Edwardian house, flooring surprise - not a good one !!!

[ianleon]

Having started work on one of the many rooms that need renovating in our newly purchased Edwardian house, I thought i'd start with re-wiring assuming I would be faced with a floating floor, making my life easier. On lifting the first few boards, carefully as the boss wants them instead of carpet I was surprised to see they are laid on concrete (not sure if this was done from the build in 1905) Anyway what I have now found is that the floor is covered with what looks to be bitumen which has broken down in areas and caused mould and damp to set into the underneath of the boards.
My question would be how is best to fix this ?
How would I know the concrete slab is all ok, correct depth, etc ?

 

[Deleted member 174758]

Concrete was used with increasing frequency from the 1890s onwards (most notably in the Glennanfinnan viaduct - the one the West Highland line, as used in the Harry Potter films, built 1897 to 1899) although the quality found in Victorian and Edwardian buildings is often truly horrendous. So your house date is potentially correct for original use of concrete.

This early concrete was pretty much always mass concrete, that is without any re-inforcement, and whilst it is strong in compression it is relatively weak in tension. Like all concrete it continually cures and is liable to crack throughout its' lifetime but without rebar it can fail quite easily. Another problem is that concrete from that period simply doesn't have any DPM beneath it as the materials we use today just didn't appear until after WWII, so where these old buildings have concrete floors they may well have a thin top coating of bitumen or tar (often from the local gasworks) over the top of the concrete to fulfill the same function as a DPM. This often deteriorates and/or cracks or flakes with age and/or curing of the concrete. In those early days of modern concrete use they not only didn't use steel re-inforcement, but the concrete was slso generally pretty thin by today's standards as well.

So, personally, I'd seriously consider digging it all out and putting in a proper rebar-reinforced concrete floor with a proper DPM below it because it cant really be "fixed" as such

Sorry about the history lesson, but I thought I'd try to explain the logic behind my advice

 

[johnny2007]

If floor height is not a problem, dpm, then 4 inches reinforced concrete on top.
But I guess you're not going to fancy a step in your house...

 

[bobasd]

pull those proud nails before anything else.

knock off plaster and clean the brickwork up to about 600mm to 700mm from the floor.
totally remove all wallpaper.
there has been a previous chemical DPC judging by the injection holes in course three.
whats the conditions on the other sides of the walls?

dig the floor out to the soil surface, & then come back with pics of what you've done showing the FFL of adjacent rooms.

if the boards are definitely nail free you could run a planer up them to remove all fungus and adhesive - they are probably good wood, & the backs could be treated after cleaning up.

 

[foxhole]

Looks like fairly new t&g board’s, Edwardian properties I have worked in all had wide square edged pine floorboards.

 

[Deleted member 174758]

Looks like fairly new t&g board’s, Edwardian properties I have worked in all had wide square edged pine floorboards.

Not always. I tend to associate really wide square edges floor boards more with Georgian houses, i.e pre-1837. Four-speed match planers were in common use in larger towns and cities in the UK by the 1860s (a number of models were exhibited at the 1851 exposition). I've seen a number of original machined t&g floors on buildings as early as the mid-1850s (we are currently working on an entire mill complex floored out with t&g, with the earliest building dating from 1830 and all the original floors intact so far as the conservation officer can ascertain)

 

[ianleon]

Wow, thank you so much for the replies, i feel like i've learnt quite a lot already.

All wall paper is off and as there was wood panelling 1/4 way up the wall we removed that as we could feel it was loose and the plaster just fell off !

It has cavity walls and the DPC looks ok from the outside.

The holes you can see in the picture were where the rad was, there is no further sign of injection.

The floor boards where only T & G when I got to the area near the window.

A few follow up questions:

If I use the products on the market to level off and paint a DPC on could this effect it structurally in the future ?

If digging up is the best way forward its something we will do as its the forever home, is it a case of going all the way down to soil and hardcore, then concrete do i need to put any insulation boards down ?

Would I also be best to inject a DPC into the internal walls and if so at what height ?

This is room one of six on the ground floor and as this is likely to be the same all over the house am I ok to do one room at a time ?

Thanks in advance.

 

[ianleon]

Also, what about the fire place, would should I expect under that ?

