Judging by the second picture it is dry rot. You don't always get a fruiting body - I've seen plenty of rampant dry rot and not a mushroom in sight. You do often get the stringy white rhizomes - particularly visible when you cut out the infected wood - it runs along between the brick and the wood. by law you are meant to cut out all timber 1metre beyond the any evidence of the dry rot and replace. The adjoining walls should be treated and treated timbers used in the repair. You can be held responsible if at a later stage your dry rot invades a neighbour's property so it is especially important to properly deal with any dry rot on or near a party wall. dry rot spores lie dormant for many years/decades waiting for the right conditions ie 40% moisture or above
Having suffered wet and dry, I'd vote for the wet. Common factor in the dry rot I've come acoss, is that the infected wood looks warped/anorexic in all axes and runs some distance from the starting point. The pics show rotted wood but still holding it's initial shape.
Dear Tim The fungus is unquestionably a brown rot but as dry rot is also a brown rot that does not help! The photographs have most of the characteristics of wet rot and none of dry rot. The white part looks to me like a sporophore of C. puteana (one of the wet rots). The reasons for my opinion are: a superficial hard outer skin about 0.5 to 1.0 mm thick the absence of obvious hypal strands the absence of visible mycelial strands the confined location the characteristics of the location (in a roof timber without the necessary lime mortar for dry rot) the history of past leaks
To answer and dispel some of the comments and assertions made by others Serpula (with an "e") lacrymans has no requirement for a high temperature and most strains have their optimum at 26 C and are controlled/killed only a few degrees above that - hence the lack of it in the outside timbers of south facing windows Coniophora - cerebella/puteana actually has a higher optimum growth temperature
You only have to remove unsound timber if the timber cannot fulfil its structural role I concur with the opinion that if there is a bit of rot and it is not fulfilling any structural role it can be left in It is good sensible practice to isolate from timber with a dpc and essential to instal ventiation and cross flow of air with cross battening if you can
Use a thin long drill bit to check for hidden decay in any rafters timbers about which you are concerned
Use only Tanalised replacements and dip treat overnight any cut end grain Put the tanalised end near the brick and the on-site treated end in the room
It is not worth "sloshing" any fungicide arouond - complete waste of money and not reasonable in a coshh assessement. Immersion of cut ends is the only effective use needed
Strands are for the purpose of conduction of nutrients from the hyphal front not water to it. The strands are thought to have evolved to reduce water loss in this process. Water at the hyphal front is abstracted from the atmosphere not along strands This was published in 1981 by DH Jennings at the University of Liverpool using C 14 glucose to follow the nutrients - mostly in trehalose. The conclusion was that one needed 95% RH for DR to flourish.
Meow2 is correct but that does not fix your structural problem or prevent recurrence if there is a new leak
Dry rot can only continue to "eat your house" (after the water source has been fixed) if the interstices are at an RH of greater than 95% and that only happens when the masonry is very wet and acts as a reservoir. it also has to be alkaline as cement mortar does not suppor the dry rot. This is not common so most dry rot dies when the water source is fixed. That is most - not all!!! If, however, you have active dehumidifiction you will cure it and after a year at normal ~RT it will die
I do not agree with Andrew G that the location is perfect for dry rot for the reasons cited above and specifically absence of lime mortar in the roof where the sporophore/mycelium is and the absence mortar to act as a reservoir
It does not carry water from one site to the other - read the Jennings paper.
There are plenty of fungicides available - how about boron for a kick off - but I agree that non is needed for sloshing. All on the market have passed efficacy tests or they would not get the licence!
I shall be interested to know which Parliamentary Act requires one to cut out a metre beyond as I have served on various committees such as the BWP(D)A / HSE consulation group prior to the introcuction of COSHH in the late 70s and am familiar with COPR, BRE digest 299 and BRs and have been working both academically (my thesis was at ICST on hemicellulose degradation by fungi) and practically since the late 60s and am unaware of such a law. Indeed I have spent most of the last 35 years promoting the complete opposite and opposing the con-men who propose such rubbish
snipped-for-privacy@atics.co.uk coughed up some electrons that declared:
Hi Chris,
OK
Check. That was what I found for the next 8" or so beyond the totally gone bit. Looked OK, but poking a chisel in showed the core to be rotted.
OK.
This is a north facing roof. Interestingly, I've measured 38C in the roof voids on the southern facing side, during the height of summer.
Whew! As I said, the mostly good bit on the far left would be a sod to remove as it goes behind a wall.
Yes - I was going to put the new section of plate on a DPC. I'll be sure to put plenty of ventilation in the fascia - the wind will be able to blow up into the main roof from this flat roof, and ultimately out some other vents.
Good idea.
Ah. So prior to then, a lot of misbelief was floating around.
OK
I've heard everything from a foot to 3 feet - mostly I assumed from companies offering remedial work!
