Rot is one of the major causes of timber decay in properties and will usually found be found where dampness from any source has been allowed to become established for a period of time, thus creating the ideal conditions for wood rot spores to germinate and spread as a fungal infestation which progressively destroys the structural integrity of all types of timber.
The correct identification of dry rot is important owing to the extensive and elaborate measures necessary to control and eradicate it. The recognition of the various diagnostic features of the timber, mycelium, the strands and fruiting body is important for a positive identification appraisal.
Timber is a cellular material consisting mainly of cellulose and lignin, which provides the timber with rigidity and strength. Dry rot breaks down the cellulose of the timber leaving behind the lignin, which gives the timber a darker colour. This darkening is characteristic of “brown rot”. As the wood breaks down it loses strength and weight and cracking and shrinkage occur. It may also appear warped. The decayed timber splits into cuboidal pieces with deep cracks along and across the grain caused by the shrinkage.
Fungal growth is dependent on the development of the hyphae, the fine filaments which elongate and spread through and across the damp timber As the hyphae grows, it forms a larger mass, the mycelium, which can appear as a white, fluffy cotton wool like growth or silvery grey sheets. The mycelium can also be tinged with lemon yellow and lilac patches. The skin or sheet will peel back like a mushroom cap in straight lines. A musty mushroom-like smell may be present especially when conditions promote activity.
White or grey strands, which conduct nutrients and water are formed within the mycelium. These strands, which can be up to 8 mm thick, will allow the fungus to spread over and through inert materials and reach further timbers. This ability must be considered when inspecting a dry rot outbreak. The strands will become brittle on drying and will “snap” audibly. This brittleness will distinguish the strands from other similarly coloured wet rot stands.
The fruiting body can be the first indication of dry rot although its
development usually follows advanced growth. Shaped like a fleshy pancake or bracket the fruiting body has a centre section covered with wide pores or folds, orange or reddish brown coloured from which spores are produced. These rusty red spores are released into the surrounding area and disperse on air currents as a red dust settling on horizontal surfaces.
Where dry rot is present the inspection must be carried out carefully and methodically. Remove affected skirting boards and floorboards and examine the sub floor area, checking for fungal growths and testing the joists by prodding with a screwdriver or similar implement to determine the depth and extent of decay. Assess the sub floor ventilation checking for a musty mushroom like smell, which may indicate activity and debris, which may promote the spread of the fungus or the germination of the spores. Check the plasterwork adjacent to areas of decay by removing small pockets to determine the spread of strands behind the plaster. If necessary remove random bricks to examine the cavity for any signs of the fongus.
Determine the cause and source of dampness and rectify to promote drying conditions, paying particular attention to rainwater goods bad pointing flashings and bridged damp proof courses.Where dry rot comes into contact with a party property the owners or occupier must be notified and if possible an inspection carried out.
The principal aim in the control of dry rot is to identify and eliminate the source of moisture and dry the building as quickly as possible to reduce the moisture content in the timber to below 20%. This procedure may take a long time and although it forms the basis for eradicating the fungal infestation secondary measures may be required to prevent further damage.
Cut out and remove all decayed timber up to 600 mm beyond the visible limits of fungal decay depending on site conditions and severity of the fungal growth.
Remove all built-in timbers, e g. wall plates, lintels, bonding timbers within the affected area and replace using steel or concrete.
Remove all timber debris from the sub site area and any surface fungal rowth, which may be on exposed areas of masonry.
Rake out mortar joints in areas where masonry sterilisation is required and carry out a thorough surface treatment using a coarse spray of Palace fungicidal irrigation fluid applying two or three treaments. This treatment is essential to ensure all residual spores from the infected timber are eliminated to isolate an existing outbreak and prevent any future recurrence. of dry rot by constructing a “cordon sanitaire”,using a method of drilling and injecting irrigation fluid into masonry or brickwork to form a sterile barrier located as follows:
a) Between an outbreak and timber in the immediate area which is not affected,
b) At the base of a wall with no DPC membrane where established in infected wood beneath a solid floor,
c) To brickwork where fungal decay by dry rot has affected timbers or masonry in a party wall with adjacent property,
d) To isolate and protect built in timbers which may be affected by are not readily removable.
