Rising damp, advice please

[MusicMan]

So this is in my house rather than workshop (ok a part of the house is a workshop!) but couldn't see where else to ask you experienced builders/architects if you can advise me on due diligence.

Had a cold call from House Guard, offering a damp survey to see if my insulation (blown rockwool) was allowing damp through, so thought no harm in getting their report. The guy came, equipped with a two-point moisture meter, rather the sort of thing one uses for wood. I saw him do the measurements so there was no sleight of hand. The readings on the old part of the house, about 60 years old, were: 30% in skirting boards, 15% on walls immediately over, dropping to 8% 50-60 cm above, dropping to negligible at 150 cm. The 20-year old part of the house (a big extension) showed no damp problems.

Conclusion was that there was no problem with the rockwool insulation, but that the 1960s-era bitumen damp-proof course was failing and needed replacing. This seems reasonable to me, is this right?

Of course they want to do the work. The walls are brick, with 1 or 2 courses visible before the DPC, this was bitumen covered originally but this has cracked and the mortar needs pointing.Above this the whole house is stucco covered, which needs some attention but is generally fairly good condition. The process would be drilling holes in the mortar, injecting the product "secoMUR", repointing brickwork all round then using black secoMUR to seal and replace the bitumen up to the start of the stucco.

The perimeter needing treatment is 30 m. and the price quoted is £3000. It would be about 2 days work for the team (no idea how big the team is).

My questions are

1. Does the diagnosis seem correct?
2. Is this the appropriate treatment for replacing a DPC in an existing building?
3. Is the price quoted about ballpark, cheap or expensive?

I'd be very grateful for guidance, comments and cautions.

Keith

 

[Sheffield Tony]

I am neither an architect or builder, but IMHO if a cold caller finds £3k of work on your house to fix a problem you previously didn't know you had, I would be skeptical.

I have heard it argued that rising damp is in the same category as woodworm; quite uncommon for it to be a problem. Before any injected treatments, check the ground levels relative to the DPC are 2 bricks or more, and that all gutters are clear and not leaking/overflowing, no pointing required on the brickwork, render still firmly attached, and that the damp meter is not just detecting condensation etc.

 

[That would work]

I too would be highly sceptical. I am not an architect either nor am I a surveyor. I do have a pretty good knowledge of how damp can permeate though. I've been frustrated by 'damp surveys' in the past whilst buying and selling properties. It's always felt like damp companies have a money printing licence when they can report negatively to a mortgage provider thus gaining work. I suspect that many older properties could provide high readings on a meter but I don't think that always means that there is a serious problem especially if timbers are not being directly affected. I know there are people on here who are better qualified to comment but I'm with the previous poster.....an out of the blue survey with a big bill? Mmm

 

[morturn]

I am a retired builder, and, in my opinion, I have never seen a genuine case of rising damp. I am not alone holding this experience either. The myth of rising damp as been a massive license to print money.

Over the years, I have watched these so-called damp expert cowboys relieve the unsuspecting public of millions of £ of their hard-earned cash.

Two-point moisture meters are not the way you measure the water content of brick and plaster. So, is your 1960s-era bitumen damp-proof course showing signs of damp? Or are you just going by that this guy had told you.

I have a house with no damp course, and that’s not showing any signed of damp.

Go and check for yourself the obvious signs, gutters, downpipes and for soil above the DPC. Check all air vents are clear too.

This guy talks a lot of sense: https://www.youtube.com/channel/UC55-NfrPh-SAT3wgwUFtruw

 

[sammy.se]

Hi,

Please don't spend any money yet - and these damp 'professionals' will often overcharge for solutions that don't even address the root cause of the problems.

Please see my own damp woes here: damp-in-victorian-house-dining-room-help-needed-t116193.html

Lots of great advice from the generous members of this forum (esp Mike G).

Please have a read through and perhaps you can tell us what kind of services you have near the damp? e.g. internal pipes, external gutters etc.

I also learned a huge amount from the Peter Ward videos on YouTube - the link posted above. I'd also recommend you go through those.

 

[MusicMan]

Thanks for the replies. I don't need the scepticism though, it was my natural scepticism that brought me to ask advice here.

The gutters and downpipes were renewed 2 years ago and are in good condition. No earth is piled up round the house. The mortar and pointing is definitely crumbling. There is no sign of damp or mould inside the house.

If not with a two-point meter, how would one measure damp in brick/plaster?

And does anyone have specific experience/knowledge about secoMUR or the company?

