Damp Timber Joists between concrete - HELP

[christian777]

Lifted up the old laminate and found moisture underneath, mostly where the nails where within the floorboards.

Having got a damp proofing company round, they detected moisture within the floorboards and suggested the joists where the issue because they were in-between concrete and it was evident from the rusty nails. It looks like previously the potential suspended floor joists where filled with concrete now it looks like as per the picture (there not blocks)

Recommendation was to remove joists, fill with concrete, then self level and finally cover with liquid DPM

Question was - I was planning to remove some of the rotten joists and leave the ones which are intact, although prob do have moisture. Do I go with removing the joists or can I just put self leveling over the top? If the answer is remove them, what's the best and quickest way to do this? My main comcern is if i dont remove them will it comprimise the damp proofing in the future (if joists rot leading to the floor/DP cracking)

 

[ree]

OP,
You need to remove all the joists.
Is this in one room only or throughout the GF of the house?
What condition are the floorboards & skirtings in?
Is there a space below the floor or does the floor we can see actually sit on the soil? ie. a solid floor?
Do you have any air bricks around the house?
Do you have damp in the walls?

 

[christian777]

OP,
You need to remove all the joists.
Is this in one room only or throughout the GF of the house?
What condition are the floorboards & skirtings in?
Is there a space below the floor or does the floor we can see actually sit on the soil? ie. a solid floor?
Do you have any air bricks around the house?
Do you have damp in the walls?

Thanks for responding.
It's throughout the ground floor.
Floorboards were OK, but there was moisture detected.
Not sure whats underneath the joists / concrete
There are no air bricks around the house
The walls are OK except one where we had an old fire place. I believe it's the salts
Also most of the timbers are intact just a few which have rotted

 

[JohnD]

When old timber floors are filled in with concrete, it is usually because there is a damp problem.

Very annoyingly, the cause of damp itself is usually not cured, so the damp continues, and it is much harder and more expensive to repair the leaking pipe or mend the broken drain when concrete has been poured on top of it.

 

[ree]

OP,
Do the timbers go into pockets in the walls?
Best practice would be to remove all the timbers from all the ground floors - the hidden part of the timbers might be rotting out of sight?
The worst case conditions would be for Dry Rot to start. At the moment you presumably only have wet rot?

However, only remove them in the room in question if removing them in all the rooms is going to cause too much disruption - afterwards you can only wait & see what, if anything, happens next? Your call?
It seems like the concrete has been poured on the soil without using a DPM, & moisture is creeping up through the concrete - & penetrating maybe from the outside walls?

Spraying with woodrot chemical & filling the gaps left after timber removal, and spreading a liquid DPM could be done by yourselves.

 

[dazlight]

We had a few of them type sub floors asphalted. We filled in the voids were the timber was with ardex na and a46 rapid and then got a 20mm of flooring grade asphalt. Very popular in the north west.

 

[christian777]

Thanks for responses having ripped up all the floorboards. The joists seem pretty OK. I think most of the moisture came from the concrete when Initially pouring it in. I think I should be OK with a dehumidifier for couple days and another layer of dpm