Damp Proofing 30 January at 9:37PM in In my home (includes DIY) MoneySaving 9 replies 369 views

Chucklechops

Hi

I'm about to have some damp proof work done to my house, and I've opted not to have the damp proofers replaster the walls after they've been treated, as I think the cost is prohibitive - I'll get my own plasterer to do that.

However, the damp proofing specialists recommend having a 'dry wall coating' applied. They state:

'To control rising dampness in a wall, in addition to the proposed damp proof course, it is of great importance that internal plaster is capable of preventing hygroscopic salts affecting the wall surface. Our recommendations and comments are as follows: - It is recommended that the walls to be treated are re-plastered to an even height as indicated on the sketch, strictly in accordance with our specification for ‘DryWall Coating’.

My question is, will any 'regular' plasterer be au fait with this term, and will they be able to apply the coating before they plaster the walls? Or is it a special type of plaster they should use?

Many thanks for any help.

 

FreeBear

Please, have a read of this web site before you let these "specialists" in - https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

If you have solid wall construction, a lime plaster would be better suited to the building than a gypsum one (e.g. Multifinish) or the waterproof render/plaster these guys usually slap on. At least the gypsum plasters have the advantage of being easier to remove when you find the chemical injections have failed to solve the problem.

Chucklechops

Thank you FreeBear - that's a really interesting article. I'm glad that I've only paid for the damp survey, and not yet signed on the dotted line for the full damp treatment. The article makes sense, because my house has been empty for a few years (with no heat). Thanks again, this looks like it will save me a lot of money.

FreeBear

Just a thought, if the property is listed, the Conservation Officer would be very upset if you go ahead with the work.

Chucklechops

Thanks FreeBear,

There is damp in my lounge and one wall of the kitchen. My bathroom is downstairs, off the kitchen - in your opinion, should I be removing some of the tiles from the bathroom to check for damp there, too? Even though I wouldn't be able to check all of the walls.

Many thanks

FreeBear

A floor plan of the property, and the damp spots marked would help, as would some photos both inside & out.

Also some idea of the age of the property & type of construction (i.e. solid brick or cavity).

The tiles in the bathroom could be covering some damp, but at this stage, I wouldn't suggest removing them. If we can identify the source of the damp, once that is fixed, we can look at other repairs.

Chucklechops

Thanks FreeBear,

I'm going to take some time to think this all through, including reading through the Heritage article again, and doing some further research - there's quite a lot to consider, but there are many people who agree with what you say.

I really appreciate your input.

Chucklechops

Hi FreeBear, and whoever else is interested.

I'm moving back into the house in a month's time, and I've decided to do the following after some more research:-

1. Hire a dehumidifier to kick-start the drying process
2. Have the heating on at a constant 15 C, to avoid a heating/condensation cycle
3. Replace the gypsum plaster in the downstairs rooms with lyme plaster, and clay-based paint, to allow the rooms to breathe
4. Have adequate ventilation - install an extractor fan in the bathroom/make full use of the extractor fan in the kitchen, open windows in spring/summer etc.

I believe this will resolve the issue. Everything in the article makes sense, as the damp problem only happened after the rooms had been plastered with gypsum, which was trapping moisture inside the walls. The fact that my property has been unoccupied (and therefore unheated) for several years has also clearly contributed to the damp problem.

Thank you again for your help.
.

FreeBear

Chucklechops said: Everything in the article makes sense, as the damp problem only happened after the rooms had been plastered with gypsum, which was trapping moisture inside the walls.

Gypsum plasters will allow moisture to pass through, so it is not as bad as some people make out. However, gypsum is water soluble and turns to mush if it stays damp for any length of time. This is where lime plasters have an advantage, especially on solid brick walls.

If you are stripping plaster off the walls, it would pay to fix insulation to the external ones - 50-100mm of woodfibre or cork skimmed with lime would be ideal and go a long way to reducing condensation as well as keeping the heat in. If you can do the bulk of the work yourself, that will help to keep costs down.

Chucklechops

Thanks FreeBear.