Concrete Slab or Suspended Timber Floor ?

dagda88

Hi All!

Having done the research on the pro's and con's and advice from builders with differing opinion I am still in the dark. Hoping to get some sound advice and put this to bed so I can move along with the project. I'm doing the most of the work myself.

Here's the situation:

3 Bed Mid Terrace, late Victorian/Edwardian build, roughly 1900-1920's

There have obviously been many different builders and works carried out on the property over the years. Having been re-wired and re-plumbed in recent years they seem to have avoided the floors and worked around it, rather than fixing it.

Having identified a case of dry/wet rot in the ground floor, the ground floor has come up and presented the following:

1)The hallway covered in laminate revealed a completely rotten suspended timber floor, which seems to have been bodged onto bricks, railway sleepers and bits of window frames, just resting on the ground.

2)The front room covered in carpet (no underlay) revealed a suspended timber floor consisting of MDF, floorboards, chipboard etc. Joists resting on very shallow sleeper walls with soil touching timber. The room also had an old cast iron vent at the front blocked with mortar mix.

3)The back room again a bodged timber floor, revealed a (badly) poured concrete floor with joists in situ. Having removed the concrete and rotten joists, a vent (hole) connecting front to rear was found, however none to the rear of the house.

4)Having gone this far the kitchen might as well be done, however this is lino covering old red victorian quarry tile in poor condition and I'm unsure what to do with this.

I have dug out all rooms apart from kitchen and removed a meter of plaster from all walls.

This also revealed the party walls for both rooms adjoining the hallway are brick with bonding timbers vertically (partially rotten) and timber sole plates (rotten/non-existant).

So I've been advised:

A) Concrete slab, insulation, waterproof plaster etc etc. Pack dry mortar mix in to replace rotten sole plates and either replace bonding timbers or again mortar mix.

Suspended timber floor, open up new air vents, insulate between joists etc etc. Back to the original breathable structure of the building.

My issue is that concrete might force damp up the walls and or jeopardise the buildings ability to breathe thus creating more issues, also how to support party walls in hallway can concrete be poured underneath?

Whereas a timber floor, vents will have to be opened up, possibly lowering external ground heights and over time prone to rotting.

What are people's thoughts on the matter, I know plenty of houses have had a concrete slab put in after the fact and have been fine but still concerned is it worth it?

dagda88

Also, having removed plaster I noticed holes spaced equally around all the ground floor walls which I'm guessing means they injected the walls but didn't actually solve the root cause of the problem.

BryanF

Have you considered a breathable floor build up? Radon sump then leca with lime on top? Renovation in a 60's house at the moment and just going with felt draped between joists, insulation between and vapour barrier/air-tightness on top

BryanF

dagda88 wrote: »

Also, having removed plaster I noticed holes spaced equally around all the ground floor walls which I'm guessing means they injected the walls but didn't actually solve the root cause of the problem.

Not a fan of injection, prefer electro osmosis

dagda88

BryanF wrote: »

Have you considered a breathable floor build up? Radon sump then leca with lime on top?

Never heard of this method before, just had a look at it there. It does seem to have the qualities that I would want in terms of breathability, but is this overkill?

If I re-instated the timber floor

BryanF wrote: »

with felt draped between joists, insulation between and vapour barrier/air-tightness on top

and improved ventilation throughout the subfloor would this not do the trick?

The builder that recommended the concrete floor also recommended the electro osmosis method saying that "it seems to work, he doesn't know why or how" but it does. Reading into it, there doesn't seem to be any scientific evidence that it does anything?

BryanF

dagda88 wrote: »

Never heard of this method before, just had a look at it there. It does seem to have the qualities that I would want in terms of breathability,
1: but is this overkill?

2: If I re-instated the timber floor and improved ventilation throughout the subfloor would this not do the trick?

The builder that recommended the concrete floor also recommended the electro osmosis method saying that "it seems to work, he doesn't know why or how" but it does. Reading into it,
3: there doesn't seem to be any scientific evidence that it does anything?

1: No
2: Yes
3: it does. There is plenty of science.

dagda88

It depends on it's use, it seems like it may be overkill for me right now, but then again I don't know much about it. Any more info on it?

So suspended timber with the insulation would work then, what's your opinion on the concrete slab then? Am I right in saying it's not the best option and may cause problems?

Whatever about the electro-osmosis but from what I've read, that's what's being said....