and materials to use, producing a written report for customers, marking out ventilation, wiring and pipework ducts, calculating the volume of space to be filled and the amounts of material required, drilling holes in the building walls, pumping insulating material in the wall cavity.
Cemetitious Multi-Coat Render (tanking)
Another popular method of basement waterproofing is a cemetitious render whereby multiple coats of render, with a waterproofing agent in a dense sand/cement mix, is applied to the walls and floor. The technique endeavors to create a fully lapped joint of each wall and floor layer of render, thereby creating a fully integrated waterproof lining.It is vital that the basement surface is fully prepared to form an excellent key for bonding purposes with no loose material or contamination. Whilst this method of waterproofing has proved successful in the past, there is no mechanism for the release of any hydrostatic build up of water pressure and thus a sealed membrane system is often a preferred method. Additionally the cemetitious render must not be punctured in any way thus fixing of sockets, pipes and light fittings can be an issue and an inner stud partition leaf is often used.
Chemical injection Damp proof course
Chemical damp-proof courses are inserted into walls to control the vertical passage of moisture from the ground, and are almost all installed in properties where no damp-proof course exists or it has broken down with age.
The most common form of unwanted dampness in houses and flats is water from the air that forms as condensation.The air in buildings can have a high level of relative humidity due to the activity of the occupants (e.g. cooking, drying clothes, breathing etc.). When this water laden air comes into contact with cold surfaces such as windows and cold walls it can condense, causing water to be deposited. The point at which the water held in the air changes from vapour to liquid is known as the dew point.
Condensation is often associated with poor heating and ventilation in buildings, but this simple view can be misleading. Condensation is chiefly a winter problem, as the external air temperature is low and external walls and windows are cold.
The usual sequence of events is as follows:
Cold air enters the building
The air is warmed for the comfort of the occupants.
The warm air takes up moisture.
The warm, moist air comes into contact with cold surfaces, walls, windows, etc. and is cooled below its Dew Point.
Condensation occurs as the excess moisture is released.Walls in kitchens and bathrooms (where atmospheric moisture levels are usually highest), solid external walls, UN-insulated solid floors and cold bridges such as concrete lintels set in cavity walls are commonly the areas in which condensation takes place.Intermittent heating and cooling of the property can aggravate condensation problems, since it allows warm damp air to cool, reducing its capacity to hold water. Dew points are reduced allowing condensation to occur. When the air is reheated water is taken back into the air only to be deposited again when the air temperature drops again.
Containment barriers provided to contain dry rot mycelium within an area of wall by introducing a masonry biocide through the full thickness of a wall, combined with a surface application over the area contained by the perimeter. This is used to protect masonry adjacent to a dry rot outbreak. (see also Toxic Box below).
Damp and Timber Specialist Survey & Report
A timber and damp specialist survey report will identify any areas of rising or penetrating damp timber defects. Cost of an damp & timber inspection and report is usually fairly minor. Fees for damp surveys are usually refundable if the company is subsequently instructed to carry out the required damp and timber treatments.
Damp Treatment Costs.
Cost of damp treatment can vary greatly depending on a number of factors. The extent of damage caused by rising dampness and the labour involved to remove damaged plaster and installing a chemical damp-proof course will also affect the cost of damp treatment. Different types of damp-proofing treatment used can also have an effect on the cost
Damp-proof course (DPC)
Often abbreviated as DPC. A layer of impermeable material built into a wall to prevent damp rising within it. Older damp proof courses are often of slates; more recently felt impregnated with bitumen; modern construction uses heavy duty polythene. A chemical damp proof course can be injected into an old wall, forming an impermeable layer within the masonry, although its efficiency varies with the type of construction. A vertical damp proof course is required to keep a room below ground level dry(known as tanking), or where a horizontal damp-proof course may be bridged. Damp proof courses are also installed in other parts of a structure.
Damp-proof courses (DPC) and their history
Georgian Houses (1714 – 1837)
Georgian properties did not have a physical damp-proof course. The Georgians were very conscious of ensuring good ventilation as well as keeping the amount of moisture they created to a minimum.
Victorian Houses (1837 – 1901)
Solid brick walls like those you find in many early Victorian properties can cause condensation issues as they are large cold surfaces. If the original render fails, they can also allow weather like driving rain to penetrate. In Victorian properties, timbers were used in construction that are at risk of becoming rotten due to damp.
