Before we use chemical DPC injections.... Please help us!

[weboughtalemon]

We bought a 1830s house. Big regrets!!!!

There is damp everywhere. The red lines are showing the walls where we have damp... You will also see the water mark under the mirror in the hall.

It is assumed there is no DPC anywhere in the walls.

There is a DPM under the screed in the hallway. This doesn't meet the walls (see photo with the green arrows showing where the DPM ends).

There is no DPM in the garage. The wall between hall and garage is soaking wet. In fact, every wall in the garage is soaking wet.

We don't see any other option that using DPC injections to fix the rising damp - Thoughts please??

 

[a twig]

A

Thread 'I’ve just bought an old house and it’s damp, help!'

Dec 10, 2022

So, many people have suggested over the years this should just be called the “old damp house forum”

So I thought I should start a basic guide to tackling damp in a period property that hopefully the learned members of this parish can add to, and we can then point others to in the future:

Broadly, no matter your house, the rules are the same. As a rule of thumb steps 1 & 2 are the cause of the majority of damp issues.

Stage 1 - External
1) Check and resolve any sources of external water ingress at the top (failed roof, gutters, gullets, roof valleys etc)

2) Check exterior vs...

• a twig
• Replies: 2
• Forum: Projects

• 

 

[Matt Green]

Given the height of the damp marks and by the looks of that image the plaster has been run into contact with the floor. That is not a typical groundwater damp profile.

There should be a gap of 50mm between the floor and the base of the plaster at the wall/floor junction to allow water to evaporate behind the skirting. I would suggest removing the skirtings and hack off a 50mm channel around the base and wait for the summer to pass- that might well dry it out in conjunction with lowing any external ground levels as suggested in Twig's guide.


-Matt

 

[aockenden]

Walls don't need DPCs to stay dry at the bottoms. They need appropriate ground levels, appropriate drainage, and appropriate plasters, renders and paints internally and externally. Then normal heating and ventilation of a house does the rest.

The first step is fixing any high ground levels, any drainage or rainwater-goods problems, AND confirming that the walls ARE actually damp and not just salty from old moisture problems that may now be resolved. It sounds like you may have had a damp-survey and they likely stuck a pronged damp-meter thing into your walls, which can give faulty signals if there are conductive salts present. Touch the potentially damp parts of the walls. Do they feel particularly cold / clammy? Are there active molds or mildews present?

Once you've dealt with everything above, a good non-nuclear option for people with damp bottoms of walls on the ground floor is to hire a good lime plasterer to strip-off the bottom 2 - 3 feet of existing junk which will almost certainly be coating the walls both inside and out (cement, gypsum, and plastic paints), and then replace it with lime plaster which will allow the moisture trapped in the walls to finally escape.

Watch this video. It shows the general process:

 

[Lacan07]

if you're screed DPM is ineffective the floors are likely pumping water into the surrounding walls i'm afraid to say.

 

[Flyfisher]

Once you've dealt with everything above, a good non-nuclear option for people with damp bottoms of walls on the ground floor is to hire a good lime plasterer to strip-off the bottom 2 - 3 feet of existing junk which will almost certainly be coating the walls both inside and out (cement, gypsum, and plastic paints), and then replace it with lime plaster which will allow the moisture trapped in the walls to finally escape.

This ^
We had an internal wall that was damp and the paint was blistering off it. We stripped the bottom 2-3 feet back to the brick and discovered it had been cement rendered and gypsum skimmed then painted (probably with a modern vinyl paint). It was replastered with lime (actually a chalk/lime plaster) and painted with a casein distemper paint. Nearly 10 years on there is no sign of damp and the paint has not blistered.

I've little doubt that the original source of moisture from the shallow foundation and no DPC is still there but the wall can now breathe easily so there is no build up of dampness.

The frustrating thing is that it is not significantly more difficult of expensive to have done things properly the first time compared to the disruption of re-doing it all again, but that seems to be the way of things with old properties and we can only hope that word is gradually getting out about the importance of breathability versus 'damp proofing' so that over time the stock of older houses are in better condition for the future.

 

[DaveG]

Just to add, don’t use chemical injections. They don’t work so save your money.
It would be useful to know a bit more about the house. Was it occupied much prior to your moving in? What ventilation if any do you have?
Was it previously suspended timber floors? What’s immediately outside the house in terms of ground levels etc?