Victorian Lower Ground Floor Flat - any ideas for floor build up?

[dodgem]

Hi all,

I live in a victorian lower ground floor flat.

I think the house was converted from a 3 storey house to 2 flats in the 1950's.

My flat had some waterproofing work done in the late 80's early 90's (I think).

The current floor build up from top to bottom is vinyl > 50mm screed > plastic sheeting > 100mm slab > earth.

Theres been damp detected in some of the walls and where the plastic sheeting is failing in the ground.

I want to rip up the entire floor system and replace with underfloor heating.

In terms of damp proofing, can anyone suggest if I need to comply with anything in terms of building regulations?

I am thinking of going with a breathable limecrete sub floor and limestone flagstones as I prefer to let the flat breath.

However - one wall in the flat is about 1.5m underground and has earth the other side, and was thinking of applying a water proof membrane to this but not sure how it would connect to the breathable floor.

Any advise would be really welcome!

 

[^woody^]

For starters, forget a breathing floor. Floors don't breathe, and should be choked if anything.

Below ground waterproofing should be designed, not made up.

Building regulations required for the insulation and maybe damp proofing.

 

[dodgem]

https://www.limecrete.net/limecrete-solid-floor/

This is the breathable floor I found - using geotextile membranes rather than solid membranes which the manufacturer claims meets/exceeds building regulations.

I am waiting for the manufacturer to confirm if it's suitable for flats with one retaining wall below ground that has a waterproof liquid membrane applied to it.

The existing floor, within the flat, has no insulation so I don't think I need to add insulation in the existing areas - for building regulations.

However - the new extension will definitely need an insulated floor slab and I was going to use the limecrete solid floor system again in conjunction with a waterproof membrane to the retaining walls in the flat.

Apart from some damp issues - condensation levels are really high and wondered if there are any alternative to mechanical ventilation?

Are the use of airbricks to let moisture out enough? Am concerned there will be alot of heat lost.

 

[^woody^]

I can't understand why you think a floor needs to "breathe".

It sits on the ground, with an impermeable barrier under it, so does not have moisture passing through it. That limecrete is a complete waste of time, and just installing an inherently damp slab for no reason at all.

If you are renewing a ground floor then insulating it must be considered, and done unless you can prove it's not viable, and building regulations are involved

 

[clifford1]

If a floor is damp from sitting on earth then in an ordinary room, an entirely impermeable barrier simply forces the water up the walls. Hence having a breathable floor allows the damp to evaporate.
A sub-basement however is likely to be surrounded on 5 sides by damp or wet earth, so it has to be either entirely tanked or lined with waterproof membrane or something that does the job, or else lined but having designed water chanels under the floor with a sump that is automatically pumped out.

As I understand the OP his flat has only one wall backed by earth but the rest is not, so the system adopted has to be a compromise appropriate to both situations.

Finally, breathable relates to water vapour, which is not the same thing as penetration by liquid water. In a way that I never really understand, a suitable barrier membrane can block the transmission of water (eg rain) in one direction but still permit breathing (eg damp air, potential condensation, breath) in the other.

 

[^woody^]

If a floor is damp from sitting on earth then in an ordinary room, an entirely impermeable barrier simply forces the water up the walls. Hence having a breathable floor allows the damp to evaporate

WTF? Breathe damp into the room from the ground below?

Anyway, a floor does not "force" water up a wall. The laws of gravity (and some others) apply.

 

[clifford1]

Anyway, a floor does not "force" water up a wall. The laws of gravity (and some others) apply.

Capillary action. It runs out of force at about the height of a sequoia.

 

[JohnD]

Capillary action. It runs out of force at about the height of a sequoia.

provided it is a single, very narrow tube from top to bottom. If the pore size is bigger, or if the route is obstructed by pore size changes from small to large, as happens at every brick/mortar joint in good clean brickwork, it climbs far less. Which is why a cavity wall full of sandy builders rubble, or rendered, or in contact with soil, is much damper than good clean brickwork, and dries out when cleared.

 

[^woody^]

Capillary action. It runs out of force at about the height of a sequoia.

Capillary action is not a force, it's a process, and reliant on the material pore linings, not hydrostatic pressure pushing water.

 

[clifford1]

"Excess moisture is a common problem in buildings, and may be apparent from; damp patches, mould growth, mildew, salts, staining, ‘tide marks', blistering paint, bulging plaster and so on.

Rising damp is caused by capillary action drawing moisture up through porous elements of a building’s fabric" - Designing Buildings website



"A concrete floor inside a building to replace an older breathable floor means ground moisture is forced out to the walls, increasing the damp within the walls." - Why Buildings need to breathe

 

[^woody^]

"Excess moisture is a common problem in buildings, and may be apparent from; damp patches, mould growth, mildew, salts, staining, ‘tide marks', blistering paint, bulging plaster and so on.

Rising damp is caused by capillary action drawing moisture up through porous elements of a building’s fabric" - Designing Buildings website



"A concrete floor inside a building to replace an older breathable floor means ground moisture is forced out to the walls, increasing the damp within the walls." - Why Buildings need to breathe

Googling for random things and trying to shoehorn them together is not the thing to do.

You stated that an impermeable layer under a floor forces water up the walls. It does not. Capillary action is a completely different process to hydrostatic pressure. .

You also inferred that a concrete floor should breathe into the room, which is complete nonsense. A ground bearing floor should be dry, not breathing damp from the ground below into the room above. I just can't understand why anyone would think otherwise.

 

[catlad]

Most people would probably complain if it did.

 

[^woody^]

Most people would probably complain if it did.

Not the Director of Limecrete after gulible people have fallen for his bullshiit.

 

[dodgem]

Hi - I'm the OP. Thanks for all your comments.

My concern has always been that if you tank the floor - water will always rise up the walls - creating rising damp.

The existing old plastic membrane (wpm) in the floor, has already forced some damp to rise up in the walls already - walls that are above ground floor level.

The one wall - that is below ground -has the most damp due to lateral water from soil from the side.

The idea behind the limecrete breathable floor system means less moisture forced to rise through the walls.

I think limecrete system is a good concept, however I'm concerned about:
1) the 1 retaining wall which is about 1.5m underground.
2) if the system relies on excellent ventilation - which is currently poor as flat - or whether the moisture is managed below ground.

When I spoke to Limecrete about it, they suggested adding a DPM to their floor system to lap to wall tanking to the retaining wall.

This is what Limecrete told me:
"In some instances a DPM has been incorporated to join with the wall tanking, this would normally be positioned below the screed so you still get the benefit of the foam glass being the functional moisture management layer."

So seems like Limecrete are suggesting that the foam glass layer manages the moisture below ground.

P.s. I prefer not to use cavity walls and sump pumps - due to expense and loss of m2 - as the 1 bed flat is already tiny.

 

[Nakajo]

My understanding is that if you whisper negative messages into a bottle of water, and then show that water to the walls, this will be equally effective.