Filling void underneath suspended floor (damp)

[MartinB85]

Hey Everyone,

I'm currently looking at some resolutions to my suspended floor.
Bit of a background, the house was built about 100 years ago, the hallway and kitchen a solid concrete floors, the living room however is a suspended floor with a void underneath with a slight gradient from from about 500mm at one side to 1000mm at another.

I've had a few issues with this:
- The room gets warm enough with the heating on but the floor itself is cold.
- I had wood worm about 18 months ago in one corner where standing water comes through the wall below ground level and sits on top of the soil at the bottom of the void (it does drain away but very slowly). I had this treated and replaced some of the timber floorboards and have had nothing since but my concern is that this could come back.
- I also had some very small white damp rising, but I think this was because I filled what looked like drilled holes into the existing floorboards that were on one side which probably allowed airflow I re-drilled these and this helped that issue.

My plan is to have an engineer assess the structure of my house and then if feasible remove all the timber Hardcore/Sand blind/DPC/Concrete/Screed the whole area.

I'm looking for a bit of guidance as too wether this is the best solution. There is currently 2 air blocks underneath the floor, and wasn't too sure if filling this way is asking for more trouble damp wise, we have ventilation above the floor as well (air vent, open chimney flu and trickle vents).

As the central heating is run under the current floorboards, would it be a case of filling to a certain level and then putting in some new timbers to create a small void for insulation and pipework?

In regards to the water getting through the lower brick work, I'm unsure if I should be digging down to repair pointing and possibly use the breathable water resistant coating you can use on bricks or if filling the void should block that water from getting in and causing any issues.

Sorry there's a lot of info there but i'm just after any advice before I possibly make the wrong choice!

Thanks

 

[Mr Chibs]

Hello

To make this is a solid floor is a lot of work. Not difficult just a lot to do, your plan doesn't include any insulation, so you'll be replacing a cold wooden floor with an even colder concrete floor. You'll need a lot of material to even out a slope difference of 500mm.

Lots of houses your age (my own included) have had issues with rotten joists/worm, usually a contributing factor is blocked air vents in the the sub floor and no dpc(s) here and there.

You may be better sorting out any issues and insulating your suspended floor... this won't make it warm, but will slow heat loss.

 

[freddiemercurystwin]

Building Control would not permit you to do any compacted layers beyond about 600mm as they will drop.

 

[MartinB85]

Hello

To make this is a solid floor is a lot of work. Not difficult just a lot to do, your plan doesn't include any insulation, so you'll be replacing a cold wooden floor with an even colder concrete floor. You'll need a lot of material to even out a slope difference of 500mm.

Lots of houses your age (my own included) have had issues with rotten joists/worm, usually a contributing factor is blocked air vents in the the sub floor and no dpc(s) here and there.

You may be better sorting out any issues and insulating your suspended floor... this won't make it warm, but will slow heat loss.

I was initially thinking of just insulating between the joists, I'm hoping at some point we'll be extending in this room and it will turn into a kitchen diner (currently on use it as my office and gaming room) so once it's a kitchen it will need completely filling either way just to support all the planned units.

Sorry I should have mentioned insulation, obviously i'd apply some insulation prior to creating the slab above a layer of DPC. My plan would be pretty much this

The most annoying thing about insulating the existing joists, is taking up the current boards, they are old treated and varnished oak boards that are nailed in and I think i'll end up damaging and replacing them. I could possible do it in the summer when its dry and just take up the boards I fixed from the rot, crawl under and attempt to do it without taking them all up.

 

[MartinB85]

Building Control would not permit you to do any compacted layers beyond about 600mm as they will drop.

In this case I guess I could at least attempt to even out the underneath to the maximum depth I could go and get some dpc slab down to try and help the standing water, or I just get dirty and try insulate the joists instead when its dry under there and then look to try and stop the water penetration from the outside (probably a much cheaper job!)