Damp Proofing Question

Mould on solid brick masonry external walls

While stripping wallpaper in the flat, noticed some mould in some areas on the external walls. It is an Edwardian property and I believe the external walls are solid brick masonry with an internal plaster finish applied directly to the brick. I could not be certain but I do not believe the external walls have any insulation as they are always cold to the touch. I had intended to just have these external walls re-plastered prior to painting, but I believe that I should dry line these internally with the minimum amount of insulation (we cannot afford to lose too much space internally) required to alleviate this dampness issue. Any advice / proposed dry lining methods much appreciated.

Thank you all for your advice so far.

In response to Scott - does 70-75mm include the small cavity you mentioned? Any need for a vapor control layer in any of this? I assume if we go to this extent that we could use this new 'false wall' to allow for transfer of wiring for sockets and potentially some pipes for radiators / water supply if need be?

thanks again for all your advice.

3 Answers

Best Answer

Hi there,
This is a common problem and in my opinion the best route for repair is as follows. It may seem a bit drastic, but the results are well worth it.
Strip all the plaster from the brick, this will gain you about 1". Leave a small cavity and erect a 3x2 timber stud wall, bracing and stiffening where necessary. Ensure no timber is directly in contact with the external brick wall. Fit 50mm rigid foam insulation between the studs and sheet with Duplex plasterboard. Skim coat plaster, fit skirtings and then decorate. You will lose approx 70-75mm of the width of the room, but the difference regarding heat retention in the room is extremely noticeable. It will also eradicate any condensation issues as you will now have a warm external wall.
Hope this helps
Scott

Answered 12th Sep 2013

Russell Preservation

Member since 10 Apr 2013

Hi there
Hack off plaster,you can purchase polystyrene backed plasterboard the deepest you can allow regarding room size , then dot and dab onto the cold wall,this should take the wall temp above the dew point which causes the condensation,the method of a false wall is a better job but regarding saving space this is another option.
regards
Joseph

Answered 15th Sep 2013

Trident Damp

Member since 26 May 2011

This type of property with solid wall construction would have been built using lime mortar, internally it would have been lime plaster, finished with a lime paint, this would allow your walls to breathe.

If the outside walls have been re-pointed with a cement based material this will trap water in the fabric of the building allowing water transfer from the external brick to the internal brick and into the house.

You can apply insulated plasterboard, this will increase the insulation it will not stop any water ingress from the external wall, the only way to stop this is to remove any cement pointing and replace with a 3.5 or above natural lime mortar, there is no cement in lime mortar anyone who tells you different run a mile from.

The cost of lime mortar is a lot dearer than cement but can still be purchased from specialist suppliers, it is not hydrated lime which can be purchased from all builders merchants but hyrdalic lime, finding someone who can use it might be a tad harder

Good luck Alex

Answered 17th Sep 2013

ADR Property Maintenance

Member since 1 Mar 2009

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