damp in concrete floor

[Anonymous]

Just moved into a circa 1900 sandstone cottage. Removed 'out of keeping beech' laminate flooring to reveal damp on the concrete floor. Called in specialist who got readings of 25% on damp metre. His advice was to monitor the situation over the winter as the house had not been continually lived in for approx 6 months. Carpet and underlay already brought and paid for, should we lay it?

 

[Anonymous]

Not unless you want to ruin it.

Personally I detest concrete floors. They alwasy seem to get damp and cause problems.
I have got a concrete floor in my current house (covered by oak effect laminate), which I am going to dispose of if we dont move this year.

Is there somewhere that you could take up some of the concrete to see how deep it is ? It's often put in as a 'solution' to damp with a plastic membrane underneath. Is it damp all over or in specific areas like doorways or round the edges of the room ?

Can you lift floorboards in an adjacent room to see how deep it is ? In my case its just a couple of inches on soil so I have taken up the concrete in the scullery and laid a brick floor on lime mortar to see how that handles the damp, if all ok then I will replace all the concrete with flags.

 

[Anonymous]

It is not everybody who wants or can afford to install a whole new floor. So, as a builder, I have had to get over this one before. I am not saying that my solution is appropriate to old buildings or that it is a demon fix. However ---- cost is cost.
I can't remember the name of the product but if you describe it to a specialist floor company they will probably know what you mean. You buy a two pack product that, when mixed together sets off to an impervious membrane. This you paint on the floor and then put a latex self levelling compound on the top. Make sure that your carpet fitter sticks down any gripper track etc. and does not nail it through your brand new dpm!!! I think it is called ES3000 but I may be wrong as I don't use it often. To the best of my knowledge this quick fix has always worked. Good luck and I hope I am not ostricised for recommending something like this!!!! Mike.

 

[Anonymous]

Problem then being that the damp in the floor will be driven up the walls.......

 

[Anonymous]

Hello Vanessa,

I would give the floor some time to dry out before panicking. I have concrete floors throughout my Victorian basement flat, and when I moved in the existing carpet was damp. However, the concrete dried out really quickly after taking the damp floor-covering up.

One thing I've noticed living with concrete floors is that if you spill anything, it will not dry out of its own accord, you need to help it along. Now that I'm propery ventilating and warming my flat, the replacement carpets show no sign of damp.

Also, re. your meter reading. I had a valuation survey for remortgage done recently, and the meter did the whole red-light thing when held to my vinyl-tiled concrete hallway. The surveyor was completely unconcerned by this, saying it was exactly what you would expect in a concrete-floored basement flat, and reminded me that meters are designed for taking readings on wood, not concrete or plaster. A good meter reading can definitively say "this floor is not damp", but the same cannot be said of a 'bad' meter reading - it is not conclusive.

Hopefully your damp patch will dry out in time and you can learn to live with your concrete floor as I have done - not having the finances or DIY skills to do much else!

 

[Anonymous]

I don't think 25% moisture content is possible in concrete - wet concrete only contains about 8%, and the scales on dedicated moisture meters usually only go up to 6 or 7%.

Anyhow, If I were you I would leave it a while and monitor the moisture content yourself. It's dead easy - take a sheet of polythene about half a meter square and tape it to the floor. Leave for 24 hours. You will soon see if there is any moisture in the floor.

 

[Anonymous]

I am not entirely convinced by the argument that putting a dpm in a floor will drive moisture up the walls. Maybe I have just got lucky but I reckon that the damp problem would have to be pretty severe for this to happen.
Like I said it is a comparativly cheap way of overcoming a problem for those that cannot afford the ideal. Mike. solution/s.

 

[Anonymous]

I do think that putting a DPM into a concrete floor can cause problems in some period buildings. In reality, this is designed for modern buildings where it is combimed with a dpm to form a continuous seal.

The moisture has to come out somewhere, and that somewhere can be the walls. If the walls are able to allow the moisture to then easily escape, ie via lime mortar, well ventilated, that may work, but it also may not.

My own experience with flagstones laid on earth covered with plastic flooring convinced me of the truth that moisture can be driven up walls if it has no other means of escape.

Stephen did a long post about this a while ago, which it may be possible to find via a site search.