After scouring this forum avidly for information, I'm posting up for the first time in the hope of some useful info. To be honest, I'm really hoping for a response from Mattysupra as he seems to be The Man when it comes to this sort of problem!
OK, room is 30m2 and I want to lay oak wood-block parquet (which I've already bought). House is 1950s.
I lifted the carpets to find it had been very badly 'levelled' with chipboard. This was screwed to the concrete floor underneath, also stuck down with loads of stinky bitumen. The floor screed was very poor - like the bl**dy Himalayas!
The room was originally 2 rooms (before we bought the house). In the front half, the screed sounded very hollow and had a number of cracks in it. I used a wrecking bar to lift it (complete with bitumen) off the concrete slab underneath. Easy, as it had been laid over dry 5mm gravel so was effectively unbonded (some sort of primitive damp proofing attempt?) The slab underneath is very uneven, but apparently sound (no cracks, sounds good and thick). No evidence of a DPM though. The old screed that I removed was about 30 - 50mm thick (varied).
In the back half of the room, tapping the floor in different places suggests that the screed (again very uneven) is bonded to the concrete underneath much better (except where an old fireplace was - I have not investigated this yet - looks as if it could be a bit damp there too). The screed in the back half has 3 wooden battens in it running the length of the room (to make screeding 'bays'?).
I hired a flail machine and took off much of the bitumen in the back half (fun job), although some stubborn bits and some staining do remain.
One thing that concerns me is that, while the top of the concrete slab (as now visible in the front half) sits at DPC level (which can be seen in the inner leaf of the wall), the screed in the back half of the room is currently above it. As it's a bonded screed with (almost certainly) no DPM, it's effectively bridging the DPC, although there's not currently any evidence of damp in the walls.
Anyway, I'm currently thinking that the front half of the room should get 2 coats of aqueous bitumen liquid DPM (eg syntheprufe) onto the slab, second coat sand blinded, followed by a 50mm semi-dry SBR modified sand and cement screed (maybe with polyprop fibres in the mix?) Does this sound OK?
Then what to do with the back??? Try and sort out what I've got and bring it to the level of the new screed with SLC over a liquid epoxy DPM? Or should I try and get the old screed off the slab in the back half of the room too, perhaps with a kango? Not a job I look forward to...
This floor is really doing my head in!
Thanks in advance for any input, sorry about the long essay!
Dom
OK, room is 30m2 and I want to lay oak wood-block parquet (which I've already bought). House is 1950s.
I lifted the carpets to find it had been very badly 'levelled' with chipboard. This was screwed to the concrete floor underneath, also stuck down with loads of stinky bitumen. The floor screed was very poor - like the bl**dy Himalayas!
The room was originally 2 rooms (before we bought the house). In the front half, the screed sounded very hollow and had a number of cracks in it. I used a wrecking bar to lift it (complete with bitumen) off the concrete slab underneath. Easy, as it had been laid over dry 5mm gravel so was effectively unbonded (some sort of primitive damp proofing attempt?) The slab underneath is very uneven, but apparently sound (no cracks, sounds good and thick). No evidence of a DPM though. The old screed that I removed was about 30 - 50mm thick (varied).
In the back half of the room, tapping the floor in different places suggests that the screed (again very uneven) is bonded to the concrete underneath much better (except where an old fireplace was - I have not investigated this yet - looks as if it could be a bit damp there too). The screed in the back half has 3 wooden battens in it running the length of the room (to make screeding 'bays'?).
I hired a flail machine and took off much of the bitumen in the back half (fun job), although some stubborn bits and some staining do remain.
One thing that concerns me is that, while the top of the concrete slab (as now visible in the front half) sits at DPC level (which can be seen in the inner leaf of the wall), the screed in the back half of the room is currently above it. As it's a bonded screed with (almost certainly) no DPM, it's effectively bridging the DPC, although there's not currently any evidence of damp in the walls.
Anyway, I'm currently thinking that the front half of the room should get 2 coats of aqueous bitumen liquid DPM (eg syntheprufe) onto the slab, second coat sand blinded, followed by a 50mm semi-dry SBR modified sand and cement screed (maybe with polyprop fibres in the mix?) Does this sound OK?
Then what to do with the back??? Try and sort out what I've got and bring it to the level of the new screed with SLC over a liquid epoxy DPM? Or should I try and get the old screed off the slab in the back half of the room too, perhaps with a kango? Not a job I look forward to...
This floor is really doing my head in!
Thanks in advance for any input, sorry about the long essay!
Dom
