We had planned on having a new flooring laid last week in our hallway, but on lifting the old carpet the installers noticed that the floorboards were very loose. They tried to secure them, but in lifting them they noticed that the concrete slab on which they were sat was perishing.

House is a double fronted 1905 build, with the concrete slab only running through the central hallway (lounge / dining room on left and right of hallway have suspended floors on joists).

I don't know why the hallway had a slab in there - perhaps to support the stairs which run up the middle of the house?

Anyway, clearly the concrete wasn't well protected from any damp, and the moisture has risen and caused some small damage to the ends of the joists for both of the adjoining rooms.

It would appear there are two choices - dig out the slab, and replace with a damp-protected new slab. Or dig out the slab, and replace with a suspended floor. Second option has advantages for us in that we'd be able to get the new flooring down soonish, whereas I'd expect to have to leave a concrete slab for a period of time (2 months?) before putting the solid floor on top of it (not a laminate, but similar). Is there a half-way house of some form of using some pre-cast blocks to fill the hallway subfloor instead which might speed things up?

I presume the concrete slab which has failed runs straight through to the back of the house too; and would expect that the bits I can't see suffer from the same issues that the bits that we can. Where I can access under the stairs there doesn't seem to be an issue. How concerned should I be to investigate the whole lot?

Total floor area of the hall is only about 1.2m x 3.5m, so not a large area.. Pain in the arse though!

Matt

On Mar 14, 2:16*pm, larkim wrote:
We had planned on having a new flooring laid last week in our hallway, but on lifting the old carpet the installers noticed that the floorboards were very loose. They tried to secure them, but in lifting them they noticed that the concrete slab on which they were sat was perishing.

House is a double fronted 1905 build, with the concrete slab only running through the central hallway (lounge / dining room on left and right of hallway have suspended floors on joists).

I don't know why the hallway had a slab in there - perhaps to support the stairs which run up the middle of the house?

Anyway, clearly the concrete wasn't well protected from any damp, and the moisture has risen and caused some small damage to the ends of the joists for both of the adjoining rooms.

It would appear there are two choices - dig out the slab, and replace with a damp-protected new slab. *Or dig out the slab, and replace with a suspended floor. *Second option has advantages for us in that we'd be able to get the new flooring down soonish, whereas I'd expect to have to leave a concrete slab for a period of time (2 months?) before putting the solid floor on top of it (not a laminate, but similar). *Is there a half-way house of some form of using some pre-cast blocks to fill the hallway subfloor instead which might speed things up?

I presume the concrete slab which has failed runs straight through to the back of the house too; and would expect that the bits I can't see suffer from the same issues that the bits that we can. *Where I can access under the stairs there doesn't seem to be an issue. *How concerned should I be to investigate the whole lot?

Total floor area of the hall is only about 1.2m x 3.5m, so not a large area. *Pain in the arse though!

Matt

Concrete is usually workable with after several days. Do get plenty of
insulation under it.


NT

On Wednesday, 14 March 2012 19:19:22 UTC, NT wrote:
On Mar 14, 2:16*pm, larkim wrote:
We had planned on having a new flooring laid last week in our hallway, but on lifting the old carpet the installers noticed that the floorboards were very loose. They tried to secure them, but in lifting them they noticed that the concrete slab on which they were sat was perishing.

House is a double fronted 1905 build, with the concrete slab only running through the central hallway (lounge / dining room on left and right of hallway have suspended floors on joists).

I don't know why the hallway had a slab in there - perhaps to support the stairs which run up the middle of the house?

Anyway, clearly the concrete wasn't well protected from any damp, and the moisture has risen and caused some small damage to the ends of the joists for both of the adjoining rooms.

It would appear there are two choices - dig out the slab, and replace with a damp-protected new slab. *Or dig out the slab, and replace with a suspended floor. *Second option has advantages for us in that we'd be able to get the new flooring down soonish, whereas I'd expect to have to leave a concrete slab for a period of time (2 months?) before putting the solid floor on top of it (not a laminate, but similar). *Is there a half-way house of some form of using some pre-cast blocks to fill the hallway subfloor instead which might speed things up?

I presume the concrete slab which has failed runs straight through to the back of the house too; and would expect that the bits I can't see suffer from the same issues that the bits that we can. *Where I can access under the stairs there doesn't seem to be an issue. *How concerned should I be to investigate the whole lot?

Total floor area of the hall is only about 1.2m x 3.5m, so not a large area. *Pain in the arse though!

Matt

Concrete is usually workable with after several days. Do get plenty of
insulation under it.


NT

I think the floor company are concerned that what they are laying would be similar to a tiled floor, so it would seal the concrete in without allowing for any moisture to wick away from the slab. Agree about insulation.

Matt