 

[bobasd]

OP,
i made a few observations and suggestions above.
fwiw: do you intend to carry any of them out?

 

[Deleted member 174758]

Also, what about the fire place, would should I expect under that ?

Often times I've found have either a stone slab or a cast concrete one atop thin floorboards laid over joists. Top surface is level with the surrounding floorboards. On ground floors may be slightly different with stone or concrete atop brick piers etc

 

[Deleted member 174758]

It has cavity walls and the DPC looks ok from the outside

Cavity walls started appearing in the 1870s around here (a "stone" district where it must have been cheaper to have a brick inner skin). My own house is 1881 and has a full cavity walls despite being a terrace property. Main problem that ive seen with these early cavity walls is where careless brickies have dropped waste/excess mortar down the cavity. This can cause cold bridging and/or damp ingress near the base of the walls in some cases. One "cure" in the 1970s and 1980s was to inject chemical DPC at 150 or 200mm or so centres somewhere near floor level indoors with the holes angled downwards. Outer skin drilled to match. TBH this is a job you can do yourself (just hire an injection pump and buy the paraffin like injection DPC compound) but this type of DDPC does tend to break down before the 25 year mark of most guarantees and needs to be redone periodically (from personal experience on two houses, now and the experiences of others I know). Note that when doing this job it is necessary to chop away the bottom 600mm or so of plaster and the skirting to expose the brick, then replaster after you've injected. Also note that ideally you should replace the stripped out plaster work like for like (I.e. with lime plaster, not gypsum plaster), although a friend of mine actually redid the bottoms of his walls (Edwardian fireman house) in cement based render up to the mid wall level and managed the joint by fitting a period timber dado rail round the reception rooms on the ground floor. The render isn't as smooth as plaster, but he has decorated with traditional heavy papers so the difference isn't visible at all. Mind you, his house is in a flood risk area and this approach means that after a flood (three times now) he can get the house dried out far faster than if the walls were all plastered

If I use the products on the market to level off and paint a DPC on could this effect it structurally in the future ?

The problem with bitumen or tar is that you cant get most materials to adhere to them. They also attack a lot of conventional DPM products. If you don't want to fig out and replace it will be necessary to at least scabble or grind the surface to remove all the black stuff before sealing it with something like an epoxy DPM as opposed to a one pack paint on solution. If you go the whole jog and dig it out then defo use some form of insulation in the floor such as those baked ceramic "marbles" (added to the concrete mix) or a 50 to 100mm layer of cellular insulation between the concrete and the finishing screed

This is room one of six on the ground floor and as this is likely to be the same all over the house am I ok to do one room at a time ?

I think so, yes

 

[ianleon]

OP,
i made a few observations and suggestions above.
fwiw: do you intend to carry any of them out?

Yes I do, thanks for the suggestions. (is it bad i had to google what FWIW meant !)

Currently on shift until Tuesday when I then plan to completely empty the room and get the rest of the boards up and see what i'm up against.

 

[ianleon]

@JobAndKnock

If I were to either dig out and re-concrete with proper DPM or manage to get off all the bitumen and use the epoxy stuff, inject the internal and external wall with the chemical DPC would a lime plaster still be necessary ? The wife ideally wants a smooth finished wall with just paint (the whole house is currently wall papered). We are thankfully not in a flood risk area.

 

[ianleon]

Well a little update and a few more questions !
Managed to get all the boards up and all cleaned - What a job that was.
And now i'm left with this:

There was a weird square in the centre with a hole in:

So chipped off the bitumen and it was all cracking up underneath so kept tapping away, it looks to me as if it has possibly been a floor repair at some point but not sure what the pipe that was in there was all about:

Any way I have chipped away at some of the other bitumen areas and it appears to me that all the black stuff is mixed in with the concrete and stone and not just a painted top coat (not sure how they used to do it back in those days)

So i'm curious to where this leaves me now and if the only option is to gun up the whole floor and start afresh ?
I have spoken to a number of flooring products specialists (sika,Ardex and Permaguard) and as above the bitumen needs to be removed before any of the products will work correctly but i'm not sure that is possible with what I have ?

 

[johnny2007]

Raising the floor by 2 inches an option?
If so, you could use a dpm and then concrete over and finish as you would normally do