Re-plastering of exposed brickwork should be carried out using Palace Fungicidal Waterproofer especially in areas where a severe infection is evident or in a party wall situation where access is not available to both sides of the wall.
The replacement timbers should be pressure impregnated and cut ends retreated using Palace Universal Wood Preservative
timbers Palace Timber-treat Ecology. The ends should stand in the
preservative for a minimum period of one hour to ensure penetration up the end grain. Residual sound timber in the area of the outbreak should be cleaned and treated using Universal Wood Preservative
To prevent any future recurrence of a fungal outbreak it is important that the property is well maintained to prevent any ingress of damp and all external protective measures are kept in good order
Palace Chemicals Approved Installers are vetted and trained and approved before they can offer the Tallgrove 30 year Assured Guarantee. Site visits while work is in progress ensure that our Contractors carry out the work to a high standard of workmanship and professionalism before they are considered Approved Contractors who can then offer the Tallgrove Guarantee. Palace Chemicals have gained a reputation for quality of its products, service and Installers for over 30 years offering assurance to Building Societies, Housing Associations, Councils and the public with the Tallgrove Assured Guarantee.
The cover offered by the Tallgrove Assured Guarantee is by a single payment of 5% of the contract price, subject to a minimum premium of£15.00 plus VAT. When a property is sold, the guarantee remains valid and the benefit of the guarantee is transferable to new owners on completion of sale, a service provided without additional fees. Simply notify Palace Chemicals of details of the new owners in duplicate and we will countersign the notification and return a copy for your files to retain its’ validity.
The approved installer guarantees the treatments for the following treatments which should be clearly identified on the installation map provided with the guarantee:
• Timber infestation by wood boring insects or infection by woodrotting fungi or rising damp for 30 years.
• Effectiveness of the installed damp-proof membrane against rising damp.
• Re-plastering carried out above the DPC as per the details on the guarantee plan.
Although this cover is provided by the approved installer, should he cease to trade, Palace Chemicals will procure the carrying out of any necessary treatment work by another Approved Installer under the terms of the guarantee. The extent of the required work will be determined following an inspection by Palace Chemicals which will be subject to an inspection fee, refundable should the claim be valid.
The Guarantee is valid only in the event of the re-occurrence of rising damp during the period of the Guarantee providing the area concerned is specified on the plan. Failure to observe the following precautions will invalidate the guarantee.
• All surrounding structures and materials in contact with the exterior walls of the property must be kept to a minimum of 150mm (six inches) below any damp-proof course installed and exterior rendering must terminate above the damp-course level.
• Defective guttering, downpipes, soak-aways, etc., which cause excessive concentrations of moisture must be rectified or repaired.
• The base of exterior walls must be kept free of moss, lichen, etc.
• Water butts or similar receptacles receiving water from guttering or downpipes must be properly maintained and provided with an overflow to be discharged at a distance from exterior walls.
• Wallpaper, vinyl paints, textured paints or any other decorative finish which is likely to restrict normal drying out after DPC installation must not be used for a minimum period of 9-12 months. Only water based emulsions should be used.
• The damp-proof course should not be damaged or interfered with by any other building works or structural modification.
Claims under the Tallgrove Guarantee can be admitted only upon production of the original document bearing the company seal of Palace.
The Palace Dampshield 10 Year Joint Tanking Guarantee is issued jointly by the installer and Palace Chemicals for tanking treatments carried out using Palace Dampshield Waterproof Tanking Slurry. This guarantee is also based on a premium of 5% of the contract price but is only valid for the period of 10 years following installation of the tanking compound.Like the DPC guarantee, the areas treated are identified on a detailed sketch showing quantities used, method of preparation and length and height of areas treated. Failure to observe the following precautions will invalidate the 10 year joint tanking guarantee:
• Any other essential work specified in the survey report shall be completed in reasonable time in accordance with sound building practice.
• The client (or his successor owner) shall be responsible for the full and proper maintenance of all water systems in and around the property.
• Re-occurrence of dampness due to defects in or originating in adjoining properties or structures shall render this guarantee invalid for the affected area.
