Stormdry paint vs lime render for external walls

[HSK]

Hi. I wondered if anyone could provide some insight into what option is best to reduce internal wall damp and mould due to cold walls.

For context, weve been living in a 1930s semi detached property for almost 7 years and throughout this time weve had some mould issues on several walls in the house which come about every year in the cold months. Weve fitted a PIV unit a couple of years ago and thats helped with ventilation and reducing condensation but some parts of walls still get damp and mould build up. We had a company come round to assess what can be done and theyve suggested a coating of Stormdry Masonry Protection Cream around the external walls (after the cracks, holes and gaps have been repointed and the wall has been cleaned), as they say this will provide help seal any gaps and provide some insulation and warm the internal walls. Our external walls currently are a mix of brick and painted and exposed pebbledashing, so not a consistent look. So whilst the StormDry option seems like a potention solution, my concern is that (even with the relevant tidying up and repointing) the StormDry will be sprayed over uneven surfaces and not look smooth. The other option we were thinking about was rendering the outside as this would give a smoother neater finish but were advised against this by the company as they said it wouldnt be breathable and would trap any existing moisture. Having done some research it seems lime render is breathable, more flexible and does help with providing some insulation.

So my question is, does anyone have any experience of using either the StormDry cream or having lime render used as a solution to internal wall damp and if so, which would be the most suitable option? If anyone has put in lime render, is it known to be breathable and has it stopped any internal wall damp/mould? Interested to hear peoples thoughts and experiences.

Thanks in advance

 

[JohnD]

Where do you think the water is coming ftom?

Is it steam from a bathroom, or water from damp washing drying indoors? A hidden plumbing leak? Spilling gutters?

 

[endecotp]

theyve suggested a coating of Stormdry Masonry Protection Cream … provide some insulation and warm the internal walls.

Nope. Applying cream to the walls will not provide any insulation.

lime render is breathable, more flexible and does help with providing some insulation.

Not much insulation, unless it is a specific insulating render with tiny glass beads in it or something.

You need to determine whether (a) the walls are cold, resulting in condensation, or (b) the walls are leaking water. Or both. What you need to do depends on what the problem is. If you post some pictures of the damp patches, inside and out, someone will express an opinion.

Beware of “damp companies”. Some are absolute scam merchants; even the better ones tend to pick up on things that they happen to have a solution for, when your real problem might be quite dofferent.

 

[JohnD]

theyve suggested a coating of Stormdry Masonry Protection Cream around the external walls (after the cracks, holes and gaps have been repointed and the wall has been cleaned),

If you have a defective wall, it needs to be repaired, regardless of any potion somebody wants to sell you.

 

[HSK]

Thanks for your replies all. The condensation seems to be appearing due to cold walls every autumn/winter....so heat from everyday living like cooking, showering, etc attaching itself to cold parts of the walls, causing condensation. Even with open windows it doesnt stop it from appearing (due to cold temp outside). The majority of the damp appears near edges of walls, in corners of rooms and on walls where there may be some furniture in front of it. We dont have any spilling gutters or leakages outside but do have some cracks on the external walls which do need reparing (although arent directly next to where the internal mould is). So were looking for solutions that can increase the wall temp which were hoping that, combined with the PIV, will help...but not sure what the best possibel route is.

 

[endecotp]

What is the construction of the wall? Does it have a cavity?

 

[JohnD]

Where do you think the water is coming from?

 

[HSK]

I believe the walls are a mix of brick and cavity walls.

Its difficult to pinpoint exactly where the moisture is coming from. I think its a mixture of some coming in from external cracks on the outside of the house (however i think thats minimal) and warm air hitting cold walls (this being the primary reason) during the autum/winter months and having little way to escape.

 

[StephenStephen]

As an amateur, I think the stormdry will make things worse, unless there are particular reasons to believe that this is penetrating damp.

My understanding is that lime based walls move water from the inside (generally higher humidity) to the outside (generally lower humidity). Stormdry will prevent that, causing more damp.

I personally wouldn't have anything to do with a company which suggested spraying stormdry on unless they'd identified the particular peculiar circumstances (for example; Southwest wall facing the sea perhaps) justifying using it.

It sounds like you're fairly confident that the problem is condensation, so if it is that then ventilation and insulation will help.

EWI would seem like the technically best solution, but it would need to be able to move water through it, and I think (I don't know) can be hugely expensive and disruptive.

So, some sort of internal insulation would seem like the way to go - dry lining, or lime-based insulating plaster (eg; cork, hemp or mineral admixture).

Having said that, is the internal plaster lime or gypsum based? If it's gypsum based, then there's not a lot of point on the extra time and expense of using lime, so dry lining seems to be the way to go.