Under wooden floor is concrete

[Ginge_87]

Ground floor living room has wooden floor boards on lifting them I have found that the joist are in the concert and the concrete has black asphalt on top.1920s house
is this right and ok? also on the one picture i have metal which needs changing as a patch for the floor can i concrete this in?

 

[PaintersWillSortIt]

Ground floor living room has wooden floor boards on lifting them I have found that the joist are in the concert and the concrete has black asphalt on top.1920s house
is this right and ok? also on the one picture i have metal which needs changing as a patch for the floor can i concrete this in?
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The “joists” are screeding bars that would have been there to help level the floor, they usually are taken out as one goes along.
The tar is a how they used to seal things, asbestos bitumen is a thing but I’m not sure if your floor necessarily has it.

 

[Ginge_87]

The “joists” are screeding bars that would have been there to help level the floor, they usually are taken out as one goes along.
The tar is a how they used to seal things, asbestos bitumen is a thing but I’m not sure if your floor necessarily has it.

the floor boards are nailed to the joists, i have never seen anything like this before why put a wooden floor down just finish the concrete.
can i fill the last picture with concrete as the metal capping is weak?

 

[PaintersWillSortIt]

the floor boards are nailed to the joists, i have never seen anything like this before why put a wooden floor down just finish the concrete.
can i fill the last picture with concrete as the metal capping is weak?

Something that I didn’t think about is the possibility that the original cavity below the ground floor was filled with concrete. Are there air bricks on the external wall below the level of the floor boards?

 

[Mark's Dad]

the floor boards are nailed to the joists, i have never seen anything like this before why put a wooden floor down just finish the concrete.
can i fill the last picture with concrete as the metal capping is weak?

This is the second one of these that's been posted on here in the last few weeks or so. Last one thought his floor boards were fixed to joists in a concrete floor. Turned out they weren't joists but battens which I'm sure he cut through and ripped them out as the floor boards where stained, damp and going rotten and filled the gaps left with concrete, he might have put down liquid DPM afterwards too. This is perhaps another example of the same shoddy practice.
I would see how deep you can drill down into your "joists" you will likely find they're just battens.

 

[Ginge_87]

Something that I didn’t think about is the possibility that the original cavity below the ground floor was filled with concrete. Are there air bricks on the external wall below the level of the floor boards?

no air bricks

 

[Ginge_87]

This is the second one of these that's been posted on here in the last few weeks or so. Last one thought his floor boards were fixed to joists in a concrete floor. Turned out they weren't joists but battens which I'm sure he cut through and ripped them out as the floor boards where stained, damp and going rotten and filled the gaps left with concrete, he might have put down liquid DPM afterwards too. This is perhaps another example of the same shoddy practice.
I would see how deep you can drill down into your "joists" you will likely find they're just battens.

The floor joist are normal size and still strong, its like tar has been poured on them

 

[Mark's Dad]

Are you sure they are in fact joist's? The other poster thought they were , even his damp surveyor thought they were, and he suggested they needed to be removed. Those also looked like full joists until he drilled one of them and found they were only 5cm deep. Timber sat in old concrete isn't a good thing. A cheap damp tester will tell if the timber has too much moisture.
The tar you refer to will be bitumen and like "Painters" has said it may contain asbestos. You can get DIY kits to test for asbestos from Amazon and B&Q amongst other places.

 

[Mark's Dad]

Have checked back and found the other post from 1st October this year, take a look at this post, link below, very similar to what's in your pictures Ginge:-

M

Post in thread 'Damp Timber Joists within concrete floor - HELP'

Oct 1, 2024

Ah right! So looks like they're arent really floor joists then, thats handy. Would think thayd laid 2in x 2in battens on top of the concrete so it's easy to fix wooden floor boards down on top.
I'd have them all up if they're all the same and clean up properly just in case there's any rot started and fill the channels with concrete. Very strange but I could see why it was done for relaying a timber floor down.
The damp company would have seen what we all saw and presume they're full joists they'd have had no idea what was beneath.

• Mark's Dad

 

[Ginge_87]

Are you sure they are in fact joist's? The other poster thought they were , even his damp surveyor thought they were, and he suggested they needed to be removed. Those also looked like full joists until he drilled one of them and found they were only 5cm deep. Timber sat in old concrete isn't a good thing. A cheap damp tester will tell if the timber has too much moisture.
The tar you refer to will be bitumen and like "Painters" has said it may contain asbestos. You can get DIY kits to test for asbestos from Amazon and B&Q amongst other places.

Just seen other post thanks for sharing, very similar the wood is more than 50mm mor like 60. And very must sold still

 

[Mark's Dad]

Glad to read that in at least your case the timber is stiil dry and solid. Having said that 6cm is not really a joist. Inclined to think the "Painters" may be right in that the timber was there originally to get the floor leavels right for the concrete floor and left in place as a good fixing to nail the floor boards down. Just thinking, if those are 6cm deep then looks like they aren't more than 2cm in width. So long as you have no sign of damp I'd just make good and reboard once that's cured.

 

[Ginge_87]

Can’t see it’s just that I think your right it’s just done for show maybe as so many joists just a weird way to do a floor but still strong 100 years later. How should I go about filling this think a wall was there for living room and dining room once upon a time. Then for some reason used a metal lid which is weak

 

[Mark's Dad]

I'm not sure about the metal plate, looks a lot like it may be an old piece of zinc flashing thats been used to cover over a hole in the floor, doubt it's lead as it would be too soft.
Any idea if the old wall originally ran under the new wall?
What's on the otherside of the wall?
What's in the void beneath the plate and whats the blue foam doing in there?
Wondering if it done like that as a way to install or access central heating pipes run under the floor level.
I'd check how deep the void is and how far back it goes and be inclined to remove the plate and fill the hole with a small amount of concrete depending on what you find.

 

[Ginge_87]

I'm not sure about the metal plate, looks a lot like it may be an old piece of zinc flashing thats been used to cover over a hole in the floor, doubt it's lead as it would be too soft.
Any idea if the old wall originally ran under the new wall?
What's on the otherside of the wall?
What's in the void beneath the plate and whats the blue foam doing in there?
Wondering if it done like that as a way to install or access central heating pipes run under the floor level.
I'd check how deep the void is and how far back it goes and be inclined to remove the plate and fill the hole with a small amount of concrete depending on what you find.

Its just a thin metal which has been nailed down, i think the wall which use to separate living room and dinning this has gone and they have put chipboard flooring down in its place but have left this.
underneath is a small void say 15mm and then concrete i was thinking of just cement and SBR which has a waterproofing in it so it keeps damp out?

 

[Mark's Dad]

Filling that hole up using an SBR mix sounds fine I think from what you're saying but don't just use cement you really need sharp sand in the mix! Cement alone will crack and break up, imagine it's just an adhesive that binds bigger particles together. At least 3 or 4 sharp sand to 1 of cement. Builders/soft sand isn't ideal really but you could get away with it as it's such a small area. Follow the SBR mixing instructions but I would tend to put in a little less than they say with that.