• Subsidence, movement or other local structural factors altering the fabric of the property and its’ surrounding water table following installation of the tanking will invalidate the guarantee
This final category is not covered by Palace Chemicals Ltd, since under the terms of this certificate, only the fluid supplied by Palace Chemicals to be installed as the DPC is subject to a warranty.
This guarantee is issued free by the installer without any payment or premium being made to Palace Chemicals Ltd and no responsibility or liability for the work carried out during installation is taken on by Palace.
All structural work carried out to install the damp-proof course remains the full responsibility of the installer and this liability is not transferrable should the installation company cease to trade. Any issues reported against the 30 year Joint Guarantee should be directed entirely towards the installation company, who if still in business will be bound to the terms outlined for the full guarantee cover period.
All tile fixing should be carried out in accordance with BS 5385:
WALL & FLOOR TILING Part 3 1989 – Code of practice for the design & installation of ceramic floor tiles and mosaics. Section 14.4 of this standard emphasises the need for timber substrates to be more than suitable for carrying the expected load and the be then stiffened prior to tiling. Ceramic floor tiling should never be installed amic on floating timber floors subject to heavy static or dynamic loads.
The latter point emphasising the fact that a timber base alone may allow deflection, which is beyond the tolerance of the ceramic covering to be applied, therefore the need for rigid sheeting and screw fixing is essential to ensure stability and rigidity.
Floating floors by definition are not fixed to the base substrate, therefore before tiling a floating floor it is essential to determine that its’ structural stability is sufficient to meet the requirements of BS 5385, part 3, section 14.4.
A typical floating floor lies on a concrete base and is characterised by a layer of rigid insulation topped with flooring grade plywood or chipboard (18 – 20mm deep) The insulation layer should be of sufficient density to provide firm support to the over over-laid board. Expanded polystyrene is not considered to be a suitable underlayment for a floating floor which is to receive ceramic. To further ensure the rigidity of this structure the timber board can also be constructed as a raft fixed onto timber battens (45mm x 45mm), with the insulating material laid between the battens.
To prevent excessive deflection it is essential that the board is 18 – 20mm thick and that the insulating material is sufficiently dense and rigid to support the expected load without risk of excessive compression or movement.
Joints between the sections of chipboard should be tongue and groove located and bonded with a waterproof wood adhesive. Any ded joints between adjacent boards must be fully supported as butt butt-jointed edges to prevent deflection between the two.
All timbers used in the construction of the floor must be moisture stabilised to the conditions expected within the finished location. expected Moisture stability should be further protected by the installation of an effective damp-proof membrane within the base structure and proof sufficient heat and ventilation to control humidity within the service environment.
Timber surfaces receiving tiles should be clean, dust-free and clear
dust of any surface coatings likely to impede the adhesive from forming an effective bond to the surface. The use of Tilers’ Primer (SBR) is also advised on all worn or porous timbers & composite boards.
The base substrate must also be even, level and stable, with no localised depressions or elevations likely to cause uneven compression of the insulation layer.
Where the above precautions have failed to secure a stable surface,
free from deflection and movement, it will be necessary to over lay
ection the existing board with water-resistant plyboard to a minimum 18mm resistant thickness, laid with staggered joints. Also battens to support the boards should be fixed to the base substrate at 300mm centres and then install the insulating layer and over-laying boards prior to tiling.
NB: Do not proceed to fixing tiles if after all preparatory measures have been taken the floating floor still shows signs of deflection or movement likely to exceed the rigidity required by the ceramic tiles when subject to the anticipated loading.
part Use Palace Super-Flex two-part adhesive laid using a floor grade
notched trowel to achieve a solid adhesive bed of not more than adhe
Use Palace Flexi-grout for joints from 3mm up to 20mm wide. In grout situations where heavy trafficking is likely to result in more movement, flexi-grout mixed with Palaflex additive (pre-diluted 1:1
grout (pre with water) will provide even greater movement tolerance. Note all polymer modified grouts should be cleaned from tile surfaces within ified 1 hour of being applied as they can be extremely difficult to remove when set.
