Old floorboards - what is underneath?

[portuguesejohn]

Ripped out fairly old carpet from the living room and dining room of our 1930s house to find the floorboards in a much worse state than the upstairs rooms.

The boards look mostly fine in the centre of the rooms, but the edges appear to have been painted in the past, I believe this used to be called "black edging", some sort of decoration from generations ago or something...

Most of the boards feel fairly loose, I even pulled out some nails that had mostly rusted away, but I am more interested in what I found underneath the floorboards (attached as pictures).

I have also attached some pictures detailing the state of the worst sections of the floorboards, some of these I believe will need to be replaced entirely.

The floor appears to be concrete with a black substance covering the top with a lot of wear and tear, the floorboards are nailed straight into this concrete/black substance as well. It all looks dry, I couldn't really feel much in terms of moisture, here is a video demonstrating it as well:

https://imgur.com/a/qu41CY7

I am now wondering what to do about this before we decide on the new flooring. We were hoping to have some sort of "easy to take care of" vinyl of sorts, but I worry about the condition of the floor underneath the floorboards, should I have it all ripped out and retreated? With what? And what sort of tradesperson would I be looking for? I suspect the average fitter won't want much to do with this...

Thanks, (a clueless individual)...

 

[Deleted member 174758]

Painted edges ( or "black edging" as you put it) was common before fitted carpets became the norm in the 1970s. People used large carpets and the perimeter areas of the floot of the room would be polished, painted or even covered with lino

Your floor sounds like bitumen over concrete or possibly solid asphalt. The fact that the nails have rusted in places probanmbly hisn't too significant, unless they all have. It may just indicate boards which were still a bit wet when laid or that a small amount od moisture was trapped between the black stuff and the boards. Are there any signs of wet rot in any of the boards? If so the DPM in the floor is possibly breaking down and will need to be dealt with (that is more significant)

 

[portuguesejohn]

Painted edges ( or "black edging" as you put it) was common before fitted carpets became the norm in the 1970s. People used large carpets and the perimeter areas of the floot of the room would be polished, painted or even covered with lino

Your floor sounds like bitumen over concrete or possibly solid asphalt. The fact that the nails have rusted in places probanmbly hisn't too significant, unless they all have. It may just indicate boards which were still a bit wet when laid or that a small amount od moisture was trapped between the black stuff and the boards. Are there any signs of wet rot in any of the boards? If so the DPM in the floor is possibly breaking down and will need to be dealt with (that is more significant)

Hi,

Thanks for your input. I have read about what you have mentioned. The bitumen feels very smooth on touch, from a distance it looked even liquid which was quite scary... But it is actually dry to the touch, as far as I can feel in the boards I pulled up. Most of the boards in these 2 rooms feel loose here and there, and it doesn't help that they don't appear to have been properly nailed once one of the walls was taken down (open area living and dining room).

The worse affected areas are definitely to the sides of the fireplaces in both rooms, a couple of pictures attached.

It doesn't help that these "painted edges" appear to have been painted in both black and beige at different times... I'm not that good at identifying what is rot or not, and all of these discolouration doesn't aid at all.

In terms of the DPM, the bittumen/asphalt would have beens supposedly laid to act as a DPM back in the time? A lot of it seems to have glued to the floorboards, so I can't imagine it being in too good of a condition. What would be done to properly address this? Would all boards need to be pulled out and sheets of DPM laid down?

 

[Deleted member 174758]

Bitumen and asphalt would both have been used as a sort of DPM when the house was built. If bits are sticking to the back of the floorboards it sounds more like bitumen. It has a tendency to harden and crack over time, however. Looking at the photos the boards don't seem too bad and they could probably be belt sanded and reinstalled. The simplest solution is probably going to be lay some Visqueen (1000 gauge polythene DPM where the boards are going back and reinstall them rather than do the lot. In the longer term if any more damp were to show up it migjt be necessary to lift all the boards, remove the bitumen, add a DPM and rescreed, but for the small amount if damp you have i hardly think that's necessary at this stage

 

[portuguesejohn]

Bitumen and asphalt would both have been used as a sort of DPM when the house was built. If bits are sticking to the back of the floorboards it sounds more like bitumen. It has a tendency to harden and crack over time, however. Looking at the photos the boards don't seem too bad and they could probably be belt sanded and reinstalled. The simplest solution is probably going to be lay some Visqueen (1000 gauge polythene DPM where the boards are going back and reinstall them rather than do the lot. In the longer term if any more damp were to show up it migjt be necessary to lift all the boards, remove the bitumen, add a DPM and rescreed, but for the small amount if damp you have i hardly think that's necessary at this stage

Thanks again, I never noticed any damp on the walls or the skirting, we have even pulled all of the old wallpaper and had it replastered early in January... No signs of anything bad.