Late Victorian Houses (1870 – 1901)
Cavity walls were first used in the late Victorian period. This type of wall consists of two leaves – the outer leaf which acts as a protective skin against the weather and the inner leaf which provides a dry surface to decorate. The air in between the two leaves prevents damp from passing from the outer layer to the inner, acting as a barrier to moisture.
DPCs became compulsory in London in 1875. A layer of slate was also employed as a DPC in Late Victorian properties. However, over the years decaying parts of the wall can fall into the cavity and potentially rise above the level of the DPC, bridging the air gap.
Air bricks were also introduced in the late Victorian period and into the Edwardian period. The bricks, originally made from clay, were installed in walls and under floors allowing air to circulate and provide improved sub-floor ventilation to timbers at risk of timber decay.
Edwardian Houses 1901 – 1910 (1915)
Most Edwardian houses did have a form of damp-proof course to deal with rising damp. Bitumen, slate and occasionally hessian damp-proof courses were used along with a band of engineering bricks to act as a physical damp-proof barrier. Damp problems usually occur if the DPC has failed, becoming cracked or damaged over time
Damp-proof membrane (DPM)
A sheet DPC underneath a solid floor to keep the surface dry.
A concentrated silane/siloxane ‘cream’ which is slowly diffused into the masonry. When it reacts with the silica in the masonry it forms a water repellent barrier.
The true Dry Rot fungus (Latin name Serpula lacrymans) is the more serious of the wood destroying fungi. It causes extensive damage to structural timbers if not treated in time. It will spread undetected behind wall plaster,sub floor voids and even through thick walls in search of timber to attack. Timber affected by dry rot is brown, dry and brittle with cube shaped (cuboidal) fractures and can be crumbled by hand. The fruiting body (or fungus/mushroom growth) gives off millions of spores which resembles red dust and is often mistaken for brick dust.
Electrical Osmotic damp-proof course system (Electro-Osmosis).
This a chemical free environmentally friendly damp proofing option for controlling rising dampness involves inserting a continuous titanium band in the mortar joints and the insertion of electrodes. This electro-osmotic damp-proofing system method relies upon an electrical supply to prevent further dampness from rising up the wall, but the band and electrodes are easily damaged. It is worth bearing in mind, that during the selling of your house or the buying of a property which has this system installed, it should be switched off before the home buyer / valuation surveyor tests the walls for dampness, as high moisture content meter readings will be recorded during the damp survey giving a false impression that possible rising damp is present, thus incurring potential costs for unnecessary remedial damp-proofing work. This damp-proof course system was introduced to Britain by W J Holmes of Rentokil and was installed in many houses by rentokil in the UK between 1962 and 1974 before being superseded by the ever popular injected damp proof course method.
Exchange of Contracts
Once the contract has been signed by both parties and you have transferred the deposit to your solicitor (normally 10% of the purchase price), your solicitor should be getting close to being ready to exchange contracts. You will normally need to have agreed on a completion date with the seller prior to exchange of contracts. This is done either directly or more usually via the solicitors or estate agents. At exchange of contracts the purchase becomes legally binding. If either party were to pull out of the transaction at this time, there are likely to be heavy financial implications for the person that withdraws from the sale.
External ground lowering
Carried out where external ground level is bridging the damp proof course
Freezteq – Frozen damp-proof course system. (BBA Cert. 92/2849)
Involves drilling holes at the base of walls to within 25mm of the wall thickness and then inserting frozen ice sticks of damp-proofing fluid into the holes and then after they have melted and diffused into the brickwork repeating the process of inserting the frozen ice sticks of damp-proofing fluid a further three times with the entire operation to be completed within a 24 hour time period.
The sticks come delivered unfrozen in plastic sachets and the damp-proofing fluid is a blue liquid and once frozen they look like ice-pops.
Advantages- no injection pump is required as the damp-proofing fluid diffuses into the wall slowly as the ice-stick melts.
Disadvantages-Time consuming. Fluid needs to be frozen, then sticks inserted four times over to achieve full damp-proof course.
