Advice on damp

[JonHeath]

Hi all,

I'm looking for a bit of advice on a damp problem in my lounge.

I've posted some pictures below to show the issue. Basically over the past couple of months damp/mould has rapidly appeared in the corner of my lounge. This is under a large window and adjacent to patio doors. Earlier this year I did a lot of work in the lounge including the removal of a small radiator in this area. So initially I suspected it might be condensation on a cold wall causing this, but there just seems to be too much damp for it to be that.

Anyway I’ve taken the skirting board off and as you can see and the bricks themselves appear dry on the inside. However the plaster is wet. I suspect that water is coming into the brickwork from the outside, so I’ve also posted some pictures of the same wall outside. As you can see the mortar on some of damp course appears poor, and could probably do with re-doing. The seal around the window appears sound (this was also replaced earlier in the year). So I’m not really sure what’s going on. As you can also see there is a air brick which goes through to under the floor.

Thoughts welcome on what to do next. Thanks.

P.S. 1930's house with very little cavity between the bricks.

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• JonHeath
• 9 Jan 2014
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• JonHeath
• 9 Jan 2014
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• JonHeath
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• JonHeath
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[Burnerman]

Can you see where the DPC is? Is the air brick sitting on it, or is on the top of the brick course above?
Just wondering if those flags are a bit high, thats all.....for rain splash and the like.
There's a bit of pointing needed in the corner, but that wouldn't cause what you have.
The plaster will suck the water from the brick, making the bricks appear to be dry.
How easy is it to lift a couple of adjacent floorboards?
John

 

[Blagard]

My guess is that you have a one brick thick wall (in Flemish bond), that's about 9" without the plaster and also known as a solid wall. Your DPC will almost certainly be just the 2 courses of blue engineering bricks. The airbricks indicate floor level is most likely at the same level as the top of the "blues"

I would not be surprised if this is a combination of the very wet weather causing the brickwork to be wetter than usual and so colder than usual. The abundance of headers in the brick bond would mean water absorbed by the brick can transfer all the way through the wall at regular intervals.

With the wall a little damper and colder than usual I believe you simply have a lot of condensation going on.

Try killing the mould with a capful of bleech in a bucket of water to wash it off - A method I was told to advise people of many years ago but have never had to do it myself.

Other than that it is just the usual defence against condensation - Heat and ventilate

You probably don't have quite as many headers going all the way through as seen from the outside - quite a few may be "snap" headers, i.e. half bricks

 

[JonHeath]

Thanks for the replies.

I’ve not seen the DPC but I’ll see if I can have a closer look.

The floor is Amtico so can’t come up now that it’s down. The problem area is in a small extended area of the lounge. The main lounge is carpeted. There is a hatch in the floor just in front of that TV cabinet where I can get into the floor cavity (see pic below). However there is a wall under the floor which prevents me getting proper access to the damp area, although I could possibly see it through a gap in the under floor wall.

I thought the same about the patio. It’s been extremely wet recently and it might be a case of water sitting against that outer wall has made it’s way in.

The wall is definitely two bricks thick with little gap. We’ve killed the mould once with the method suggested but it’s come back (as per the pictures) in a matter of only a couple of weeks.

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• JonHeath
• 9 Jan 2014
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[Blagard]

<snipped>The problem area is in a small extended area of the lounge. The main lounge is carpeted.

The wall is definitely two bricks thick with little gap. We’ve killed the mould once with the method suggested but it’s come back (as per the pictures) in a matter of only a couple of weeks.

When was it extended?

The wall at best will be two half bricks thick with a cavity. A "solid" wall has 2 half brick skins with about a 1/2" gap between them and with headers here and there to tie them together. The problem with that small gap in sold walls is it gets loads of mortar in it allowing dampness to cross.

 

[JonHeath]

<snipped>The problem area is in a small extended area of the lounge. The main lounge is carpeted.

