Damp proofing stone basement, what render?

[MaccaTVR]

Hi, looking for some advice / people with experience.

Sandstone house built in 1900, built on a slope. One side of the house has a kind of basement floor, where I would say around half of it is below ground level.

Been getting signs of damp in the walls and floors. Had a company do a damp survey, which they said the room needs tanked. To save money he said I could do a lot of the prep work myself and said I'd need to strip the walls back to bare stone, so they can then apply a render called Sulfacrete then two coats of something called Hydradry.

I've taken all the plaster off which revealed a type of render already on the stone. Parts of the render had big holes in it for electrical sockets and wiring, which also revealed the stonework. Some parts of render was cracked and fell away from the stone.

Damp guy came back and said they won't need to apply a render anymore as he didn't know what was behind the wall when he first did the survey, and the render I have will do - he said it was a cement render. He said they will just fill in any cracks and holes.

So - my concerns...

The best way to describe the stonework is it just looks like a mixture of random sized stones / rubble. It doesn't look like sandstone, nothing how it looks on the outside. It doesn't look like there is much mortar between the stones either, and where there is mortar it's very crumbly.

Should I be concerned at how it looks?

I'm worried that the existing render is actually the wrong type, possibly causing more damage. Is this a sign of moisture / water being trapped between the walls?

How do I know what type of render it really is, but what type of render should I have on the wall?

I've read lime to make it breathe, however won't this actually be bad if I'm trying to damp proof it? Or in other words if a cement render is used to completely damp proof the basement won't the water get trapped behind it and damage the stone?

Thanks in advance

 

[Ivor Windybottom]

Get a different company in. I'm not a basement expert at all, but my understanding is that in order to damp-proof a basement you need a separate wall that doesn't contact the original. Normally they line the existing wall with plastic egg-box type sheeting. The water runs down the back of it then gets collected somehow at floor level. You put plasterboard on the inside of this sheeting.

I doubt very much that any magic coating can keep water out.

Tanking is normally for wetrooms and showers, to stop water from the room getting out into the wall and floor. It doesn't work the other way round. It will either leak or blow off.

It sounds to me like they're intending to make something that lasts until your payment clears, beyond that they don't care.

 

[Ivor Windybottom]

The Difference Between Tanking & Waterproofing - Newton Waterproofing

We are frequently asked the difference between tanking and waterproofing by those looking to convert a basement or cellar into a dry space.

www.newtonwaterproofing.co.uk

 

[Ivor Windybottom]

 

[Ivor Windybottom]

I did use cellar paint on a single-skin garage once, it was a bit damp. It worked really well, but that is totally different to being underground with running water behind.

 

[ree]

OP,
What an odd sounding post #1? Whatever:

Tanking is used over floors and walls in basements - its also used on "wet walls" with showers & tubs - and there's the various particular uses for walls with rising & penetrating damp.

Why not remove all plaster & render back to raw stone work, & then post pics of the basement walls, and the outside of the walls at ground level?

The house you describe is built on a slope so you will be getting gravity pressured ground water attempting to force its way into the basement.

 

[noseall]

Hi, looking for some advice / people with experience.

Sandstone house built in 1900, built on a slope. One side of the house has a kind of basement floor, where I would say around half of it is below ground level.

Been getting signs of damp in the walls and floors. Had a company do a damp survey, which they said the room needs tanked. To save money he said I could do a lot of the prep work myself and said I'd need to strip the walls back to bare stone, so they can then apply a render called Sulfacrete then two coats of something called Hydradry.

I've taken all the plaster off which revealed a type of render already on the stone. Parts of the render had big holes in it for electrical sockets and wiring, which also revealed the stonework. Some parts of render was cracked and fell away from the stone.

Damp guy came back and said they won't need to apply a render anymore as he didn't know what was behind the wall when he first did the survey, and the render I have will do - he said it was a cement render. He said they will just fill in any cracks and holes.

So - my concerns...

The best way to describe the stonework is it just looks like a mixture of random sized stones / rubble. It doesn't look like sandstone, nothing how it looks on the outside. It doesn't look like there is much mortar between the stones either, and where there is mortar it's very crumbly.

Should I be concerned at how it looks?

I'm worried that the existing render is actually the wrong type, possibly causing more damage. Is this a sign of moisture / water being trapped between the walls?

How do I know what type of render it really is, but what type of render should I have on the wall?

I've read lime to make it breathe, however won't this actually be bad if I'm trying to damp proof it? Or in other words if a cement render is used to completely damp proof the basement won't the water get trapped behind it and damage the stone?

Thanks in advance

What are you trying to achieve? Absolute damp proofing or just modest improvement. Don't be drawn in by the claims of damp companies.

The reality is, that unless you spend thousands, prepare to be disappointed. Subterranean basements/cellars are notoriously difficult to renovate.