Added in edit: I should remark that the house is built on a concrete raft. There are no joists on the ground floor. Nor do any services at all come in on that side of the house. The one downpipe on that side, renewed a few years ago, leads to a soakaway in the garden, which I keep clear of soil and plants. (previous to the renewal, they had grown up the downpipe and blocked it!).

Keith

 

[MikeG.]

Damp is a complex subject, and I have only skim-read the thread. The thing that jumped out at me, though, was the bitumen on the plinth. Bricks work by holding moisture when it is damp, then releasing it when the air is drier. Putting bitumen or any other moisture barrier on the outside of a wall is a recipe for problems. I suggest that removing this would be a good place to start.

Further, the relationship of the floor level to the finished ground level externally is important, as is the detail of DPM and DPC. Most of the problems I come across are as a result of a hybrid of old and new construction techniques. A proper old house with lime mortar, lime render, good ventilation, and so on, can be perfectly dry without a DPC or DPM.........but as soon as you add one you cause issues. New extensions alongside old houses, with ill-thought through junctions, are also a classic. There is far too little information here to be able to give any sort of useful answer, other than don't let anyone do any chemical damp injection, or any plaster-stripping/ re-plastering. This is vandalism on a grand scale, and utterly ineffective over the long term.

 

[Jacob]

Are there any indications of a damp problem on the inside? If not then stop worrying.

 

[Rorschach]

Have you seen any damp in the house? If not, where is the problem?

 

[Marineboy]

There are a number of pieces of research which fail to find any evidence that rising damp is an actual phenomenon. The rising damp industry has made billions from scaring householders with this myth.

 

[Fitzroy]

I had a Victorian house in London that when I bought the surveyor had same such muppets in and they said ‘ooooh nasty one this, cough, rip all the plaster off inject plastic crap and replaster with waterproof plaster.

I read around the subject and decided it was a scam and would seal any penetrating water in and destroy the wall. There was visual no evidence of any problem. Then a few years later I noticed a patch of damp wall that was visually different and cold to the touch, I found a slow dripping (1 drip per 10 secomds) overflow from a toilet that had saturated the wall and slowly penetrated back. It was so obvious when there was actually a damp problem compared to the cowboy sticking the wood moisture meter in the wall.

When I sold, one potential buyer had a similar survey and came back wanting £5k of the asking price so they could get it sorted. I said no and ended up in a massive barny with the lady as I tried to explain that if they did the works they would be vandalising a 125yr old property and actually causing a problem. They wouldn’t listen and walked away, ho him their loss. Finally sold it to someone else who understood old houses.

Fitz.

 

[Sheffield Tony]

Actually, as well as the useful technical discussion, there's a simpler logic - never respond to cold callers. Good tradesmen selling a useful service don't have to cold call.

 

[Jonathan S]

Don't buy into the fear that these damp proofing companies sell, in my experience they know nothing about building practices, they know lots about how to part with people's money and are in cahoots with the banks.

One of my clients had to have a survey as there was a mortgage involved....there was no signs of damp.....we where with the surveyor as he went around the property and as expected from him he was finding damp everywhere.....when he put his meter down I got him talking and one of the guys got to try his meter.....they stuck it into the top edge of a door and low and behold the meter gave a high reading.

Do your own research, buy a meter and do your own tests.

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[Woody2Shoes]

The red flag for me was reading that you'd received a "...cold call..." - nuff said!

I'd echo what most of the others above say:
- There's probably no such thing as rising damp (in walls);
- Unless there's a problem (you can nearly always smell problem dampness) then don't try and fix it;
- Damp inside is often caused by condensation (exacerbated by trying to combine modern building materials and techniques with old ones) - warm damp air from a kitchen or bathroom circulating round the house until it finds a cool part (nearly always the bottom, which is often up to 5C cooler than the top) of a cool wall surface (usually a less well insulated one) - good ventilation is usually a major part of any solution;
- I have a house which is well over a century old with a perfectly intact bitumen DPC. Your DPC is extremely unlikely to be a serious part of any problem. Any damp getting into the wall from the outside will most likely be down to poor detailing (design of drips, eaves etc.) or new inappropriate paints/cladding trapping moisture or simply guttering/downpipes not functioning properly.

Unless you have an actual demonstrable problem (and a meter is not demonstrating anything IMHO) I'd do nothing. Even if you have a problem I would not trust these people to correctly identify/solve it!

Cheersd, W2S

 

[Rich C]

If not with a two-point meter, how would one measure damp in brick/plaster?

