Damp wall - good case for injection?

[Grunff]

Got that. Thanks for the advice.

[Mark]

See reply to Grunff I have used it on party walls, I also like the fact that you don't need to drill a bottom course of bricks full of 10mm holes, old Victorian bricks that have been damp for a number of years sometimes disintegrate when drilling the second hole. injecting into the mortar allows you to easily make good any small damage. Ask me again in 15 years if it is as good as the liquid in brick method.

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[Rob Morley]

Depending on the topology and geology, how about a sump?

[Andrew Gabriel]

You really have to prove it is rising damp before doing this sort of treatment, or you can make it much worse. How far is it rising above ground level (not floor level)? Is the sub-floor area swimming in a water leak? What is the wall construction, e.g. cavity, in which case water could be entering it from the top and running into cavity rubble at he bottom. (House is a bit old for cavity, but some areas were just starting to use them around then.)

If you have floor joist ends and wall plate embedded in the wall, you have to do this below them, although chances are they will have already started rotting. Party walls usually don't as the floor joists usually run front to back, but you should check this.

Cement render with waterproofer additive will prevent mild levels of damp reaching a gypsom plaster finish coat. Lime plaster on the other hand will allow mild levels of damp to pass through it without coming to any harm (providing you use appropriate decorative finish which doesn't seal it).

[Peter Parry]

Yes, hence my early caveat "if you can do it". Unfortunately the past laying concrete and tarmac up to walls sometimes makes it impractical to achieve. It might be worth checking where rain runoff from the concrete and tarmac is going. It is common for houses of that age to be built effectively in a small depression as soil will have been moved from inside the foundations. If water is running between the surrounding surface and wall it can pool in the middle. There is also the potential issue of long lost leaking pipes or leaking runoff water drains as others have said.

The trench doesn't need to be continuous - if you can cut any drainage ditches around the house it will reduce the problem. In the meantime as others have suggested you really need to look under the floor to determine what the problem is before going further. To do this without taking up the floor it is possible to hire endoscopes (I'm sure I've also seen one quite cheaply in one of the common tool catalogues recently) which would mean you only need to drill about a

1" diameter hole. I've also used a home made one constructed from a small 2.4GHz CCTV camera (USB one would also work) and a simple light guide from bent perspex but that required a slightly larger hole - about 1.5".

Unless you understand the cause of the damp it is unlikely any solution is going to work other than by luck.

[Grunff]

Ok, many thanks - that's given me lots to think about. Next time I'm over there, I'll do some investigation. I have a tiny USB camera which would be perfect for this.

[Stuart Noble]

A water leak would probably be localised, so that doesn't sound likely. Condensation highly unlikely if normal levels of heating and ventilation are maintained. I don't see any alternative to injection, although I wouldn't do anything without taking a good look under the floor. If the bricks below the damp course are porous enough to allow water through, somehow you have to reduce that. There's no doubt the treatment works if it's done properly which, in this case, means d-i-y. I don't trust contractors to use enough fluid

[Grunff]

I've no idea, since we haven't accessed the under floor void yet (if indeed there is one - the floor feels distinctly solid under the laminate).

Ah, but - some of the internal partition walls (single thickness brick) are also damp.

Right, I get the message - "must look under floor".

Ok, thanks for your advice.

[The Natural Philosopher]

Had just the same in my old cottage.

They had injected the external walls, and it worked, but the internal walls had not been done ..the large chimney area was uninjectable and this was the worst place.

[Phil Addison]

A low voltage (e.g.car) light-bulb soldered to some stiff wire would be easier? Or a high intensity LED head-band lamp fixed to stiff wire.

Phil

[Phil Addison]

*IF* it is a solid floor, doesn't this imply the slab itself is wet?

Whether or not you manage to inject a DPC below any wall-plate, I would try to slide a layer of modern DPC membrane under the plate anywhere there is the slightest sign of damp. The much maligned damp-meters can be of some help, though they do sometimes give a positive on perfectly dry material.

You can use a couple of hydraulic car-jacks under either end of a stout beam to take the load off 3 or 4 joists at a time - if there is enough clearance.

Phil

[Andrew Gabriel]

Chimney areas are often bad. They weren't well protected against rising damp, because they were warm or hot much of the time, and that made it unnecessary.

[The Natural Philosopher]

If the floor was laid with a DPM - and its not unusual to do this if a wooden floor rots out..then the damp simply transfers up the wall.

[DaveWu]

So you don't need to be an expert to talk bollocks

dave

[Mark]

I was simply saying what I have used in the same situation and let the OP make their mind up as to the merits of the advice. Fwiw my own house is part stone built and I have a French drain on the outside, the inside is lime plastered and this works fine for removing excess water from the footings and is entirely suited for this type of house. Neither of the above are suitable for the _interior_ party wall on a Victorian terraced house, a French drain is totally impractical and lime plaster although effective, most people seem to decorate this type of house with vinyl paint/wallpaper which would make it very ineffective. Hence why I have used and suggested a Cem-DPM. Perhaps you would like to share your particular prejudice, or are you from the- no such thing as rising damp party.

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[Stuart Noble]

Prejudice is particularly prevalent on the subject of damp for some reason. This particular case would seem to prove that rising damp does exist since there appears to be no other source. I might join the "no such thing as condensation" party though

[The Natural Philosopher]

I've had rising damp, penetrating damp and condensation. They all exist.

[Stuart Noble]

But I'd say condensation is unusual in centrally heated homes, other than the obvious cold surfaces. Hardly ever the cause of damp on plaster IME

[Peter Parry]

It is a very common cause of damp plaster in centrally heated homes. Most commonly council flats where the basic build quality is poor leading to cold corners in rooms combined with retrofitted double glazing and washing being dried on radiators.

It's common in many houses (but especially bungalows) where the cavity wall is not insulated and built in wardrobes are put on east facing walls. The inside of the wardrobe can soon become an interesting experiment in accelerated evolution.

[Stuart Noble]

And coal being kept in the bath