DPC and level of floor screed

[dchopp]

I have removed original wooden flooring ( the finger parquet type )with the intention of laying a new oak floor. The blocks were glued down with black bitumen which has come away. The house was built approx 40 years ago.

With the floor and skirting removed I observed that the internal DPC is approximately 10-30mm above the floor screed. Why the screed was not layed to DPC level I am not able to establish. Although there is no evidence of damp in the room I believe I should take some sort of action to prevent any chance of damp getting to the wood and ruining it. My intention was to brush on coats of damp proof membrane on the floor.

I presume I could brush the membrane onto the walls also and cover the DPC so that the wood is totally enclosed around the edges. The new skirting will then cover it.

However damp is a problem area and I would appreciate any guidance that anybody can give to put my mind ar rest

Many thanks

 

[noseall]

If it ain't broke then don't fix it.

 

[dchopp]

Thanks noseall but I feel that it is broke.

I am seeking opinion on putting at least a membrane down which installers seem to recommend. A friend has suggested putting ply initially on the screed in order to raise the floor level but this sounds like doing something just for the sake of it.

What do you think?

 

[alittlerespect]

With this type of flooring detail it was normal practice to lay an over-site concrete of around 4" (100mm) thick, this would not have been an exact science, a bitumen impregnated board would/should have been inserted around the perimeter edge prior to the over-site concrete going down to provide room for expansion of the concrete slab and to avoid breaching the dpc, then when the concrete had cured (around 28 days) 3 coats of damp proofing liquid 'syntheproof' would be applied to the over site concrete which would have been dressed up the wall to meet the dpc, the last coat of syntheproof would receive a sand blinding and on top of this would go a 2" (50mm) sharp sand and cement screed which would have levelled the floor ready to receive the timber finish.

The fact that you do not have any damp problems would suggest that this was the form of construction used.

If you are going to lay a ply deck down, you must ensure that you do not fix through the underlying dpm otherwise you will have problems - as noseall's says - 'if it ain't broke don't fix it'!

So, don't worry about the membrane, and you will sometimes find that the adhesive recommended for fixing the flooring has the inherent property being damp proof, which provides additional benefit - hence the original adhesive being a bitumen based product.

Regards

 

[dchopp]

Thank you 'respect' for this very useful information. If possible can you help me a bit further. At the edge I cannot see a bitumen impregnated board, would this be covered by the screed.
I mentioned that I can see the DPC in the wall as plaster has come away and a damp meter test shows dampness under the DPC although as I said the floor area is dry. Is this damp reading normal as I feel I should investigate this further. Thank you.