Penetrating damp - how do you remedy it before insulating?

This house ! :grimacing:
On the face of things it was a problem free house when we bought it, yet now it’s showing a number of problematic and concealed flaws which are all moisture related problems.

Another problem has arisen, which is causing us to think we have penetrating damp coming through from the external walls into the plaster.
We initially thought it was cold wall condensation, but a recent exploding plug socket has caused us to look closer and think differently.

So what to do ?
Number one - we’ve isolated all the upstairs plug at the mains and our electrician is coming tomorrow to remove the plug socket and re-site a new one to a dry wall!!

We planned to insulate the cold walls in the bedroom to eradicate the condensation…
We knew we’d have to hack off all the affected plaster, but have no idea which insulating materials and plaster we should use.

A recent observation from a knowledgeable friend, pointed out the radiator pipes embedded in the plaster on the cold wall , would be drawing moisture into the plaster - those pipes need to come out of the wall.

The window is also very poorly fitted - water could be penetrating around the frame from the outside.

The brickwork and mortar outside seem in good condition, but a couple of electrical outlets might be enabling water to track in.

Finally , the house is over 130yrs old, we’re wondering if the bricks have become porous, yet no spalling is evident. Porous bricks has made us wonder about sealing the bricks, but with a building built to breathe - is sealing the bricks wise?

Lots of questions and not enough money to keep up with the barrage of problems means we’ll definitely have to tackle a lot of this installation ourselves.

…the bricks? To seal or not to seal?
…moisture management ? Do we fit a vapour control layer or a barrier?
…insulation ? What materialst do we use to prevent heatloss and mitigate against condensation
… The plaster finish ? Do we use foil backed plaster board, insulated board or lime plaster to breathe as the building intended.

Oh dear, those sockets aren’t pretty.

As part of the preparations for IWI you need to move all sockets, fittings, other penetrating objects from the outside wall and preferably not within one metre on the wall touching the outside wall.

Do not seal the outside wall. That is the path to trapped moisture. You may need to waterproof it, which is different.


for my suggestion bearing in mind I haven’t seen your wall close up. It should waterproof the wall and let it breathe.

Hi, my first instinct is to find the source of moisture. If you have any sort of drawings of the house layout that would be a good start to look at activities and moisture generation (vapour rises and condensation drips). This will give an indication if the problem is external or generated internally from activity change. We once experienced horizontal rain that came through the passive air vents in our double-glazed doors – you had to see it to believe it. I would look to use a borescope or dismantle a section of skirting/ flooring to see what is behind the affected area. Best to find the moisture source before thinking of the solution. The IR camera may be useful to pick up cold / damp and hot spots.

1 Like

Whilst using StormDry wouldn’t do any harm if not needed (unlike some remedies) I am assuming penetrating water (not necessarily rain). As @lloydham says, it is best to find the cause first.

Incidentally, what room is below the damp area? Is it by any chance one with high humidity generation, such as kitchen, shower or sauna (I should be so lucky)?

1 Like

It appears there are a number of sources for the moisture
The electrician came today; when he removed the wet socket, the mortar at the back is wet. I think it’s penetrating in from outside .
We inspected outside and around the window, (sited above the socket to the left), there is a hole in the mortar and the seal around the window is heavily degraded.
In addition to this - the radiator pipes under the window are in the plaster wall - which are another potential cause of moisture being drawn in - Learned that info at the #LloydHamSchool​:grin::muscle:t3: So we’re getting that sorted.

Quote - cndensation drips down. I think we have that problem too, because the beading for the laminate was wet on the floor. Also I attached a picture of the paintwork to show how the wall is affected…

We know both the walls in that affected corner are exterior cold walls and are sometimes wet when we wipe them down to get rid off the blackspot mould.
The important thing for now is the electrics have been made safe and the socket fully removed from the wall.

Our next stop is get a new window fitted - we know we need one.anyway - and inspect and repair the pointing.
After that we’ll watch and see what happens.
I wonder about insulating those walls or replacing the plaster with other to prevent the cold wall condensation situation.

It’s the hallway and stairs underneath - these areas and the bedroom are on the gable end and front corner face of the house.

As the damp in the walls is clearly not rising damp there should be negligible salts dissolved in it, so there shouldn’t be an urgent need to replace the plaster. As you have identified the window/wall join, a hole and dodgy pointing I suggest waiting for those to be remedied. Use a dehumidifier in the affected room and wait as long as your patience holds out for any improvement.

When repointing include plasticiser and waterproofer in the mortar mix or use

1 Like

I’ve just noticed that you have older plaster with a modern skim coat. The base may be vapour open and the skim is not. That could be contributing to an accumulation of damp, as the original Victorian structure would have “breathed”.

And this brings about the question that’s I’ve been debating with myself
Do we go back to original breathable ?
OR do we use the modern less breathable materials to make this old house watertight? Would this route require us to move away from breathable materials altogether?
Do the Stormdry products block and seal the pores in the bricks…and will the plasticisers for the cement do the same ?
And if they do, does that mean we insulate with a non-breathable material and plaster over that with foil backed plasterboard or such like.
I know the paint hasn’t helped the case for breathing - it’s vinyl silk.

I think we have original lime plaster in the back room around the window - it’s the only window that doesn’t suffer a condensation problem.

What would you do?

The easy questions first. The Stormdry products do not block the pores, unlike sealants. This brings me to my first post above where I distinguished between sealants and waterproofers. Tests show that about 2% of “breathability” is lost. Sealants loose about 98% to 100% breathability if I remember correctly.

Any building has to be watertight, as in liquid water, but see below about vapour.

Now the trickier bit!

A structure that was designed to “breathe”, although unintentionally, needs to breathe unless a very skilfully designed and executed conversion plan is carried out by absolute experts. Breathing buildings can be airtight ones at the same time. This is because what these breathing buildings “breathe” is water vapour, not air.
It is a common belief that buildings need air but that isn’t so.

So, how is airtight and breathable possible at the same time? Easy peesy. The gaseous molecules of air are mostly larger than water molecules, so all you need to do is make your home airtight with layers that water can get through (so will hydrogen but we can ignore that) but atmospheric gasses can’t.

Although modern products are available that do this there are traditional ones that coincidentally do too. Or maybe it isn’t coincidence. Our ancestors would have discovered what products lead to a lasting comfy home by trial and error without understanding the science.

As luck would have it, 2cm or more of lime plaster or lime render meet the requirements. Assuming no gaps or cracks. In practice you need gaps to get in and out of and to let the light in, so special attention needs to be given to joins. Also, you can’t quite touch floorboards with the plaster as the boards expand and contract and damage the plaster, but get as near as possible and seal the gap with a suitable modern product. I suggest laying some cardboard on the floorboards and plastering to them and then after removing the cardboard add flexible sealant.

1 Like

:heart:The scientific explanation ! Thankyou


So, how is airtight and breathable possible at the same time? Easy peesy. The gaseous molecules of air are mostly larger than water molecules, so all you need to do is make your home airtight with layers that water can get through (so will hydrogen but we can ignore that) but atmospheric gasses can’t.

Now have the answer :muscle:t3::100:

1 Like

Do you have a picture of the exterior? An angle up to the eves/gutter would be ideal. Is it on the weather side of the building?

A draft passing through the electrical box along cracks surround the cables or chase to the floor system could be significant, usually this effect is much worse with dot and dab.

What’s in the room below the outlets?

Have you taken any measurements, with a hydrometer or thermal camera? You can detect drafts with a warm wet finger - so it needn’t be high tech.

At the moment there isn’t enough to make an informed decision. Although all measures would be worthwhile if you’re going for significant quantities of IWI.