Dry Rot Surveyor?

[Timw]

I'm wondering if anyone has come across a good surveyor - preferably not too far from London - with specialist knowledge of dry rot?

We have a musty smell in the house, but no obvious signs of the cause. Before tearing up floorboards and dry linings, I'd like to have someone who knows about these things come and take a good sniff.

Tim

 

[monmaison2009]

My property suffered from some raising dump in the past, I have used Rentokil, they are professional and they guatanty their work. They do dry rot too, so they might be able to help

http://www.rentokil.co.uk/residential-customers/property-care/rot/index.html

 

[Gareth Hughes]

I'm wondering if anyone has come across a good surveyor - preferably not too far from London - with specialist knowledge of dry rot?

We have a musty smell in the house, but no obvious signs of the cause. Before tearing up floorboards and dry linings, I'd like to have someone who knows about these things come and take a good sniff.

Tim

The cause is damp, the symptom is dry rot (though a musty smell isn't necessarily a sign of dry rot - which smells, overpoweringly, of dried mushrooms). Moisture must be getting in from somewhere, or still be present (if the house has been dry lined, it's possible that this was done to cover up some of the evidence).
I assume you've gone through the usual checklist - roof, flashings, gutters, downpipes, vegetation, ground levels, render (if any), chimneys, lack of ventilation?
Don't call in the likes of Rentokill until you are sure that the cause as well as the symptoms have been understood.

 

[Moo]

Please do heed Gareth's wise words and remember that firms like Rentokil make their considerable profits by selling 'treatments'.
Their shareholders might object strongly if they were to turn away business by telling customers to follow Gareth's advice.

 

[Timw]

Thanks, the checklist does indeed remind me of some the things, such as the chimney, that I have not yet checked. And whilst the bouquet is musty, I don't detect dried mushrooms, so perhaps things may not be as serious as I thought.

But if anyone does know a surveyor with a good nose, do let me know.

 

[michael]

Someone may wish to correct me here but my understanding is that dry rot comes out of the ground i.e. it’s not airborne (except for the spores local to the growth) and therefore it tends to start at the bottom of a building and work its way upwards. If my analogy is correct, then I think it’s well worth lifting a few floorboards around the ground floor and getting your head down there with a torch checking on the underside of the joists for the thin flat web type tentacles and on the soil for rust coloured mushrooms or rust coloured dust (spores) which have exploded from the mushrooms.
Dry rot dose need moisture so I would tend to look in areas where moisture could be reaching your under floor timbers e.g. where floor joists meet walls etc. failing damp courses or wherever there is a path between the timber and the soil.
Musty smells often mean damp old timbers and perhaps a touch of ‘wet rot’ lurking under the floor and not necessarily dry rot. So in my humble opinion, have a good look under the floor first and then call the specialists if necessary. I think if you called them now they would simply do the same thing and charge you for it.
I used to experience a musty smell every time I entered the front door of my house. It turned out that the culprit was right below my feet. A rotten joist end, close to the front door, which is now repaired /replaced. Musty smell gone.

 

[Timw]

Thank you, Michael. I will certainly start lifting some boards and do as you suggest.

Tim

 

[Moo]

And don't, whatever you do, call in a damp specialist who offers 'free consultations'. Find the cause, sort it, and sit back smugly and count all the money you've saved.

 

[stuart45]

Dry rot usually starts under timber floors at ground level because the ideal conditions often exist here. Timber joists up against, or built into damp brickwork will normally start an attack off. It might be worth checking your air bricks as well. Floors with a serious problem are often spongy when jumped up and down on. BRE Digest 299 is worth reading.

 

[Matt Green]

Someone may wish to correct me here but my understanding is that dry rot comes out of the ground i.e. it’s not airborne (except for the spores local to the growth) and therefore it tends to start at the bottom of a building and work its way upwards.

No, there is no proof of that at all in anything I've ever seen or read.

Dry Rot follows areas of freshwater wetting, like water it falls through a building as water falls through a building. Dry rot needs moisture but spore germination is unlikely to occur is areas where there is groundwater ingress into the building fabric- there are too many dissolved salts in ground water. Dry rot is far more commonly seen after freshwater ingress, so check things like down pipes, pipework, drains, flashings etc.

If existing dry rot gets to ground level is can growth reasonably well in areas where ground water is an issue (and it can be a pain to get rid of once it gets to that point) but, usually, it doesn't start there.

Dry rot usually starts under timber floors at ground level because the ideal conditions often exist here. Timber joists up against, or built into damp brickwork will normally start an attack off. It might be worth checking your air bricks as well. Floors with a serious problem are often spongy when jumped up and down on. BRE Digest 299 is worth reading.

