Insulating a floating floor?

mollzer

Have recently bought an old house and it has floor boards over what appears to be 2 foot of fresh air underneath!
I have never come across this type of floor before but was wondering if anyone here has, and is there any way of insulating it ?

And preventing hoards of vermin taking up residence underneath our floorboards?
Would feel alot more secure knowing this space is not there.

gsxr1

mollzer wrote: »

Have recently bought an old house and it has floor boards over what appears to be 2 foot of fresh air underneath!
I have never come across this type of floor before but was wondering if anyone here has, and is there any way of insulating it ?

And preventing hoards of vermin taking up residence underneath our floorboards?
Would feel alot more secure knowing this space is not there.

I think this void is part of the house ventilation system. I dont think is should be filled, but can be insulated with vents installed into the room

mollzer

gsxr1 wrote: »

I think this void is part of the house ventilation system. I dont think is should be filled, but can be insulated with vents installed into the room

Ok, that sounds reasonable. But the previous owners have most of the rooms covered with laminate flooring, covering the old wooden flooring, with no vents in any of the rooms.
We have wall air vents on our list of 'to dos' in the New Year.

But is 2 foot normal for an underfloor ventilation system? this is the first time I have come seen this.

Poor Uncle Tom

What you describe is fairly common in council built houses from the 1930's. The floors are ventilated via vent bricks in the wall below floor level. The ground was usually left as subsoil and coated in burned lime.

The usual methods of dealing with this type of floor is to remove the floor boards, secure chicken wite to the underside of the joists and fit quilt insulation between the joists and fit back the floorboards.

The preferred option of dealing with this floor is to remove the timber floor altogether and replace with a conventional concrete floor construction incorporating insulation, damp proofing, radon barrier and perimeter insulation to stop cold bridging.

gsxr1

Poor Uncle Tom wrote: »

What you describe is fairly common in council built houses from the 1930's. The floors are ventilated via vent bricks in the wall below floor level. The ground was usually left as subsoil and coated in burned lime.

The usual methods of dealing with this type of floor is to remove the floor boards, secure chicken wite to the underside of the joists and fit quilt insulation between the joists and fit back the floorboards.

The preferred option of dealing with this floor is to remove the timber floor altogether and replace with a conventional concrete floor construction incorporating insulation, damp proofing, radon barrier and perimeter insulation to stop cold bridging.

Why did they build them like this?
Seem like a very elaborate means of ventilation when a 4" hole in the wall would do the same thing.

Poor Uncle Tom

The ventilation was to stop the timber floors rotting, not ventilation for the living space. This was done as there was no easy means of damp proofing the floors, so this elabourite means of lifting the floor off the ground was devised using a system of joists and dwarf walls incorporating a poured pitch DPC in the walls and under the dwarf wall plates. It was a good system really.

mollzer

Poor Uncle Tom wrote: »

What you describe is fairly common in council built houses from the 1930's. The floors are ventilated via vent bricks in the wall below floor level. The ground was usually left as subsoil and coated in burned lime.

The usual methods of dealing with this type of floor is to remove the floor boards, secure chicken wite to the underside of the joists and fit quilt insulation between the joists and fit back the floorboards.

The preferred option of dealing with this floor is to remove the timber floor altogether and replace with a conventional concrete floor construction incorporating insulation, damp proofing, radon barrier and perimeter insulation to stop cold bridging.

I dont know what the actual age of the house is but do know it was a council built one, pre 1965.

The 'preferred option' sounds very expensive, 2 foot of concrete would cost alot.
Cant believe our surveyor didnt point this out to us before we purchased.

So I wonder what the disadvantages are of leaving well enough alone? or even just add new flooring over the existing wooden floors? or even tiling?

Poor Uncle Tom

We are really only speculating here as we don't know for sure that this is the way your house is done, but assuming this is the case you will not fill the full void with concrete. You start with hardcore (804 fill) blind with sand, whack and compact this and apply Radon/DPM layer, Rigid floor insulation and finally the reinforced concrete. The concrete layer itself would be 150mm thick.

rayjdav

mollzer wrote: »

Cant believe our surveyor didnt point this out to us before we purchased.?

Was it covered up before you bought or in a state ready for repair??

mollzer wrote: »

So I wonder what the disadvantages are of leaving well enough alone? or even just add new flooring over the existing wooden floors? or even tiling?

Very similar to the job I have completed on my own place. Old "cottage Acre" dwelling. Ripped out floor boards, 2' of void. As Poor Uncle Tom said is by far the best way to go, cheapest all round. Also, at least you will know this way that you will have a good level of insulation in the floor, as with the rest of my rebuild, there was nothing.

Also, dont know if you have attacked the walls yet, but be ready.:eek: If the same type of cottage as me, you are in for some surprise. Home made 9"x9"x20" solid conc block, held together with a prayer. €€€€€€€ is all I saw at first, but, like everything else, there was a solution after a lot of research.

mollzer

Thanks for the replies!
rayjdav the walls have already been dry lined by the previous owners and the attic done as well, just whats under us left.
Do you mind me asking you did it cost you much per sq ft to fix?

rayjdav

mollzer wrote: »

Thanks for the replies!
rayjdav the walls have already been dry lined by the previous owners and the attic done as well, just whats under us left.
Do you mind me asking you did it cost you much per sq ft to fix?

Mozzler,
My walls had been "drylined" too by previous owners. It was akin to the 1/2 inch styrofoam that you get on stereos. USELESS in a word. See if you can guage what is on the walls and if not good enough, I'd advise rip out and change it. I know more €€ but think about it, whats the point in ripping out a floor and making good to current standards, ditto for attic insulation, if all the heat is going to escape through the walls?:eek:

You only get one chance at this so if I were you, I'd do it now and be done.

Never actually did a calculation re the cost/sqft on it alone as I did this work integrated with a big extension on the side of the old house. Old house works consisted of ripping out floor and installing conc floors as per PUT spec above basically, drylining with insulated slabs and quilt insulation to standard in attic. Different house and costs far less to heat.