Fungal Decay in Building Timbers
Dry rot and wet rot can affect buildings of all ages and if decay is discovered it should be identified and remedial action taken without delay.
Fungal decay occurs in timber which becomes wet for some time and is the result of the attack by one of a number of wood-destroying fungi. The most well known are Serpula lacrymans – the true dry rot fungus -, Coniophora puteana the Cellar fungus and Poria vaillantii the Pore or Mine fungus. Many other fungi also occur and some have recently been particularly linked with decay in door and window frames.
Dry rot is only caused by Serpula lacrymans and is the most serious form of fungal decay in a building. It can spread onto and destroy much of the timber. Wet rot occurs more frequently, but is less serious; decay is typically confined to the area where timber has become and remains wet.
Fungal decay always arises because the wood has become wet, usually timbers will be in excess of 20 per cent moisture content. Finding the source of dampness and eliminating the ingress of moisture and promoting drying is always necessary.
Outbreaks of dry rot and wet rot start in similar ways. The mature fruiting bodies of wood-destroying fungi that develop during an attack produce millions of microscopic spores and these are widely dispersed by air currents. If they fall on untreated damp wood they will germinate by pushing out a hollow tube called a hypha which grows and branches to form a mass of hyphal threads called mycelium. Mycelium develops inside the timber and breaks down the wood for food. The timber may darken in colour and develop a characteristic cracked appearance. Some wet rots may result in bleaching of the wood; these are more common in doors and window frames. Eventually, the wood loses its strength and in some situations may become dangerously unsafe.
The main differences between dry rot and wet rot are the degree of development of mycelium on the wood surface and the ability of the fungus to spread into other timbers via adjacent masonry. It is important that the two types of decay be distinguished by a dry rot surveyor since they require different treatment.
Historic Flooring Table
TUDOR & JACOBEAN (1485-1625)
Houses usually had flagstone, brick or tiled floors on the ground levels with wooden floors on the upper storeys.
WOOD TYPE: Usually oak, occasionally elm
FIXING TYPE: Face nails
STYLE: There was an abundance of wood available in the 15th and 16th centuries, so craftsmen could be extremely choosy about the quality of timbers laid. It was not uncommon for boards to be anything up to 60cm wide. Planks were laid in varying widths.
Stone flags covered principal and service rooms on ground floors, while wooden floors predominated on upper floors. In the East Midlands at this time upper floors were made of lime putty on laths.
WOOD TYPE: Oak continued to be the predominant choice
FIXING TYPE: Face nails
STYLE: Marquetry and parquetry became fashionable in 17th century grand homes. Patterns were sometimes painted onto plank floors to achieve a similar look. In less important rooms, boards were left untreated and scrubbed regularly with sand. Planks were often more than 30cm wide.
Stone floors over joists were typically found in entrance halls, with wooden floors in other rooms. Oriental, Turkish and floral carpets were introduced throughout houses, covering main thoroughfares and large communal areas.
WOOD TYPE: Oak was still used, with elm becoming much more commonplace. By the mid-1700s, Baltic fir and pine were being used.
FIXING TYPE: Face nails with metal dowels and plates. Tongue and groove fixing was introduced.
STYLE: In the late 18th century boards were stained and polished around the edges to frame carpets. Boards became much narrower, usually 15 to 20cm wide. Fixed-width boarded floors were also introduced. By the latter part of the Georgian period, polished oak planking was reserved for main staircases in grand houses, with unvarnished fir and pine floorboards used for most floors in simple houses. The trend for marquetry and parquetry continued throughout the period.
Wooden floors were the standard flooring throughout houses.
WOOD TYPE: Oak was the preserve of principal rooms in grand houses. Baltic fir and pine used elsewhere.
FIXING TYPE: Face nails together with metal dowels and plates
STYLE: Boards were stained, polished, painted or varnished. As England’s vast forests thinned out, wood became less plentiful and the width of the boards narrowed to between 18 and 23cm. Marquetry, parquetry and better timbers were limited to the richest rooms in the finest houses.
VICTORIAN / ARTS & CRAFTS / ART NOUVEAU
(1837-1901) (1860-1925) (1888-1905)
Plain pine floors were used throughout most Victorian houses. During the Arts & Crafts period wood and stone were the only acceptable forms of flooring. Tiles became the predominant material in entrance halls during the Art Nouveau period.