I did have a floor professional over today and his advice was to talk to a builder or someone who is into damp to remove all the floorboards and do a proper job before doing the new floor. He also noted that even the boards that were in a good state were "cupping", which to him indicated some moisture present.

Pardon my question here, it comes from a place of ignorance when it comes to damp, but if I was to lay down this new layer of DPM (would this go over the old bitumen?), wouldn't this just drive the damp towards other places such as walls? I suspect that if water is coming up, it must go somewhere right?

 

[portuguesejohn]

Bitumen and asphalt would both have been used as a sort of DPM when the house was built. If bits are sticking to the back of the floorboards it sounds more like bitumen. It has a tendency to harden and crack over time, however. Looking at the photos the boards don't seem too bad and they could probably be belt sanded and reinstalled. The simplest solution is probably going to be lay some Visqueen (1000 gauge polythene DPM where the boards are going back and reinstall them rather than do the lot. In the longer term if any more damp were to show up it migjt be necessary to lift all the boards, remove the bitumen, add a DPM and rescreed, but for the small amount if damp you have i hardly think that's necessary at this stage

Another question: If the boards are to go above the DPM, would I still want to nail them through the DPM? I assume this would create various weakness points, is this just something one has to live with?

 

[JohnD]

1930's concrete is usually poor quality.

I wouldn't rely on nails into it.

 

[portuguesejohn]

1930's concrete is usually poor quality.

I wouldn't rely on nails into it.

What would be the best approach to fix the boards in place?

 

[JohnD]

what is the height difference between the subfloor concrete, and the boards?

Are there any airbricks into the gap?

Is the concrete weak enough to scratch with a teaspoon, and is it damp?

I'm thinking of either a floating floor, or dig it out

(or both)

especially if an old water pipe runs under it.

 

[portuguesejohn]

what is the height difference between the subfloor concrete, and the boards?

Are there any airbricks into the gap?

Is the concrete weak enough to scratch with a teaspoon, and is it damp?

I'm thinking of either a floating floor, or dig it out

(or both)

especially if an old water pipe runs under it.

The layer of bitumen appears to be around 3-4mm, some sections seem pretty flat, other have detached and glued to the floorboards.

Surface of the concrete is fairly dusty (can be seen in the video of the original post). Concrete itself feels solid, can't really scratch at it with a teaspoon, nothing feels wet or damp, nor have we seen any signs of rising damp in the walls (they were wallpapered stripped and replastered/skimmed).

Building contact assessed the photos and said he would just replace the bad boards and sand/fix the rest, but I am having it looked at by a few others in the days. Digging it all out would be difficult as we still need to live here and it would cause all sorts of aggro, not to mention what I imagine a much bigger cost (even if it is the absolute best solution...).

 

[Deleted member 174758]

I'd certainly consider sealing any bare concrete with a D4 PVA glue (e.g. EverBuild D4 Wood Adhesive from Toolstation - avoid anything called D4 that foams) and sand blinding it with sharp sand whilst it is still wet. That will seal the concrete and reduce the dust as well as being relatively damp proof. The sharp sand provides a mechanicsl key for any filler. Once set I'd sweep up the excess sand and fill the hollows with a cheap cement based filler. Your replacement boards can then be glued down with a parquettype adhesive such as Lecol 5500.

TBH, though, a Visqueen DPM and secret skew nailing into the concrete with masonry nails (pre-pilot the nail holes through the grooved at the edges of the boards with a small drill bit) will br perfectly adequate.

 

[portuguesejohn]

Damp company came around and did a survey. Really informative guy that appears to know what he is talking about, no cowboy techniques that I have read about the damp industry. Used the common "protimeter" but did state it should only be used on wood (good), the only section of the boards in which the meter pointed up was near the fireplaces, which made sense. The rest of the boards appear to be fine, especially considering the age of the property. Guy effectively said this wasn't really an issue and gave following options:

* Live with it. Situation is not as bad I thought it was.
* Replace the boards around the fireplaces/hearth as some of them are starting to show initial signs of rot, especially around the old nail holes that have rusted. Sand the rest.
* Have it all pulled out, including the skirting, and install a DPM layer (liquid based), this would fix it for the long run. (waiting on quote)

Considering the guy was clear about this not really being an issue, I'm leaning towards option 2, which leaves me with a few questions:
* What type of floorboards to replace around the fireplaces with? The guy did say most of the stuff you can get on the big stores like Wickes and the likes is much inferior in quality to what I currently have.
* Do I even want floorboards? Any other subfloor with vapor resistance would be fine as long as we could level it with the rest of the floorboards and have it ready for the finish (vinyl).