It is essential to ensure that the full perimeter of all floating floors is sealed with a silicone sealant based movement joint to a minimum of lant 6mm width (In accordance with BS 5385: Part 3 – 1989, clause 19 to
23). This requires joints at all perimeters of the tiled area, coincidental with existing structural movement joints in the substrate and across large floor areas at 8 to 10m intervals.
It has become increasingly necessary to point out that it is virtually impossible for the dry composition of the pre pre-blended grout powder to produce localised variations or patchiness in the appearance of the applied grout without first having been affected by any one of the atchiness following factors, all of which are beyond the control of the manufacturer.
It is essential to ensure the powder is mixed thoroughly an and consistently in a clean vessel, with clean water, to form a smooth, homogenous and lump-free paste. Consecutive mixes of the ready to free
apply grout must be produced from the same batch of powder, using an identical water addition, whilst again achieving a fully consistent, smooth lump-free paste and never add more water than the free recommended addition level.
All joints to be grouted must be of consistent depth and raked clean of any adhesive residues as any contaminant in the open joints will consequently result in irregularities in the depth & consistency of he
freshly applied grout, both of which may result in shade variation.
Immediately after grouting when wiping down to remove the excess from the tile face around the joints, care must be taken not to “over “over-wet” the freshly compacted joints, as this may affect water content in some joints but not in others, leading to a higher concentration of fine surface laitance and hence raising the possibility of a lighter shaded lity appearance in these areas.
Brushing or dry-wiping over a grouted floor joint when the paste has wiping dried and bodied up, but is still not set can disturb the surface finish and open up the texture of the grout to give a coarser and darker shade than when the grout was first laid and finished off with a wet cloth or sponge. Any contact with the surface at this point in time must be even and consistent over all areas to ensure the hardened appearance retains an equal texture, otherwise shade variations are inevitable.
Cleaning and maintenance of the completed tiled surface must ensure that the materials and cleaning agents used are applied consistently, are not used at excessive concentrations and are rinsed off promptly as soap and detergent residues can accumulate in joints and affect appearance, particularly when exposed to moisture.
Variations in the density or porosity of the surface beneath the tiles will encourage some areas of the grout joints to dry out at a different rate to others, usually illustrated where darker areas of the grout are laid over dense or impermeable section of flooring, whereas lighter shades will be evident over the more porous and drier sections of the substrate flooring.
The end use of the tiled location needs some consideration as this may result in some areas being exposed to wetting more frequently than others, which consequently will result in the damper sections appearing slightly darker than the drier areas. Regular and localised wetting of one area at a more frequent rate than the surrounding tiled area will result in a shade variation due to the moisture level retained within the cured tile joint.
Porous tiles, substrates or joints adjoining the cut edge of a tile will be exposed to greater risk of moisture absorption from the wet paste than less porous surfaces or true tile edges. This can produce localised variations in moisture content and when fully cured will manifest in a shade variation from joint to joint.
To maintain an ideal consistent appearance in all grout joints it is essential to ensure consistency is applied at all stages of the application process, including the type of tooling used to finish off joints, the amount of moisture introduced when cleaning the tiled surface and the finish time which elapses between initially compacting the joints and then returning to tool the joints to a smooth clean edged fini Failure to finish. Adhere to any one of the above precautions is likely to result in hade variation in the final colour of the hardened grout, which may only then resolved with the application of a mildly acidic surface cleaning agent
All tile fixing should be carried out in accordance with BS 5385: WALL &FLOOR TILING Part 3 1989 – Code of practice for the design & nstallation of ceramic floor tiles and mosaics and the Tile Association guide – “TILING TO TIMBER SHEETS BOARDS & TIMBER SUBSTRATES. Section 14.4 of BS 5385 part 3 1989 emphasises the need for timber substrates to be more than suitable for carrying the expected load and then be stiffened prior to tiling.
The moisture content of timber can vary depending on the temper temperature and humidity conditions depending on it’s storage location. To ensure dimensional stability of structural timber it is essential to allow time for the moisture content of the wood to form an equilibrium with the ambient conditions of the environment where it is to be permanently installed. Composite wood boards will stabilise to lower moisture contents than is the case for solid wood structures.