WOOD TYPE: Pine used extensively throughout the period but the Arts & Crafts movement revived the passion for oak and gave rise to an interest in exotic hardwoods and maple. Well-chosen pine and fir planks were considered acceptable.
FIXING TYPE: Tongue and groove fixing or face nailing were the norm.
STYLE: Pine floors were usually covered with rugs and the surrounds were stained and polished with beeswax and turpentine to create the effect of a better timber. Some borders were stencilled as an inexpensive alternative to parquetry. During the 1860s, floors painted in Indian reds and deep blue’s became fashionable. In Arts & Crafts buildings, the preferred wood, oak, was simply polished to enhance its natural beauty. The finest floors were cut from the full-width of tree trunks. The movement also created the trend for floors and wall panelling to be stained in similar dark tones. Staining, however, was reserved for inferior woods. In Art Nouveau interiors, carpets and rugs were considered the main decorative features so wood and parquet borders were polished to provide a simple, complementary backdrop.
Tongue and groove boards became the most popular form of flooring in homes. Entrance halls were normally tiled.
WOOD TYPE: Pine boards were widely used, oak and teak were reserved for grand houses and villas.
FIXING TYPE: Tongue and groove fixing or face nailing were the norm.
STYLE: polished oak and teak were found in grander houses. Pine was varnish-stained around the edges to frame a carpet and rug. Wall-to-wall carpets were introduced, initially
into the principal reception rooms. Parquet was still popular and was constructed from blocks 2.5cm thick, laid on a cement base covered in bitumen. Parquet in suburban houses was usually constructed from panels of thinner blocks fixed to a cloth backing. The most common parquet style was herringbone, stained or polished and found in kitchens, hallways and living rooms.
1920s & 1930s (ART DECO, MODERNISM, etc)
Linoleum became a favourite material and wall-to-wall carpets appeared only in the most exclusive homes.
WOOD TYPE: Lighter woods were preferred
FIXING TYPE: Tongue and groove fixing or face nailing were the norm.
STYLE: Parquetry became a standard treatment so elaborate patterns became more widespread.
A Homebuyer Report covers the same issues as a Building Survey, but in less detail. The report should include a brief description of any defects and where necessary will indicate what should be done to rectify any problems. A Homebuyer Report includes a valuation of the property for the client’s use whereas the Building Survey does not. This report should cost between £300 – £1,000 and is usually based on the value of the property
Hygroscopic means “the ability to absorb moisture from the surrounding environment”. The salts (Chlorides and nitrates) which originate in the soil, are transported with damp as it rises through masonry. Hygroscopic salts can cause walls to remain damp even if there is no source of water ingress.
Institute of Wood Science – The purpose of the Institute of Wood Science is to advance and encourage the scientific, technical, practical and general knowledge of timber and wood based materials.
Independent / Freelance Surveyors / Consultants
A ‘PCA registered Independent damp Surveyor’ is an individual who offers a specialist damp and timber surveying service and has no commercial link or interest with any organisation or individual that derives profit or gain from the undertaking of damp proofing and timber treatment preservation work in buildings.
A ‘PCA registered Freelance damp-proofing & timber treatment Surveyor’ is an individual who offers a specialist damp and timber surveying service but has a declared commercial link with one or more organisations or individuals that derive profit or gain from the undertaking of building preservation work.
A ‘P. C.A . registered Independent damp and timber Consultant’ is an individual who offers a specialist building preservation consultancy including surveying and site investigation services for rising damp, timber decay, & wood boring beetles ( WOODWORM ) and will not provide estimates for rectification or undertake any damp proof course and timber repair works. Consultants are deemed to have the ability to act as an independent witness in litigation cases and are able to produce CPR 35 compliant damp and timber surveys & reports in accordance with civil procedures.
Penetrating Damp is caused by moisture penetrating through the roof or walls. Causes include: defective pointing / flashing, faulty rainwater goods, defective roof coverings, plumbing leaks, defects around window joinery and doors, and many more. Such defects generally cause localized problems and readily become evident in the form of damp patches appearing.
