Engineered wood flooring over damp concrete

[gigakid]

Hi, hope someone can help me here.

We recently removed laminate flooring in a new property, uncovering wooden floorboards downstairs, and found that where a chimney hearth had once been there was a flush concrete slab. About a quarter of the slab is prone to damp and you can feel moisture coming up through it especially when weather has been bad.

We now wish to lay a new solid wood floor, but I am convcerned about putting this down, whilst there is a potential damp problem - a floor fitter recently checked moisture and said it was quite high and that he could fit the floor but not give a guarantee whilst there was this small area of damp.

I wondered if an engineered floor would be more suited to this, as I read the have better temperature and humidity stability and can be used in cellers wherreas solid wood cannot?

Also would a damp proof membrane help being spread over the area which is prone to moisture?

One of the flooring guys I had round said that f the damp hadn't affected the laminate florring (it hadn't) then it wont affect wood flooring?

With regards to the damp itself I am getting conflicting info ranging from one extreme - "this is natural in houses like this and is nothing to worry about" to the other "its very serious, and if you dont address the damp issue it will penetrate the whole of your ground floor as et then dry rot"

I will also post this in the buildings section to try get specific advice on the damp issue

 

[WoodYouLike]

I wondered if an engineered floor would be more suited to this, as I read

Not when you have a damp problem! Solve that first, then decide on the floor type.

 

[gigakid]

Note to moderator:

You have deleted my post in the buildings forum, however this was not a duplicate and I would argue it has been incorrectly deleted!

My other post was asking questions specific to a damp problem which forms part of the overall diy issue.

Had I askerd the same questions in this forum it would have been bumped for being in the wrong category!

The post you deleted was receiving posts specific to the damp issue it related to so I think it has been deleted with a heavy handed approach not taking full account of the content of the post.

 

[mattysupra]

you can treat with surface dpm but very expensive and not reall worth it. I would suggest you dig out the concrete hearth and install joists and complete with floorboards.

 

[Symptoms]

Kid - new house or old house? Is the chimney breast still in place? Ground floor or upper floor hearth?

Assume old house. These hearth slabs are either supported on a sleeper (or dwarf) wall, back-filled with spoil/rubble, with the hearth slab cast on top and unlikely to have any dpc; or, suspended at the 'room' end on a fillet fixed to a joist (assumes the joists run parallel to the fireplace wall). Clearly, your problem I reckon is coming up via the spoil/rubble/sleeper.

The correct remedial action is, as matty suggests, remove the slab, etc. etc. Your problem then is the joists - you will have to bridge the new gap with treated timber bolted to the existing joists (make sure you cut away any rotten timber well into good stuff).

If your slab is suspended then the damp must be coming in where it meets the wall/chimney breast; again whip the hearth out and check for obvious causes for the damp getting in. Maybe the dpc in the wall has been bridged outside (very, very common). Lets us know so we can suggest a solution.

Don't forget to check your airbricks for good under-floor ventilation.