The refurb of the flat is continuing with the eradication of the dry rot, the completion of the first-fix (before the plastering) electrics, and the building of false ceilings beneath the existing, to provide sound-proofing.
I use an unorthodox method to deal with dry rot, and link to my blog. The conventional method is to chop out the affected wood at lease a metre beyond visible infection, then saturate everything in chemicals. I used to do it this way, but there are problems in that the chemicals are very toxic and can be harmful to people. Also they don’t soak all the way into the wood, and dry-rot can be extremely persistent and make its way along the untreated core of the wood, avoiding the chemicals on the outside.
rotten window sill and dry rot hyphae beneath
My method relies on the simple fact that all living organisms need water to survive. Dry Rot is a misnomer in that it needs to have its feet in water somewhere and requires conditions of quite high humidity to survive. But it is able to transport water from one place (such as a basement) over very long distances (such as to a roof). All I do is look for the source of the moisture and eliminate it. In this case it was a leak under the bath, and a soggy window sill below the rotten windows. The infection is now dead.
I’m not suggesting others try it, and I’m not sure if you can get guarantees with this kind of work. Until such guarantees can be obtained most people will unfortunately have to rely on the conventional chemical method.
There is a lot of information on the internet about dry rot, and probably even more misinformation. I’ve been told variously that it can move water up to 30 metres from its original source, or that it can’t move water at all. That it can go through solid concrete, or that it can only get thru fissures in loose mortar. That it can destroy a whole building and neighbouring buildings from within, or that it can’t. That it can be killed by cutting off it’s water source, or that it can’t. LOADS of contradictory information. So, in this blog I won’t rely on any of these sources, but will just tell you what I have seen with my own eyes.
First off I’m a carpenter and builder, not a dry rot specialist. If you have issues with (for instance) a cartilage injury in your knee, you’d get a referral from a GP to an orthopaedic specialist. I’m like the GP. Although I know the signs of dry rot, I certainly don’t know everything there is to know about it. If I suspect dry rot, unless it’s fairly minor and easy to contain, I’ll refer it to a specialist.
The risk for most people is that they get mis-sold a lot of unnecessary, costly and toxic chemical treatments. Sometimes the simple removal of the infected timber and isolation of the new timber from any water sources would be enough. As a builder it’s much harder for anyone to pull the wool over my eyes, but a private customer needs to beware of this, get three different quotes and ask each about the alternatives. You also want a 30 year insurance-backed guarantee.
Having said that, I have eradicated it by simply removing all the visibly affected wood, and cutting back a further metre beyond that. The wood was burnt. Any fruiting bodies (more on them later) were removed carefully and burnt to avoid re-infection. Hyphae were destroyed with a dilute brick acid mix. This is hydrochloric acid, which is dangerous as it can burn, but not toxic. Then all potential sources of moisture were removed or sealed up to dry the building out and prevent any moisture getting back into the wood. Damp Proof Membranes were placed under timbers which were resting on damp masonry.
The Lacrymans latin name for Dry Rot may relate to the English word ‘lachrymose’ meaning to cry excessively. Dry rot spreads a ‘mycelium’ (fungus root formation) of ‘hyphae’ (fungus roots) often covered with water droplets, like tears. It can cover a wide area including walls, concrete floors and other surfaces which you would think would offer it no succor. It looks a bit like a very course spider’s web in the morning dew.
dry rot destroying floor
It will also have a fruiting body or fruiting bodies somewhere. These look like flattened, white (when unripe) to rust-brown patches sticking to a suitable surface, and could be just an inch or so diameter to 18 inches or more. They release millions of rust-coloured spores and a fungal smell.
fruiting body
I have never seen the fungus grow in dry conditions such as in the open in a reasonably dry room. I have seen it grow openly in damp rooms. It appears to need high humidity for the mycelium. This would explain how it creeps secretly throughout a building, under floors, behind skirting boards, through damp walls and cavities. A damp-loving, dry-hating habit which means it doesn’t show itself on the surface of the wood until it has rotted out the heart and all the hidden parts of the building. The fruiting bodies tend to appear in more open, drier spaces, so that spores can be wind-distributed.
note the drier skirting is hardly affected, while the floor below is destroyed
In the third pic you can see how it has destroyed the floor under the lino, which would have kept the dampness in, while it has only just started to show as a crinkling on the dry surface of the skirting.
surface crinkling
The first indication may be a floor dropping below the skirting, although wet rot can also cause this. Or a slight crinkling of the surface of the wood. Then the wood shrinks more and cracks along the grain appear. Then cracks across the grain appear too, leading to the classic cuboidal cracking.
BUT – many other types of fungus can also lead to these signs. If in doubt, get it checked out.
I wrote about ceilings last week, this week I’m assessing internal walls, so take a long spirit level to gauge how flat, plumb and level the walls are. Doorways with unlevel heads may indicate settlement or subsidence. Another common indicator is wallpaper with diagonal creases where two walls meet. This can happen with any type of wall construction, and indicates that one wall has moved down relative to the other since they were papered. There will probably be diagonal cracks in the plaster underneath too. This isn’t necessarily a major problem in older, pre-building-regs houses with shallow foundations but which have stood the test of time. Particularly if the paper has been on for decades and hasn’t moved much. If unsure, get an engineer’s report. As I said in my blog about surveyors, for specific concerns an engineer is better than a surveyor’s report, as an engineer doesn’t just trouble-shoot but can suggest solutions as well.
As with ceilings, timber-framed internal walls come in two main types (plasterboard and lath-and-plaster). Walls may also be single-skin brickwork which I’ll cover next week.
Lath-and-plaster walls on a timber frame are subject to the same problems as ceilings which I discussed last week, except without the danger of concussing occupants by falling on their heads! They are easily damaged by impacts, the thin wooden laths flex on the frame, causing plaster to crack and fall away. Try pressing any indented bits with your fingers. If it moves easily it needs to come off and be replaced, either with a plasterboard patch or if more than about 10% of the total area then the whole wall. It’s not a big job, but skirting boards and architraves may have to come off, so get quotes. If lath and plaster walls are in good condition and bare of paper and paint, but just a bit rough, they can be revived with a quick skim of plaster (surprisingly, quicker, cheaper and better than lining paper).
cuboidal cracking
In many older houses timber-frame walls were built straight onto stone or concrete floors with no damp-proof-membrane (DPM) and eventually become riddled with rot and woodworm. If suspect, try the key test – pushing a long key (or screwdriver) into the bottom of any wood showing. If it yields easily, it’s rotten. If it shows signs of cuboidal cracking, it may have dry rot. The solution to the damp is to remove it all and replace on a plastic DPM to stop the damp. Dry rot is a bit more involved.
Little known fact – woodworm is also associated with damp. If you install central heating and reduce the relative humidity in the house enough, woodworm will die too. All creatures need moisture and if you deprive them of it completely they can’t survive. That’s why they congregate where timbers are damp.
As with ceilings, plasterboard walls should present fewer problems, so long as there are enough fixings and it’s dry.
Second little-known fact – timber walls can be load-bearing. Many times I’ve used a 4” x 2” timber frame wall to carry the floor above for a loft-conversion, to the complete satisfaction of the Building Inspector. If planning to remodel the house, don’t assume you’ll be able to pull out timber walls without putting in some kind of support for floors and walls above!
