Rising damp - really?

[Penners]

the assessor was whingeing about not knowing what the existing level of damp was before the flood. Duh! He reckons that because they can't ascertain what it was before, they can't pay out because they don't know how much damage has been done by the flood.

That's outrageous! If a roof blows off in a storm, do they refuse to pay for its reinstatement because they didn't have details of its condition beforehand? If someone drives into the back of your car, do the insurers refuse to pay for its repair because they don't know whether the rear bumper was scratched beforehand?

If the floor was carpeted before the flood, then clearly it was dry enough to be carpeted. So surely the insurers need to restore it to that state of dryness and repair.

If they continue to try to dodge payment, I suggest you tell them that you will initiate a complaint procedure. See: https://www.moneyadviceservice.org.uk/en/articles/making-a-complaint-about-an-insurance-company

Just for the benefit of other forum users, which insurance company is this?

 

[Gareth Hughes]

It's partly based on my own observation and conversations with heritage professionals in the Netherlands. And it's partly based on the same conclusions reached by Jeff Howell, whose 'The Rising Damp Myth' I would recommend.

 

[Lindyboo]

Just for the benefit of other forum users, which insurance company is this?

Halifax's own insurance (we are in thrall to them). They use Polygon for the drying (it's they who've said that they doubt any paying out will be done) and the decision will be taken by a bod from Gelders after consultation with their own builder. Gelder's assessor was initially happy to replace as required, but the lack of drying out has led to the potential conflict. They arrive en masse on Thursday to review and bestow blessings - or otherwise.

 

[Gareth Hughes]

Well I think it does exist, the only reason being that I had damp walls here - it's 9" solid walls with very soft porous brick; the damp would come up to about 300-400mm or so every time we had a spell of wet weather, and fitting a proper impermeable damp proof course fixed it completely.
That's not to say of course, that every diagnosis of rising damp is correct.

it came up a foot or so in wet weather. And then it went away again? And what are the ground levels and surface finishes outside?

 

[Penners]

They arrive en masse on Thursday to review and bestow blessings - or otherwise.

Do let us know the outcome, please.

 

[88v8]

When you bought the house, you had a survey? And so did Halifax?
And they said what about damp?

How long ago were you flooded?

Ivor

 

[Penners]

When you bought the house, you had a survey? And so did Halifax?
And they said what about damp?

Very good point, Ivor.

 

[Lindyboo]

Damp was not mentioned on the survey, to the best of my recollection. Such damp as we've been aware of we've lived with and, apart from one section of porous wall in a vestibule, it hasn't caused any great inconvenience.

We were flooded when Hurricane Bertha came over - about 3 or 4 weeks ago must have been.

 

[Penners]

In which case, Ivor has given you a very effective argument against the suggestion that there was damp before the flood. If there was, the building society's survey would have identified it.

I shouldn't mention " Such damp as we've been aware of we've lived with and, apart from one section of porous wall in a vestibule, it hasn't caused any great inconvenience". Clearly the building society surveyor didn't see it as an issue.

 

[Lindyboo]

In which case, Ivor has given you a very effective argument against the suggestion that there was damp before the flood. If there was, the building society's survey would have identified it.

I shouldn't mention " Such damp as we've been aware of we've lived with and, apart from one section of porous wall in a vestibule, it hasn't caused any great inconvenience". Clearly the building society surveyor didn't see it as an issue.

Good point.

 

[Flyfisher]

Yes, very good point Ivor.

An independent professional report confirming no damp problem must surely carry more weight than a retrospective guess after a flooding event. If the world has not gone completely mad anyway.

 

[Matt Green]

Time to look at the problem in a slightly different way:

Flood water is fresh rainwater that has moved directly into the building, whereas moving up the base of the walls has moved through soil, picking up hygroscopic salts along the way. There is a very easy way of telling them apart that involves a hammer drill, an oven and salt chamber. Essentially, you need to know the salt content of the wall to determine a) the presence and b) the likely source of any water. Both water and ground water salts are electrically conductive, so a resistance meter is not going give a definitive answer you need a more invasive test that involves removing samples of masonry (collecting the drill cast-offs from boring a hole). Once you have a sample of wet masonry:
- weigh it (wet weight)
- dry it in an oven at 50C for 24 hours
- weigh it (dry weight) (difference is the free water content)
- leave the sample in a salt chamber and see how much they reabsorb (which gives the portion of the free water absorbed by salts in the sample)

Take samples at 250/500mm interval in a line up the wall to see change with height.

When ground water moves up through the base of a plastered wall due to capillary action*, when it gets to about 1m the upward pull becomes equal to the evaporative pull into the room, so a band a salt forms in the plaster and masonry at that height where the salts are left behind. Say you do what I outlined above:

Height from floor (m):
0.25, 0.50, 0.75, 1.0, 1.5

Flood water still in the wall and evaporating out slowly would give you high free water readings up to about 0.5m
Ground water moving up through the base of the wall would give high free water reading at 0.25 and 0.5m and a high hygoscopic readings at 1.0m


Matt



*This process is referred to by some as rising damp and by others as capillary action; no one disputes the effect, but there is a lot of disagreement about the cause. The rough positions on this are:

Remedial industry position:
Rising damp IS capillary action- they are one and the same thing, so therefore rising damp exists.