There aren't any good ways to do it non-destructively. Moisture meters are designed for unpainted wood and work well in that context, they're not worth using for brick or cement. The main issue is salt content in the bricks (absorbed from ground and rain water) which throw off the correlation of conductivity of the brickwork to moisture levels. So you can have two bricks with identical moisture read very differently dependent on salt content. Also, due to gravity and ground contact you're likely to get more salts lower down, hence the readings seen - this just happens to tie in nicely with "rising damp".

As for the skirting, it could easily be bone dry but painted with lead paint if it's 60 years old. Lead paint will register as a huge amount of moisture as it effectively shorts the meter. You'd need to test a bare piece of skirting to get a correct reading.

Rising damp is a real thing, but it's very rare in practice. The majority of damp in houses is condensation due to poor ventilation (especially older houses retrofitted with double glazing). The rest is generally pentrating damp from a gutters, poor brickwork, etc. or a leak somewhere.

 

[Phil Pascoe]

A friend some forty years ago had a problem with "rising damp". He parted with a lot of money having a chemical dpc put in one summer - great, he though, problem solved. Until the water started running in through the wall above the dpc - it was coming through rendering defects much higher up the outside of the wall and tracking down through. The dpc had stopped it going to ground.

 

[Jonathan S]

Another Dampey story.

A client asked if I could take up her engineered teak floor up, when I asked her why, she tells me they have rotting skirting boards and there builder tells her they have a leak in there underfloor heating and it all has to come up and be replaced
My natural investigative mind asks her if she been adding any water to the underfloor heating, she hadn't....so I got her to hold with ripping her floors up and find what was really happening. We investigated all the usual plumbing and duct work and found nothing.
Scratching my bald head I asked a friend/ builder to help....he came to site and spent some time investigating, his verdict was the Spanish tiled roof is the source and needs repointing.....the clients didn't belive it, but I got them to trust the information and they eventually arranged to have their roof repaired.....solved the problem!....the water was coming in via the roof, travelling along a concrete ceiling down a wall and into the floor, it showed no evidence of any damp until it was in the floor......


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[novocaine]

the only true way to test for damp in plaster and brick is to drill out a sample then use a calcium carbide chamber. basically when moisture comes in to contact with CC it reacts and produced acetylene gas, the pressure of which can be monitored and correlates to the amount of moisture in the sample.

the muppet with his resistance probe isn't doing you any favours by using it, as already alluded to above there are many things that can result in low residence and have nothing to do with moisture.

if you now have a concern, contact 3 other companies (preferable one of which should be a building surveyor) and get a range of opinions.

cavity wall insulation extraction is the new cavity wall insulation installation which was the new DPC injection. mostly a con that can result in no end of problems for the property and normally installed by a bunch of cowboys who have no regard for the property, it's construction or it's environment. (having just been stung for 2k to have it removed because of the PO who got a grant to do it, on a property with pourous warrington brick from the 1940s and a gable end that's exposed to driving rain with a painted finish, I rather dislike the whole damn industry)

 

[Jacob]

I know not everybody agrees but I think rising damp is a bit of a myth - it's more a case of falling damp descending through a structure until it meets a saturated level usually about ground level, at which point it backs up a bit and can stay higher than ground level.
PS though having now read this https://en.wikipedia.org/wiki/Damp_(structural)#Rising_damp maybe I'm wrong, but it's not as common as folk like to think.

 

[MusicMan]

Thanks to everyone for their advice, which is very helpful. To answer questions: there is no trace of damp inside the house by mould, smell or feel. My original concern was following press reports that blown rockwool cavity insulation could develop tracking paths for moisture over time (it was done about 25 years ago). There was no trace of this even from the representative of the firm that contacted me. He claimed that the higher readings of damp low down were indicative of rising damp, hence my due diligence on this forum. The two-point probe readings he took are the only "evidence" of this.

Following advice here, I have gone over the house more carefully and thoroughly, using my own wood moisture meter, which is a pinless type, in principle sampling a larger volume. There is a problem calibrating all moisture meters in absolute terms, so I only did comparative measurements. Fortunately I had skirting boards of the same wood both on external walls and on internal ones, both unpainted. I could not find any systematic difference between the two.

The pinless type probably also gives a better reading on walls than the pin type, though calibration is very uncertain. However, I could not find any systematic variation with height on the walls either.

I conclude (along with the great majority of repliers here) that the firm trains its staff to use inappropriate meters, which are likely to give false positives.

The most that might be worth doing is repointing the brickwork below the render (looking at MikeG's comments). Looking at it now, the bricks are probably not covered by bitumen, but by a relatively thin black paint - hard to tell. I attach some pics of the brickwork. For the last one I dug down a bit to remove soil (which is sandy and quick draining). I must admit I cannot tell where the DPC occurs! Anyway, comments on these will be welcome.