Treatments for Dry and Wet Rot
Any outbreak ofneeds prompt, thorough treatment. Defective plumbing, faulty damp-proof courses and blocked air bricks or similar faults must first be rectified. Also, replace any broken air bricks and clear blocked ones. If the house has been flooded, or have soaked timbers, check that the wood has dried out thoroughly.
Even if the location of any outbreak may seem obvious, make a systematic inspection inside the house. Look for signs of surface buckling of the timber and test with a sharp knife or tool.
Inspect beneath the floorboards for the signs of decay listed earlier. If evidence of an attack is found, consider that point as being the centre of a sphere, having a radius of about lm, and make an extremely close examination in every direction within this area.
Whenever continued evidence of decay is found, extend the ‘sphere’ principle of investigation until the limits of the attack have been found and the causes traced.
All timber in the affected area and lm beyond the last visible evidence of decay must be cut away, provided this does not weaken the structure. If there is such a risk, seek expert advice. Any plasterwork or rendering coats which have been penetrated by the fungal strands should be removed.
The whole area of attack should be opened up, thoroughly cleaned down with a wire brush and the decayed material removed from the building by the shortest possible route.
All affected timber should be burned immediately and any plaster sprayed with a fungicide such as Rentokil Dry Rot Fluid. These measures are vital to avoid further infection spreading to other areas of the building.
If masonry is affected, drill a series of holes covering the contaminated parts at staggered centres to allowfluid to saturate the affected area. It will then reach all possible mycelium within the masonry. Working from the highest level downwards, apply a good proprietary fungicidal fluid to all brick, block concrete and earth surfaces until they are satu-rated; 5 litres of fluid to 4.64m, for surface treatment, is normally adequate when applied with a coarse spray.
If the fungal strands have penetrated the brickwork or masonry, then both sides of the wall should be treated by the hole-drilling process.
All replacement timbers must be thoroughly treated with a fungicidal wood preservative, and the sawn ends steeped in the fluid for at least five minutes before installation. Any joist ends are best protected with fungicide, plus a coat of bituminous paint, before setting these into a wall.
Apply two liberal coats of fungicidal fluid to all timber surfaces adjacent to the area of cutting away, to a distance of l.52m from the furthest extent of the cutaway timber. Allow the first coat to be absorbed before applying the second. Five litres per 18.58m2 should be applied.
Allow any brickwork or masonry to dry out completely before redecoration or re-rendering. It is advisable to apply a 6mm thick coat of zinc-oxychloride plaster over the rendering coat before applying the finishing coat of plaster.
This zinc-oxychloride coat should extend 300mm beyond the limits of the attack to inhibit fungal growth. Any areas not to be replastered, can also be treated with two coats of zinc-oxychloride paint.
The treatment of wet rot is less drastic than that required for dry rot, and as long as the cause of dampness is removed and the timber allowed to dry out, no further growth of the fungus will occur.
Test all the timbers in the area of fungal attack with a strong, pointed instrument to determine the extent of sub-surface breakdown. Cut out and burn all timber which has suffered surface or sub-surface breakdown due to fungal attack, together with any dust, dirt and general debris.
Select thoroughly dry, well-seasoned timber for replacement. Cut it to size and apply two liberal coats offluid on all the surfaces and also over the adjacent existing timbers, and on brick, block and concrete areas before replacement timbers are fitted. This pre-treatment of new timber is a vital part of any remedial work and must be carried out after the timbers have been cut to size.
If an extensive outbreak of rot is suspected – especially with dry rot – it is wise to consult a reliable specialist timber preservation company, which will conduct a free survey, submit an estimate and report without obligation, and issue a 20-year guarantee on completion of any work.
10. November 2011 by admin
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