Building preservation specialists:
Capillary action exists, but if the building functions as intended it never 'spontaneously occurs'. It is an effect, not a cause. Find the cause and remove it, then the effect will never trouble you and the building will never require a DPC.

Academics with tenuous grasp of the real world position:
"We put some un-plastered brick piers in a tub of water and nothing happened"

 

[TheRoost]

I learned about the myth of rising damp a while back here -

http://www.heritage-house.org/managing-damp-in-old-buildings.html


http://www.heritage-house.org/rubbish-taken-from-the-damp-companies-websites-.html


I have also read somewhere else, that in Holland they build house footings in 3 feet of standing water, no DPC, no issues. Construction students over there laugh at our 'Twee English custom' of installing 'damp proof' courses.

In principle, as I understand it, any moisture in a old brick wall drawn from the ground should evaporate from the brickwork/mortar at the first course above ground, and not travel any further up. Add in waterproof cement render, cement pointing, modern plaster, poor ventilation etc, and the moisture has no way of escaping normally, and remains in the wall.

The 1890-ish brick built house we bought recently doesn't appear to have a course of 'blue brick' at ground level which I think is what late Victorian builders used a dpc(?) the course of bricks below ground level are quite wet (poor drainage I think) but the course above are bone dry visually and to the touch.

 

[Zebra]

Well I think it does exist, the only reason being that I had damp walls here - it's 9" solid walls with very soft porous brick; the damp would come up to about 300-400mm or so every time we had a spell of wet weather, and fitting a proper impermeable damp proof course fixed it completely.
That's not to say of course, that every diagnosis of rising damp is correct.

Sounds like ours - 9" brick, soft, porous. Is it visible damp or do you use a meter? I'm considering buying one, if affordable. What sort of damp proof course did you install?

I didn't use a meter, I could just see the damp. I'm' afraid I'm a bit busy (lazy!), and shall refer you here:
https://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=13077

 

[Ebenezer]

Well I think it does exist, the only reason being that I had damp walls here - it's 9" solid walls with very soft porous brick; the damp would come up to about 300-400mm or so every time we had a spell of wet weather, and fitting a proper impermeable damp proof course fixed it completely.
That's not to say of course, that every diagnosis of rising damp is correct.

Sounds like ours - 9" brick, soft, porous. Is it visible damp or do you use a meter? I'm considering buying one, if affordable. What sort of damp proof course did you install?

I didn't use a meter, I could just see the damp. I'm' afraid I'm a bit busy (lazy!), and shall refer you here:
https://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=13077

Wow amazing work there zebra, how are your walls now?

 

[Zebra]

Dry. Absolutely fine.

 

[88v8]

Time to look at the problem in a slightly different way:

This analysis could indeed shed light on the pre-flood condition. The practicality perhaps founders on the quantum of the disputed claim relative to the cost of Lindy having the analysis carried out. Alas, the insurers are unlikely to volunteer their services.

However, if Lindy were to say that she will if necessary have this investigation done but the cost will be added to the claim, that would be a negotiating point in her favour. The mere fact that she knows how to analyse the origin of the damage, will be impressive.

Sadly the insurance industry has rarely been good at paying claims. Deny, dispute, delay, dissimulate, diminish... the name of the game.

Ivor

 

[Penners]

if Lindy were to say that she will if necessary have this investigation done but the cost will be added to the claim, that would be a negotiating point in her favour. The mere fact that she knows how to analyse the origin of the damage, will be impressive.

...except that this approach carries the risk that, in the event of the claim being finally rejected, Lindy will have the investigation cost to pay for, as well as the reinstatement.

 

[plasticpigeon]

It is a shame to rubbish experiments performed under controlled conditions as academic irrelevance. That kind of experiment can aid understanding. For example, it is not sensible to deny the effect of capillary action, but if under controlled conditions water rises a certain distance up the wall, then it seems very likely that significant moisture above that level is caused by something else. Also I have no knowledge of the mechanism that causes capillary action, but it is definitely to do with pore size, surface tension and density of the fluid involved. It should be possible to find a representative figure for pore size of a brick, do a calculation and get a reasonable estimate for the height that this effect can cause water to be drawn up a wall. I have never seen any calculation like this, but have seen endless online discussions. Has anyone got any references for this type of approach or calculation. Also what effect do the mortar joints have? How is capillary action effected by the interface between materials with different porosities.

 

[Penners]

I have no knowledge of the mechanism that causes capillary action, but it is definitely to do with pore size, surface tension and density of the fluid involved.

I agree, PP, but I reckon that the interconnection of the pores is also a significant factor. "Closed cell" pores would not permit capillary action.