That's really not the case at all. It's ideal for some species of wet rot (a horrible term for 'everything that isn't dry rot) including, but limited to cellar rot and mine rot but not dry rot. Joist pockets with ground water penetration might have timber moisture contents in excess of the 28%ish needed for dry rot spore germination, but the dissolved ground salts are just not right for it's growth. Equally dry rot can never be caused by a lack of sub-floor ventilation under a pine floor- the timber moisture content can never get high enough for spore germination without another water source. BRE 299 is written very cagily and by people who may not be entirely objective, there are better sources to read. The Old House Handbook (Hunt & Suhr) is pretty good*, Timber Decay in Buildings (Ridout**) is technical but exact and Survey and Repair of Traditional Buildings (Oxley***) is expensive but shows the thought processes behind what is necessary to to undertake an accurate job.

There is a massive amount of downright wrong information about dry rot. find out some basic biological information about it. Work out what it can and can't possibly do then mentally check the high risk areas (downpipes, guttering, flashing, plumbing, drainage) and investigate them.

Matt

*slightly biased in recommending that one
**my old boss, so more bias there
***met him, nice bloke

 

[Lime]

I echo Matt Green in what he says, the facts do not live up to the reputation that dry rot has acquired over the years.
Unsupported accounts of dry rot make excellent horror stories but I have never experienced it like that.
I've seen it in damp/dry roof spaces and it can be quite alarming to discover it because it may grow big like a plant.
However as soon as the leaks are stopped it withers away.

There is a lot of money to be made "treating" the dry rot myth and the treatment companies like it that way.

 

[stuart45]

Dry rot usually starts under timber floors at ground level because the ideal conditions often exist here. Timber joists up against, or built into damp brickwork will normally start an attack off. It might be worth checking your air bricks as well. Floors with a serious problem are often spongy when jumped up and down on. BRE Digest 299 is worth reading.

That's really not the case at all. It's ideal for some species of wet rot (a horrible term for 'everything that isn't dry rot) including, but limited to cellar rot and mine rot but not dry rot. Joist pockets with ground water penetration might have timber moisture contents in excess of the 28%ish needed for dry rot spore germination, but the dissolved ground salts are just not right for it's growth. Equally dry rot can never be caused by a lack of sub-floor ventilation under a pine floor- the timber moisture content can never get high enough for spore germination without another water source. BRE 299 is written very cagily and by people who may not be entirely objective, there are better sources to read. The Old House Handbook (Hunt & Suhr) is pretty good*, Timber Decay in Buildings (Ridout**) is technical but exact and Survey and Repair of Traditional Buildings (Oxley***) is expensive but shows the thought processes behind what is necessary to to undertake an accurate job.

I have worked on a number of jobs over the years where dry rot has destroyed the ground floors, often starting on the wall plates on the sleeper walls. Certain of the wet rots are sometimes confused with dry rot, but most of these had samples tested. The majority of dry rot cases I have seen were in the ground floors, although not totally restricted to them. BRE have done extensive research in timber rot over the years, although I agree that 299 does contain some maybe type imformation.

 

[Matt Green]

I have worked on a number of jobs over the years where dry rot has destroyed the ground floors, often starting on the wall plates on the sleeper walls. Certain of the wet rots are sometimes confused with dry rot, but most of these had samples tested. The majority of dry rot cases I have seen were in the ground floors, although not totally restricted to them. BRE have done extensive research in timber rot over the years, although I agree that 299 does contain some maybe type imformation.

I find that difficult anecdotal evidence to swallow. I've seen a lot of dry rot. It's always had a source of fresh water and, overwhelmingly, the majority of cases arose around downpipes, guttering or other rainwater equipment. I can see that dry could develop under ground floors where there is a flood risk or rainwater drainage backs up through vents but I have never seen a causal link between ground water and dry rot.

Consider a range of properties for a moment from terraced houses to country mansions, all with timber floors. You would expect that instances of dry rot would be proportional across the range. It's not; big houses are more at risk from dry rot than small dwellings. I would be happy to bet the list of stately homes that haven't been affected by dry rot is very small indeed. The reason this particular fungus isn't running rampant across the country (cases aren't common given the number of houses, surveys and sales) is simply linked to roof area: the bigger the area, the more rainwater needs moving and the harder and more expensive it is to manage it's removal.