PCA (formerly BWPDA)
Property Care Association – The PCA is the premier trade body representing specialists in structural waterproofing, damp proofing, wood preservation, structural maintenance & flooding
a large horizontal timber, part of the roof structure, supporting the rafters, and normally supported by load bearing walls.
Quantity surveyors are essentially construction accountants, managing the costs and contractual side of building and civil engineering projects. This means they must follow one of the degree level routes that the Royal Institution of Chartered Surveyors (RICS), Chartered Institution of Civil Engineering Surveyors (ICES) or the Chartered Institute of Building (CIOB) approves.
A sloping timber, part of the roof void structure, supporting the tile or slate battens and probably resting on purlins.
Re-pointing is the process of taking out and replacing the mortar (‘pointing’) from the face of a masonry joint. Done properly, this helps exclude the weather and retard deterioration of the wall. Regrettably, re-pointing is commonly undertaken unnecessarily or unsatisfactorily. Unnecessary re-pointing, however carefully done, risks damage to the edges of bricks or stones, as well as the loss of valuable clues to a building’s construction and history. Unsatisfactory re-pointing can not only be visually disturbing, but harmful to the actual fabric it is intended to protect.
Rising Damp is simply, water from the ground that enters a structure by capillary action. Water that enters or affects a building through any other route can move about in various ways but is not rising damp. Only rising damp can be cured by the installation of a chemical damp proof course.Rising damp is a commonly encountered problem in some types of building, however it is often misdiagnosed. It is important that the investigations into dampness are undertaken by a trained and competent surveyor who can recognise and understand the problem. We would always recommend that the surveyor who undertakes investigations has been awarded the CSRT qualification.
Decayed skirting boards, crumbling or salt stained plaster, discoloration and staining, decayed timber floors, peeling paint and wallpaper are all common when walls are affected by rising damp. These defects are not always evident but when they are, a specialist damp and timber inspection is always recommended.
Most types of masonry used in the walls of buildings will allow some water movement by capillary action; however, this is usually controlled by a physical barrier or damp proof course. If this physical barrier is absent, has broken down or is damaged then it is often possible to install a remedial damp proof course (DPC) to control water rising from the ground.
Water rising from the ground often introduces contaminating salts into the walls and plaster coats. This contamination will often result in a need for the plaster to be removed and replaced using specially formulated salt resistant plasters.
Members of the PCA have the skills and experience needed to diagnose report on and repair buildings affected by rising damp.
Rural surveyors manage the interest of landowners and tenants of rural properties. The may manage one or several estates and advise on – the law, rural estate management of staff, stock and land; forestry and woodland management’ conservation, building maintenance and the extraction of minerals from land; agricultural matters; developing the non-agricultural use of rural land.
Electrical moisture meters will respond to very small quantities of free moisture and certain contaminant salts. In building materials the latter are usually hygroscopic, that is they have the ability to absorb moisture from the atmosphere. The more humid the atmosphere the greater the absorption of atmospheric moisture, and also the greater the concentration of salts the greater the absorption of moisture. Where such contamination exists alone (that is without the presence of free moisture) high electrical moisture meter readings will be obtained even though the surface may appear visually dry. However, where contamination is high, and should it get into decorative finishes there are occasions when a wall can look very damp solely as a result of moisture absorption from the air. Such dampness is regarded as ‘salt damp’.
Silane diffusion (dpc cream) – (e.g. Peter Cox Drywall Diffusion dpc BBA 02/3976 or Safeguard Dryzone BBA 97/3363)
This involves drilling 10mm holes into the mortar joint and injecting a damp-proofing cream into the holes with a caulking gun or hand pump. The cream slowly diffuses, releasing a vapour which reacts within the masonry to form a water repellent resin, thus forming a barrier against rising damp.
Siliconate transfusion – (e.g. Wykamol Siliconate K dpc – BBA 02/3961)
Holes are drilled into the wall and then a series of units and tubes are inserted into the holes. The transfusion units are then filled with the siliconate fluid (enough to saturate the brickwork) which is then gravity fed from the units into the brickwork to provide a layer of damp-proofing fluid. Although this ensures a better distribution of the damp-proofing fluid it is time consuming.
