Found builders rubble under wooden floor

paddylonglegs

Folks,

As the title says,found rubble right up to the joists. Floors look like they were layed around 1920s or 30s so I expect they were too tight to get a skip (if they even existed then). I hope this is the case and its not acting as any kind of support. It's my understanding that this void under the floor should be kept clear to allow for ventilation and stop moisture rising up to living area. There is no dpc in this house. Should I be looking at removing this? Depending on the depth, were prob looking at about 5 ton of rubble here

Sam Kade

paddylonglegs wrote: »

Folks,

As the title says,found rubble right up to the joists. Floors look like they were layed around 1920s or 30s so I expect they were too tight to get a skip (if they even existed then). I hope this is the case and its not acting as any kind of support. It's my understanding that this void under the floor should be kept clear to allow for ventilation and stop moisture rising up to living area. There is no dpc in this house. Should I be looking at removing this? Depending on the depth, were prob looking at about 5 ton of rubble here

The only skip back then was done with a rope.

paddy147

Sam Kade wrote: »

The only skip back then was done with a rope.

or a horse and cart.

Odelay

tbh I'b be surprised not to find it there in a house of that age, is it right up to the top of the floor boards? Otherwise I couldn't see a need to remove it.

looksee

Are the joists actually resting on the rubble? Are there any support 'walls' under the joists?

We took up a floor (in a 60s house) with a deep void of about 24 inches and while the joists were (supposed to be) resting on block supports the space between had a lot of rubble in. The floor was very bouncy and it turned out some of the joists had warped. The guys took out the joists, built up the support walls and cleared all the rubble out down to the fairly decent concrete. They then put in new joists and floor, and it no longer bounces. The rubble didn't really matter tbh, but the guy doing it was fussy - and he had given us a price, so we were happy!

Dwork

Dig it out, create stub walls, DPC them, lay new joists and bang down a new floor. A lot of older floors were done the way yours were. They weren't big into damp-proofing.

whizbang

Floors look like they were layed around 1920s

if it ain't broke , don't fix it.

paddylonglegs

whizbang wrote: »

if it ain't broke , don't fix it.

Well it may be helping to break it. An article I recently read cites builders rubble in floor voids can contribute to damp rising up to walls in living areas. I have found efflorescence at the base of the walls suggesting a possibility of damp.

I don't think the joists are resting on rubble, but to make it easier to remove it, I may need to remove joists anyway.

jack of all

You've a number of options here, as I see it:

1. If money is tight leave well enough alone!

2. Remove boarding and joists, dig down into fill and see what depth is there, is there a concrete sub floor beneath the filling? If the quality of the fill is poor (lots of fines, wood waste or organic matter) it would be a better job to remove the lot and excavate the top 4- 6" of the topsoil below. Now, depending on depth it may make sense to go for a new concrete (ground bearing) floor slab, on compacted hardcore with proper DPM and this also allows you to incorporate some decent rigid insulation while your at it. In going this route be sure that this would not compromise cross ventilation to any adjacent suspended floors. If this proves to be the case it may be possible to incorporate some 4 or 6" ducts to maintain the required ventialtion (placing these in the blinded hardcore, below the DPM/ radon barrier). Incorporate some 1/2" flow and return pipework in lagging in the floor for future use.

3. If you decide to stick with a suspended timber floor (unusual enough nowadays), excavate down and remove all old fill and topsoil as before. Lay a 125mm (5" minimum) concrete sub floor, the finished level of this should not be below the lowest external ground level to avoid turning the floor into a sump! Build tassel walls (honeycombed to allow ventilation), top off with DPC and sole plates, treated with a brush on preservative. Make sure existing ventilation si sufficient, no harm to add additional vents. Fit new joists, with solid bridging. Drape between the joists with a breathable membrane or similar before filling the voids with a quality rigid or fibre insulation batt. Incorporate any plumbing or electrical first fix as you go. Top off with the floor finish of your choice (hardwood secret nail direct to joists or maybe fixed to a ply of OSB subfloor. Going with a sheet material sub floor allows you to store finish floor in the room for a couple of weeks before fixing, allowing the wood to acclimatize and minimize shrinkage, although there will be some movement which is unavoidable.

4. There are proprietary block and beam systems available but these are unlikely to be feasible for retrofit due to issues with access and handling.

NobodyImportant

DO NOT PUT IN A CONCRETE FLOOR WHERE THERE ARE WALLS NEARBY WITHOUT DPC's.

It will force water up the walls and will create a damp problem. Its been documented and i have a book on damp at home which even has a lovely illustration of how and why this occurs.

I have first hand experience as somebody took out our suspended floor and laid down a concrete slab over a sheet. No any damp that would have evaporated away under the sub floor, makes its way up the walls as it has nowhere else to go.

Here is somebody else explaining it - http://www.telegraph.co.uk/property/propertyadvice/jeffhowell/7949821/Home-improvements-concrete-decision.html

paddylonglegs

Absolutely brilliant replies here folks,especially jack of all, some great options layed out by you. I do agree with what nobody important says about the concrete floor though. It makes sense and I have read about this that moisture can't penetrate the concrete so finds its way outwards and up the walls.

This gives me a good direction now in what I can do

Thanks

jack of all

It is quite possible that moisture can wick up adjacent walls IF there is no dpc present in those walls. Lots of undetermined stuff here that can really only be assessed on the ground, so to speak. Water table level and nature of the soil would be a factor. I can't imagine the ventilation in the existing floor is great given how obstructed the void is by the filling. I did some work on a 1930s bungalow as a chap and DPCs were used, although they were bituminous felt and their performance had diminished over time. You'll need to open up and inspect some more before you come to a definitive solution. Good point by Nobody Important though.