dry rot

16 Nov 2004
Reaction score
United Kingdom
have a case of dry rot on a job. have stripped back all the rotten timber lintels and rafters in the process of replacing with concrete and treated timber.
im going to ventilate roof void, as it isnt vented at present.
whats the opinions on professional chemical treatments , as i know the guarantee becomes void if moisture is present in any situation.
what i had planned to do is :
wire brush all visible signs of dry rot on masonry, then spray with cuprinol dry rot treatment on surface.
anyone have any opinions?
Sponsored Links
Its a bugger really the cuprinol treatment won't be any better than the commercial stuff, but probably will be just as effective.
As you already know damp conditions are the main enemy here.
Its always difficult as you will never irradicate all the spores but I would wash down any masonary with something like jeyes fluid before you wire brush to try and keep the spores down and then spray.
Just sorted a dry rot problem (fingers crossed ) for the father-in-law it had started in the cellar and spread up to the ground fllor joists and then got up behind some panneling in the lounge into the first floor joists and again up behind the panelling upstairs but luckily hadn't got as far as the attic.
Took out two skip fulls of dammaged timber and infected masonary, before washing down and spraying everything in site.
Perhaps you can detail the job a little further:
1. What was the cause of the damage in your opinion?
2. How do you know that it is true "dry rot"?
3. What was the extent of the damage?
4. Is the wall(s) involved cavity or solid?
5. Have you investigated below and to the sides of the area in question?
6. Why concrete lintel(s)?
I can certainly help you with your question but i would need a little more info, true dry rot or "serpula lachrymans" as the reports like to elevate it, can be a tenacious and difficult business to eradicate.
thanks for your response.

1.previously repaired leak in annexe roof
abutment to main building.
2.charred timbers and spread of thread like network throughout mortar and behind bricks. not too thick though!
3.timber lintels were eaten through on the sides closest to the probable leak, and timber partition which had been partially repaired but not enough in my opinion. rot seemed to be dormant and didnt seem to be recent growth after repair some 5 years ago. this damage has only been seen as i am fitting a bathroom for my client.
4. wall is brick cavity. i have exposed the external by taking away the internal 2 courses to replace the rotten timber lintel.
5.i have taken off all plaster to the sides of the affected area, and im pretty confident i can see the full extent of the area.
6.concrete because the sixe of the timber lintel in relation to the span was not sufficient in my opinion,plus i erred on the side of caution with regard to a possible further outback.
Sponsored Links
You seem to have it well covered and chappers has indicated options.
Steel angle iron is often the best option for a retro lintel installation. Never use timber lintels . Period.
It sounds like "dry rot". You can buy a larger, cheaper container of treatment fluid from one of the chemical companies, you might also require some "mayonnaise" paste for treating woodwork. Use a mask and be fire alert with the spraying.
As regards remedial plastering , go sand and cement render with a chemical inhibiter and say, Limelite skim.
Dont guarantee anything. Period.
By and large, the removal of moisture and a drying out period is the best guarantor that the fungus will remain dormant, but its not a certainty.
Hope this helps. Come back if you want any more info.
Note: as a matter of interest, a leak and consequent infection in the roof of a 5 level pub resulted in the total hollowing out of the structure - basement to roof, all timber and plaster was removed and replaced. Three years later another infection "broke out". Beware.
thats always the case the larger the spread of infection usually the harder it is to totally eradicate i would advise removing as much of the material in the infected area as is practably possible.
I have been told there is a smell that can be a giveaway there is dry rot present.

Can anybody describe the smell. I have been musty but not sure what that means. Does musty mean it smells like a wet towel that has been left wet and in the cold for a few months.

There is a smell in my house which I suspect is mouse urine. Could the dry rot smell in anyway resemble mouse urine.
I have a vague idea that the smell of dry rot is acetic acid (vinegar), probably mixed in with other stuff. Apart from the rotten wood itself, which tends to break up into cuboids, two other tell tale signs are:

1) A fine rust coloured powder (spores) drifting out of crevices.

2) Mushroom coloured strands (mycelium) spreading up your walls in search of new wood.

If you find a mycelium strand terminating in a large, spongy pad covered in brown spores (a fruiting body) that's conclusive! The insidious thing about dry rot is that it only needs one damp patch. The mycelium carries the water to dry wood and wets it so that it can grow there too. With its feet in a bit of wet timber under the floor it can spread all the way up into the roof and eat the lot.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links