damp queries

[Tim Smith]

Hi Everyone,

Got a few queries that Im hoping someone might be able to help with...

Im starting to renovate the dining room in our house. When we moved in 4yrs ago the survey picked up a bit of damp in the walls either side of the mantel piece. The damp was repaired and although I didnt watch what they did, the visible outcome was a two new patches of plaster from floor level upto the height of the mantel on either side of the fireplace.

Now - we've had the fireplace removed and Im decorating in preparation for the installation of a hole in the wall electric fire.

First question - having removd the skirting board, there was what looked like expanding foam that the damp people put in when replacing the skirting board. Is this likely to have been for any particular reason or may they have just used it to fix the skirting? The plaster doesnt go right down to the floor so this may have been to keep the skirting vertical this there is no solid fixing - is this likely to be correct?

Secondly, with regard to the fireplace, the fitter who came to do first part of the fireplace install, bricked up the bottom of the original grate opening to create a "hole" in the wall about 50cm up from the floor. Im doing the plaster work around this new brickwork.

Questions

1. There is a series of holes around the outside wall in the bricks just above the floorboard level (floorboards have a 50cm cavity beneath them to hte ground). Im presuming that these holes form the dampproof course. Is this correct?

1. The fitter, bricked up from floor level (just below the level of the holes in the bricks eitehr side of the opening) to the height of the hole - should he have put something in here with regard to stopping damp or does this not matter as this is merely the front of "proper" chimney opening?

2. Where the hearth was there is a concrete slab which (on looking under the floor) is supported on bricks going down to the soil under the floor. As this slab was slightly below the floor level, I levelled it using levelling compound. Now a small area of the levelling compound near where it meets the wall (and to agree the new bit of wall the fitter built) is showing signs of being damp - they are a darker colour but not physcially damp. As the concrete slab is below the dampproof course, Im assuming that this is to be expected - is that the case?

1. I was intending painting with waterproof floor paint and putting some polythene down before carpet goes down. Is this the best course of action? Alternatively, I can take out the levlling compound i put in, and put a layer of a waterproof membrane underneath some new levelling compound?

Many many thanks for your thoughts...

Tim

[mail]

Determine if this is render or gypsum Probable cause of damp was likely to be hygroscopic salts from fossil fuel burning but may have been other sources If gypsum consider seriously replacing in sand cement with silicatious water proofer

from floor level

Nothing to do with damp per se - more likely to be cheap and cheerful gap filling could be they are plonkers and tried to "glue" it with foam - I have seen that done!

or may they

It depends if you are talking about glue or foam difficult tocomment without seeing

The plaster doesnt go right down to

Quite right that is good practice maybe they are ok reason is to stop bridging

so this may have been to keep the skirting vertical

no

this there is

not sure if you mean a timber ground or nails

timber grounds ( a solid fixing into which you put screw or nail) should not be used you can use glues or screws or skewed nails

I use a dpm and screws with Fischer type or Rawl type fixings

make sure it is render not plaster

It may well be correct that it is holes for a dpc but they are in the wrong place Look up BWPDA Code or Practice or BS Standard for correct location of dpc If they are angled down at a steep angle you may just be ok

Yes normally a physical dpc but you are not alllowed anything combustible too near a fire and I cannot visualise what has been done

or does

dont understand - send a piccy or put one on line

How do you know use a meter to be sure If it is coloured it is likely to be wicking damp damp may be from below or water from recent works eitther way there should not be any link

use SBR and SIKA No 1 in the mix and redo that bit or put in a dpm

As the

yes but it will be bridging unless isloated or replaced consider merits of rebuilding it on insulation?

Not a bad idea if it is proper dpm modern equivalent of Syntha prufe or an epoxy resin ~Woulnt bother with teh polythene

and putting some

Just make the new leveling compound water proof as suggeseted?

Chris G

[Tim Smith]

Hi Chris,

Many thanks for the reply.

Im not sure whether the work done by the Damp Proof people was render or gypsum but when I was creating a channel for some cable conduit, quite a large area came off on one side. Additionally, as the new skirting is slightly lower than the old one, I need to take the plaster a little all the way round the room.

What I have started so far, I did using Bonding Coat - from what I understand of your reply, this should be render. Can you explain why? If necessary, what mix sand/cement would you recommend and could you suggest where I might get a "silicatious waterproofer" - do you have a brand name?

Im inclined to agree that they were using this to try and fix the skirtings. There are some timber grounds but this is probably some type of gap filling technique like you usggest.

Ive emailed you the photo since Im sttruggling to get it online at hte moment. Imagine, an opening that you would noramlly have for a fireplace grate - perhaps 50cm wide and 80/90cm high. He has simply put two or three courses of brick across the width of the opening to allow for a hole in teh wall. The picture doesn show clearly as Ive plastered but the openining is a wide as it ever was, it just went down to the floor before.

Im a bit concerned now about exactly where about the damp proof course is and whether the drilled holes do form part of it - the house is 1930's so they arent likely to be original. Surely, if the brick/concrete plinth is in contact with hte wall, the ground and then upto floor level, it in itself would be breaching any DPC that was below floor level?

Thanks for any info you can provide.

Tim

[Tim Smith]

Just to clarify (Ive gone and checked). Although the holes drilled in the wall are just above floor level inside (between the floor and the level of the plaster), they are only 2.5 courses of bricks above ground level outside the house. The earth level inside the house must be significantly lower than that outside the house. The holes on the outside seem to be "plugged" with a plastic cap of some kind and they do go all round the house.

[meow2222]

Suggest looking at

a start

NT