Do I have a damp problem?

[J_N30]

Hello,

I own a 1985 3 bed semi with concrete downstairs floor. I decided to lay new flooring downstairs and after removing the carpet, underlay and tiles the buliders stuck down i decided to test the floor with my £10 damp meter and it is showing that damp is present (audio type meter) Originaly i thought that this was because the door wasnt sealed underneath as i tested in the hall way near front door.
Tonight i tested under the carpet and tiles in the dining room where no doors are present and the meter is beeping again. The concrete isnt wet or damp to touch, just cold.

Do I have anything to worry about or is just because im using a typical cheep DIY testing meter.

Ive tested all the walls and they seam fine.

Thanks for your help.

 

[^woody^]

Put the meter on your finger and see if it goes off

Now, do you have a damp problem?

 

[alittlerespect]

Hi

More than likely to be a spot of thermal bridging which is causing some interstitial condensation.

Choose an area and monitor it on a regular basis throughout this winter and summer and if it is interstitial condensation you should find the moisture content reducing in the summer months.

Unless you are willing to introduce some floor insulation its a problem you will have to live with.

Regards

 

[J_N30]

Thanks for the replys, Will I be ok tiling over the concrete as previously planned?

 

[alittlerespect]

Hi

The thermo-plastic/vinyl tiles that were put down by the builder would have been acting as a vapour barrier and rather than the moisture evaporate is has caused the local area of the concrete floor beneath the tiles to sweat.

There is no problem with tiling over the concrete however as a word of caution I would mention that tiling the floor area will create a colder floor due to the differing thermal conductivity of the materials being used.
To overcome this problem there are 2 solutions: 1. Put down some insulation before you lay the tiles; or 2 get a bit more serious and combine a heating element with the insulation board.

There is a third option and that is to go with the risk and do nothing, however, doing nothing will leave you with a cold floor in winter months, and given the likely area of the floor the heat loss can be quite significant.

Before making any decision - If you do a web search on underfloor heating you should find ample information on the kinds of solutions that are available.

Regards

 

[JohnD]

if you want to see if the concrete has damp, tape a piece of clear plastic tightly to it. If water forms on top, it is condensation from the room. If water form underneath, it is coming up through the floor.

By 1985, your concrete slab should be on a polythene DPM. Sometimes they get damaged, and sometimes pipes laid in the concrete leak.

 

[J_N30]

Hi

The thermo-plastic/vinyl tiles that were put down by the builder would have been acting as a vapour barrier and rather than the moisture evaporate is has caused the local area of the concrete floor beneath the tiles to sweat.

There is no problem with tiling over the concrete however as a word of caution I would mention that tiling the floor area will create a colder floor due to the differing thermal conductivity of the materials being used.
To overcome this problem there are 2 solutions: 1. Put down some insulation before you lay the tiles; or 2 get a bit more serious and combine a heating element with the insulation board.

There is a third option and that is to go with the risk and do nothing, however, doing nothing will leave you with a cold floor in winter months, and given the likely area of the floor the heat loss can be quite significant.

Before making any decision - If you do a web search on underfloor heating you should find ample information on the kinds of solutions that are available.

Regards

Thanks for the reply, The area im tiling (hallway) is approx 1.5m2 and has a radiator. if i were to go with option 3 am i going to cause damp problems under the tiles?