Timber should be conditioned to suit its’ intended environment by storage for a suitable period of time until the moisture content stabilises to an acceptable level. The table below indicates the normal “in “in-service” moisture contents for softwood timbers, studwork & battens:
|Conditions||% moisture in Softwood timbers||% moisture is composite boards|
|Unheated||15 – 19%||Up to 15%|
|Periodic heating||10 – 14%||9 – 12%|
|Continuous heating||9 – 11%||7 – 9%|
|Under-floor heating||6 – 8%||5 – 7%|
Failure to ensure the moisture content of structural timbers is within the ranges shown above could result in dimensional changes which can adversely affect the stability of any bond between it and rigid ceramic or stone tiles.
Tongue & Groove Floorboards should be fixed directly onto joist spaced no joists more than 300mm and should only be tiled over using 2-part Super-Flex adhesive
Plywood is available as “wood based panel” or shuttering ply (as defined in BS EN 313-2) however Marine Plywood (BS 1088) is more durable, water 2) resistant and hence suitable for tiling. WBP Plywood (Water & boil proof) is similar to Marine ply but has no BS classification.
Particle board (Chipboard) is defined in BS EN 309 and is an adhesive bound agglomeration of wood particles suitable for receiving tiles only in permanently dry areas
All of the above types of timber board when used for flooring must be a minimum of 15mm thick and screw fixed over stable battens at no more than 300mm centres to be structurally acceptable for fixing over with ceramic tile adhesives.
Multi-Layered Strand board (OSB board) as defined in BS EN 300 are oard) suitable for tiling usually on wall surfaces. They are generally 11mm to 18mm thick, bound with a strong adhesive and incorporate water repellent components to provide improved moisture resistance
WALL TILE FIXING:
The use of sheets and boards that are still subject to movement from changes in moisture content should be avoided it at all possible and the exposed backs and edges of boards should be sealed against the ingress of seal moisture to reduce the risk of movement and warping. In general where a sheet or board has a smooth or rough side, the latter should be used as the receiving surface for tiling.
Joints between boards should define the position of movement joints and should not be bridged over with tiling. (BS 5385 part 1). Mechanical screw fixings of appropriate dimensions should be used to secure all types of boards to rigidly stable and secure battens, frameworks and noggins. NB. On wall surfaces heavy duty stone tiles should not be fixed to fibreboard or chipboard. FLOOR TILE FIXING:
Existing timber bases should be sufficiently strong & rigid before they are to receive tiling and be checked that they are capable of carrying a static load (up to 0.8Kn/m2) and a dynamic load without perceptible deflection. Stiffening the floor with new joists or additional noggins may be required where deflection is detected.
Ventilation beneath the timber floor must be provided for by air bricks or similar means. The appropriate grade of board for flooring will be a minimum 15mm thickness of either Marine or WBP plywood (BS5385 part 3) with the exposed back and edges protected from moisture ingress with a water resistant sealer (Tilers primer SBR is acceptable).
Counter sunk screw fixings at a minimum 300mm centres should secure the unter boards to joists and noggins where joints between boards should also be coincidental with the support below.
Boards in areas where frequent wetting is likely (showers & wet-rooms) should be protected by the application of a waterproof membrane (Palace Shower-tight) or an un-coupling membrane before fixing proceeds
Adhesives should be selected which are recommended for use over timber substrates. On walls D1 or D2 ready mixed dispersion adhesives can be used with selection depending on the degree of exposure to moisture. Cement based adhesives should be classified to BS EN 12004 C2. Palace Multi-Flex, Easi-Flex & Trade-Flex are all suitable for fixing to timber boards on wall & floor elevations. Super-Flex 2-part flexible adhesive should be Flex 2 used on tongue & groove or floating timber floors
Use Palace Flexi Wall & Floor grouts for joints from 3mm up to 12mm wide. Note all polymer modified grouts should be cleaned from tile surfaces within 1 hour of being applied as they can be difficult to remove when set.
It is essential to ensure that where tiling is coincidental with a floor joint or a change in floor surface type that a movement joint is formed with a silicone sealant to a minimum of 6mm width (In accordance with BS 5385: Part 3 -1989, clause 19 to 23). This requires joints at all perimeters of the tiled area, coincidental with existing structural movement joints in the substrate and across large floor areas at 8 to 10m intervals.