I'm aware of one study of survey information on dry rot outbreaks in the Architect's Journal from a while ago that backs this view up to a point (given the information was collected from remedial surveyors, who are not always objective about what they are apparently seeing). Finding, retrieving and obtaining data from the BRE is tantamount to impossible- the last time someone quoted a BRE survey of alleged 'rising damp' in properties I was genuinely intrigued and called them for more information. They denied all knowledge couldn't point me to any surveys of the kind, wouldn't let me talk to anyone that might know, didn't know where I should look and didn't seem to care. They are an outdated institution that seems to scrape by on money thrown at them from the PCA/BWPDA so they can "quote the BRE" to give the industry an impression of scientific rigour when there is very probably nothing to any rigour to show.

It's not that hard (usually) to identify active dry rot from the wet rots that have similar mycellial structures like Antrodia (Fibroporia) and some of the other Poroid types. It's more difficult to identify if it's dead but given the resolution of the damage should be exactly the same, whatever the species of fungus causing the brown rot decay, identification of the cause, rectifying it and repairing the effects are all that matter at that point.

 

[stuart45]

I havn't stated that groundwater was the source of moisture that caused the problem, but that the conditions for dry rot to develop were often found in old properties with suspended timber ground floors. Many of the houses I worked on with this problem were Victorian terraces, especially in the 70's and early 80's when old neglected rentals properties were being restored for the private market.
The lack of oversite concrete, poor ventilation, high ground levels and penetrating damp as well as defective gutters all added to the problem.
Nowadays the problem is more likely to be found in the larger homes, as many of the smaller ones have now been done. I would not have any idea of the proportion of smaller houses with this problem compared to larger ones however.
Any infected timber nowadays is burnt on site.
Damp brickwork is not normally caused by groundwater. It is usually caused by penetrating damp, condensation or leaking pipework. Timber resting against or built into this will tend to stay permanently damp.

 

[michael]

All very informative Matt/Stuart. I’m impressed with your knowledge but it still begs the question where does dry rot come from?
Options seem to be: The ground, the air or in fresh water.
The ground seems to have been ruled out due to the salts issue. If it’s travelling around in the air (the atmosphere) then I could understand how it finds its way into loft spaces and takes advantage of a fresh water supply (a rain water leak etc.) but how does it find its way to under floor areas which in a large number of cases is the first area of outbreak. I understand the conditions could be ideal for it, an ingress of rainwater under a timber floor but if it’s not generally lurking around on or in the ground, how does it find its way down there if as I say, the initial outbreak in many cases is under the floor. Is it washed from the air to ground level by the rain perhaps?

 

[stuart45]

Dry rot starts live as a tiny spore, which are around in the same way that mould spores travel around in the air. They can find their way into any part of the house, but will only germinate where the conditions are right for them. Where there has been a serious outbreak, a lot more spores will be around.

 

[Matt Green]

I havn't stated that groundwater was the source of moisture that caused the problem, but that the conditions for dry rot to develop were often found in old properties with suspended timber ground floors.

Well, that's true but you didn't state it until that post and if someone comes across this thread in the archives it's good to explicit if there is more than one potential source of moisture ingress. That reduces any potential panic and allows cooler minds to prevail, all of which is good for the house.

The point I'm trying to get across is that there is no need to immediately suspect dry rot in a ground floor void if there is no evidence to suggest that water is getting into it. The fact there is a suspended ground floor on it's own is not enough to cause dry rot. Neither will a lack of ventilation on it's own because the resulting high humidity and condensation on it own won't cause dry rot because the timber cannot physically get wet enough for spore germination to occur without another source of water, even at 100% RH. All of which is neither here nor there until impressionable folk start panicking and smacking holes in the walls of their period properties because a surveyor has noted that it doesn't have the requite number of airbricks to meet modern standards.

Penetrating damp (by your definition and that of PCA members) and specifically penetrating fresh water, or something like fire hoses, flooding or appliance failure is needed for a dry rot outbreak. Once that happens, then all the above become serious factors in keeping an outbreak going and it's likely to go unnoticed under a floor until the growth and damage becomes severe enough to notice.

All very informative Matt/Stuart. I’m impressed with your knowledge but it still begs the question where does dry rot come from?
Options seem to be: The ground, the air or in fresh water.

Microscopic airborne spores, as Stuart has said. They can get everywhere, certainly under floors or through vents. The mycelium (asexual growth stage) can remain moribund for a while in brick, which is why it need be sterilised before being used as hardcore- there are a couple of anecdotal reports of unsterilised hardcore causing dry rot. Same with timber which is why paranoid folks burn it despite the fact it's not going to be re-used. Not all soil is the same either, if there is a high content of timber for whatever reason (shavings, offcuts thrown under floors- that sort of thing) spores will germinate on them if it gets wet enough.

The long and short of it all, Michael, is that we reckon you should pop up a few floorboards

 

[Timw]

Clearly this is a complex (and controversial) subject. Thank you all for your wise contributions.
Tim