Ah, not heard that before... I appreciated that they strands were taking nutrients back, but had also read (presumably incorrectly) that they also carried water to the front (which I presume is also needed for the digestion of the timber's cellulose by the fungus).
What would you say to the oft repeated advice that plaster should be replaced with cement based render? Quite often you see this done on solid walls with lime mortar. It would seem that this will make the process of the wall drying even slower?
What is the best way to apply the dehumidification - i.e. just running an ordinary room dehumidifier in the vicinity while keeping the side exposed, or are there other ways?
(got a feeling we did actually discuss that in the past - but never got round to doing anything. The current one does seem to get mistaken for a serious article from time to time even though it is in the Humour category)
I don't think you can dismiss the effect that easily - cement based mortars are far less likely to transmit moisture. As evidenced by the number of soft brick walls that spall the first time there is a frost after being repointed with an inappropriate cement based mortar (because the bricks get saturated and can't shift the water into the mortar as easily as they once did).
So a lime mortar will be more likely to admit moisture, even before you get onto the effects of its pH.
Except indirectly - lime mortar tends to imply an older building which may not have the advantage of modern understandings of the need for sub floor or roof ventilation hence more suceptable to dry rot if moisture makes its way into the structure, which the very age of the building increases the likelyhood.
" without the _necessary_ lime mortar for dry rot)"
was the quote, Yes its more likely No its not a necessary ingredient, so anyone reading this thinking oh its ok I haven't got Lime mortar so I cant have Dry Rot.
Dry rot isn't rampant, it spreads according to food source and moisture content. A maximum is generally regarded to be 1m per year and even then only under ideal conditions. Above 40% moisture??? More like above 22% and it'll grow!!
While it's been suggested dry rot spreads more quickly in warm conditions, it must be remembered that warm ventilated conditions imply dry wood where dry rot cannot grow!
Dry rot spores tend to last 3 years, longer in cold conditions, shorter in warm.
One charcteristic of dry rot is a brown dust. A very wet cotton wool like structure and shrunken and dry looking cracked timber. These pictures show wet rot!
If you've removed all signs of dry rot, it's unlikely you'd be responsible for any further damage though it would be reasonable to inform your neighbour so he can inspect his own timber. Dry rot tends to inflict volumes with no access!
Remember dry rot needs mosture. As long as wood is in a ventilated area it will not support dry rot. Moisture content is key.
No lime mortar or render is completely irrelevant to an infestation of dry rot, it can if conditions are suitable aid the spread to other adjacent timbers that would not initially been able to support the Fungi spoor germinating.
Serpula lacrymans is a naturally occurring woodland Fungi it survives well enough outdoors so ventilation alone is clearly not sufficient to stop it's occurrence, but the inside of a house can if the timber is able to support germination act as a wonderful petri dish regardless of age.
Answers to your two questions What is the best way to apply the dehumidification - i.e. just running
Isolate the rooms or areas from any other water sources by shutting doors and windows and sealing any porous walls such as internal stud walls by lining with polythene or the like and draught stripping provide dry heat install dehumidifer
It is often practical in buildings in the summer simply to open all the windows in the day and get solar gain and dehumify at night In the winter just do it all the time!
What would you say to the oft repeated advice that plaster should be
We never recommend removal of plaster unless it is covering up timbers that are damp or at risk Plaster removal is often overdone particularly in listed buildings where I go to great lenghts not to take it off if possible
If lime plaster is removed there is a cogent argument to put back lime I only use cement within 1 m of the ground when there is a history of hygroscopic salts contaminating due to years of rising damp or when the building is so modern that it matters not if you use cement
Cement will slow down the drying of the walls but equally it will provide an instant dry surface for putting on joinery timbers at risk such a skirtings or architraves and the water in the brick cannot therefore go out internally but has to externally even if it stays there it matters not as the plaster acts as a dpm
Well, overall, I'm happy to go with the majority vote that it's wet rot.
I've exposed the wall plate in two more locations, 1m and 2m to the left of the rot centre and the plate is 100% sound.
I've pulled a couple of the short ceiling joists out which means I can see right to the far end wall (0.5m to the right of the rot) and although the plate is knackered there, surprisingly the roof rafter seems mostly fine.
No hairy stuff anywhere.
Reckon I can cut, remove and slide a new plate in, if I lift the roof 1/2" with acrow props. I'll leave it open for now - it's no longer an urgent job. Let it get baked out a bit in summer then do it.
It can conduct water, but dry rot has no ability to wet up dry timber. Dry rot cannot attack dry timber. The same as every other brown rot.
It was not named 'dry rot' because it attacks dry timber.
Do you want to back that up at all? Because it dies when surface sprayed with boron, propaconazole, Jeyes fluid....It was never particularly tollerant of CCA pre-treatments either. Trametes versicolor, perhaps, but not Serpula lacrymans.
Matt
-I particularly liked the comment further up about it growing readily outdoors- so readily that a expedition had to be mounted to the Himalyas to find it! There are still only about five recorded instances of outdoor growth in the world.
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