Slurry injection – (e.g. Vandex Injection Mortar dpc)
This involves drilling 18-20mm holes along a mortar line, approximately 230mm apart, from both sides of the wall and at an angle of about 30 degrees downward to a depth equivalent to the wall thickness. The holes on either side are staggered to give an overall spacing of 115mm. Water is then flushed into the holes to remove any dust. The damp-proof injection mortar is then mixed with water, enough to last 30 minutes otherwise it will solidify, to form a smooth paste which is then injected into the holes with a caulking gun. A reaction between the salts in the structure, moisture and the chemical results in a crystaline growth which will block all pores and fine cracks in the wall. This creates a solid damp-proof barrier through which moisture cannot pass. This method is advantageous for thick walls and stone walls which may be unsuitable for pressure injection, however it is messy and time consuming and results in unsightly plugged holes!
Structural engineers are involved in the design and construction of a range of structures such as office blocks, housing developments, hospitals, schools, bridges and tunnels. They often work alongside architects and are responsible for working out how buildings and structures will be made to stand up to the stresses and strains placed upon them. They have to ensure that a project is designed and built to be visually appealing, meeting all the necessary safety requirements. Work may include producing design solutions, meeting with clients and other members of the design team to discuss plans and preparing drawings and building specifications.
Now known as a Building Survey (see above). The surveyor examines the property externally such as chimney pots/stacks, roof coverings, soffits & facias, gutters and down pipes and external walls to see if there is any current evidence of settlement or subsidence. He will examine windows & external timbers, endeavor to identify a damp-proof course, will lift inspection chambers to examine drain runs. He will examine the site to identify any visually apparent problem with the boundaries. He will also advise if trees present a threat to the stability of the building. He will examine inside lofts to inspect the roof structure, the insulation, water installations and chimney stacks, checking that there is adequate support. He will check internally for cracks or signs of settlement of subsidence. A damp test will be carried out to ground floor areas. This can give an indication of whether sub-floor timbers are at risk of dry rot or wet rot. He will also inspect timbers, plumbing, electrics and heating. If there are obvious problems he may recommend specialist damp & timber reports to be carried out.
Timber decay occurs in timber which becomes wet and is attacked by one of a number of wood-destroying fungi. It always arises because the wood has become wet (above 20% moisture content). Finding the source of dampness and eliminating the ingress of moisture is always necessary. (see fungal decay above).
Toxic Box (Perimeter Box Treatment)
Four sided “containment barrier” provided to contain dry rot mycelium within an area of wall by introducing a masonry biocide through the full thickness of a wall, combined with a surface application over the area contained by the perimeter. This is used to protect masonry adjacent to a dry rot outbreak. (see also Cordon Sanitaire above). “Toxic” is an emotive word as the masonry biocides used for dealing with Dry Rot are not classified as toxic, therefore Perimeter Box Treatment is the preferred term.
A government backed initiative to help consumers find reliable and trustworthy tradesmen. Every firm’s technical skills have been independently checked through on-site inspections. It is widely supported by consumer protection organisations and the building industry.
When you formally apply for your mortgage, they will arrange a basic valuation report, to check that the property is worth enough to support the amount you want to borrow. The fees for valuations are generally set by the lender. This report does not go into any real detail on the state of the property, so you may want to instruct a surveyor to carry out a more detailed inspection for your own peace of mind. There are two types to choose from: Homebuyer report & Building Survey. (See details under relevant headings).
Vernacular Buildings & Structures
Vernacular rural buildings, such as byres, mills and kilns, are an integral part of United kingdom’s cultural heritage and contribute to landscape and local character in rural areas. These rural buildings were usually built using local materials and traditional techniques, and many pre-date the advent of mass-production techniques and the use of new building materials such as concrete. Examples of vernacular buildings / structures include simple farm or estate buildings, byres, mills, kilns, smiddy cottages, workshops, dovecotes, boundary walls, drystone dykes, ha ha’s, walled gardens, bridges, green houses, Dutch barns, gate piers, statues, fountains.
Water proofing (Tanking)
It is common where walls and floors are located below ground level for ingress of either dampness or even running water. This lateral and rising damp penetration is caused either by capillary action or by hydrostatic pressure. The term for overcoming such waterproofing situations in cellars and basements is ‘tanking’. A good tanking system can perform well enough to enable cellars and basements to be transformed into habitable living rooms and bedroom areas.