The wall is definitely two bricks thick with little gap. We’ve killed the mould once with the method suggested but it’s come back (as per the pictures) in a matter of only a couple of weeks.

When was it extended?

The wall at best will be two half bricks thick with a cavity. A "solid" wall has 2 half brick skins with about a 1/2" gap between them and with headers here and there to tie them together. The problem with that small gap in sold walls is it gets loads of mortar in it allowing dampness to cross.

By that definition I would describe it as a solid wall. Sorry I'm not hot on terminology. It is basically two bricks thick with at best a half inch gap between. The bricks are turned 90 degrees every so often to join the skins (presumably this is what you're calling headers). I've bricked/blocked a window up on the opposite side of the extension so I've seen it myself.

I'm not sure on an exact extension date. However there is no record of it being added, and it has the same roof tiles as the original roof. The original house was built in 1938 and planning records began in 1948. So I'd say somewhere in between those two dates. The street is full of these little extensions.

 

[catlad]

My advice is screw some pl4000 celotex or equivalent to the wall and re skim it.

 

[Flyboytim]

It is condensation occurring on the inside surface of a cold solid exterior wall. It is neither penetrating, nor rising damp, and is unlikely to affect the plaster seriously.

Your damp course of blue engineering bricks is (doing its job as a DPC, but also) preventing the moisture that has built up in the walls (from rain etc) from descending any further, and the evaporation occurring outside is chilling the bricks, creating a cold bridge on the lower wall. Being slightly recessed on the inside, that bit of the wall is not in a natural draught, so the air inside stagnates, cools and deposits moisture, encouraging mould growth. The same effect may be found in corners and behind furniture, or inside cupboards.

To remove the mould, the spores need to be sterilised. Diluted bleach will kill the mould, but will not sterilize the spores, which will regrow when conditions allow.

With a clean nylon paintbrush or mini-roller with disposable roller, use thick bleach undiluted, just lay the bleach on to a few inches above the current height of the mould, cover the area to the floor, and allow to dry. Do not use a natural bristle brush, or one that has any paint residue, and do not scrub the area you apply bleach to. The bleach will discolour then bleach the mould as it soaks in and dries.

Bleach is somewhat acid and should not affect most paints of vinyl, acrylic and polymer composition. (Bleach naturally gives up part of its chlorine as it dries, leaving behind sodium chloride - common salt - which will deter the establishment of moulds. The small amount of detergent in bleach will allow the bleach to penetrate where possible, at least to the extent that the mould penetrates.)

Treat the skirting with neat bleach in the same way and allow all to dry before re-fixing the skirting. Repeat the application of bleach, in situ, and again allow to dry.

Use a desktop fan (i.e. unheated) to increase ventilation in the area in cold and damp weather. Similar use of a fan will help prevent condensation on windows and frames, as will undiluted bleach to stop black mould in those areas, and on grout between tiling, etc.

The most effective preventative measure would be to provide some insulation and cladding to the full extent of the exterior wall, effectively providing cavity insulation, where none is provided by a solid brick construction. This will have long term positive effects regarding energy savings too.

[/u]

 

[JonHeath]

Thanks for the advice. I did wonder if it was condensation but it seemed like such a lot of damp to have been solely caused by that. Wouldn't I expect to condensation on the window above the damp, as well as the patio doors next to the area?

We will bleach, but I would like to try and do something to prevent this happening in the future. When you say insulation and cladding, what type of cladding were you thinking about?

Cheers

 

[Flyboytim]

I've seen council (Hounslow) properties given a complete extra skin of brickwork over the insulation batts that have been applied to exterior of the solid walls. Here's a link to a slightly less elaborate solution:
http://www.markgroup.co.uk/homeowners/insulation/external-wall-insulation
One of the images on this webpage shows brick slips of about 20mm thickness applied to adhesive on the insulation slabs fixed to the old wall, and then mortar is applied between the slips to appear like normal pointing.
There may be grants available to assist with the cost.