A trend over the last decade has evolved whereby property owners are actively having basement areas added to houses which were originally built without them. This has become very much the vogue in areas of high property value such as London, where in some areas there is hardly a street without several houses having ‘basement creations’ constructed. Whilst the techniques for adequate waterproofing of new basements is excellent, the disruption and diversion such operations can have on the local water table, are in some cases inadvertently causing neighboring properties significant damp and flooding problems.Tanking traditionally took the form of an asphalt lining applied to both the basement walls and floors. Today the method more often constitutes a cemetitious render coating or a cavity air gap membrane.
Wet rot is a wood destroying fungus and is a common cause of structural timber defects. It requires a moisture content of 50 to 60% to survive. It does not spread through masonry and growth will stop when the source of moisture is removed.
Timber affected by wet rot darkens, with cracks running along the grain of the wood and minor cracks appearing across the grain. These are usually less deep than those caused by dry rot.
Woodworm wood boring beetle Insect Infestation
Common Furniture Beetle/ Woodworm / Anobium Punctatum
The most common wood destroying beetle found in British buildings today is the Common Furniture Beetle Anobium punctatum. This insect commonly occurs outdoors infesting dead tree trunks, branches and other forms of exposed timber but, the main cause for concern is its ability to infest indoor roofing beams & floor timbers in a variety of situations. Adult beetles emerge from timber in the spring and summer. Very soon after mating the female beetle lays approximately 30 eggs, often into cracks and crevices in the timber she has just vacated. Usually within a month the eggs hatch and the young grubs begin burrowing into the timber. Here they remain for between two and four years slowly eating and burrowing beneath the surface of the wood. Eventually the mature lava excavates a pupation chamber just beneath the surface of the wood. Following the pupation process the adult beetle cuts a hole in the surface of the timber and emerges to start the process once more. It is the appearance of new emergence holes and the dust (frass) that falls from them that often indicates the presence of an active infestation of wood boring insects.The woodworm beetle is significant because given the right conditions it can infest a wide variety of timber products including structural building timbers in roof lofts, furniture, and wooden ornaments. If left unchecked wood boring insect infestations can lead to severe structural weakening and eventually total collapse.
Basement Waterproofing Converting damp basements and other spaces below ground level into dry rooms can be a cost effective and highly rewarding way of extending a home or utilising space within an existing property.Many members of the Property Care Association specialise in the provision of waterproofing systems that are employed to upgrade existing basement rooms, waterproof new buildings or convert damp, unused spaces below ground into dry habitable rooms.Structural waterproofing below ground is a highly specialised operation and must be undertaken by contractors and designers who have the requisite levels of skill, understanding and experience. Failures resulting from inadequate specifications or poor workmanship can be very costly. PCA members who specialise in structural waterproofing are able to work with the client to design a suitable waterproofing solution.Waterproofing in existing underground structures is usually undertaken by applying waterproof membranes to the inside walls and floors or by using drained cavity technology.Waterproofing techniques are defined in BS8102, the British Standard for “Protection of structures against water from the ground”. Members of the PCA must demonstrate an understanding of this standard and the Association’s code of practice for underground waterproofing. The PCA also requires that surveyors providing guidance on waterproofing must demonstrate their competence by gaining the “Certificated Surveyor in Structural Waterproofing” (CSSW) qualification.Structural Waterproofing SystemsThe two types of waterproofing system commonly used in existing structures are:
Adhered waterproof membranes or “Type A” waterproofing systems (as defined in BS8102) are commonly multi coat renders, cement based coatings, bituminous paints or epoxy coatings. This form of waterproofing provides an unbroken barrier to water. These systems are applied to clean walls and floors and are usually protected and held in place by floor screeds, renders, plasters or other “loading coats”.Cavity drainage systems or “Type C” waterproofing usually utilise pre-formed high density drainage membranes, channels and sumps. These are designed so as to direct any water entering the structure back out in a controlled and managed way.Typically cavity drain membranes are installed to the walls and floors these direct water into drainage channels. The channels then allow water to be directed to sumps or drains so that it can be removed safely from the building.Members of the PCA who specialise in structural waterproofing are able to consider the nature of the building and the clients design requirements to ensure that the correct method of waterproofing is selected and executed to the highest standard.
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