Damp ? Concrete Floor

[Dabbler]

When people walk into our living room, they exclaim: "ooh ! - paving slabs". After a while, they say "Oh, its only concrete, but hasn't it been laid well". I think the latter is true. House is one of five in a terrace, converted from a mill in 1902. All living room floors are identical, so pretty sure floor is about 100 years old.

Sometimes, small areas of the floor, particularly around the fireplace, change colour, becoming darker than usual. My wife reckons this happens when it rains. I'm not so sure: I think it might coincide with heavy occupation (many people breathing, cooking etc).

My wife says "Oh no, we've got damp coming up through the floor. We'll never be able to sell the house !". She wants to rip up the floor and replace it. I think that's nuts. Apart from colour change, floor doesn't feel damp, no salt deposits - I even tried laying cling-film on floor to see if "damp" would accumulate - but floor is so dry that cling film won't stick and eventually blows away. So I don't think we have a damp problem at all. This is causing much domestic tension.

Also, over the years people have dripped paint on the floor, mixed render on the floor, and generally disrespected it. I wonder if what is changing colour is layers of soot ?, varnish ? grease ? or who knows what has ended up on the floor over the years. I'm inclined to take a serious power cleaner to the floor, e.g. the STR701 Multi Preparation System ( see

) to get rid of paint, drips of render, and anything else that's lurking there - and then seal the floor with that transparent concrete sealant stuff.

Wife says: "Why waste =A3200 pounds on machine hire and consumables when you'll only have to rip up the floor anyway ?".

Is anybody out there brave enough to step into this argument. Anyone had similar floor, or experience with the STR701. We would both value your opinions !!

[The Medway Handyman]

Only to ask if you have used that sort of machine before? If not, there is a distinct knack involving keeping it balanced - otherwise it will throw you all over the room :-)

[Mark S.]

Mine were in terrible condition, I took a layer off that had seperated from the layer below, self leveled the lot then spent ages trying to lay tiles in the kitchen that was still not flat.

If I'd had the money when I originally bought the house I'd have had the lot taken up and redone with proper damp proofing and insulation etc. You live and learn as they say. ;-)

Mark S.

[Dabbler]

Thanks, Handyman - no, never used this machine before - can you describe the knack ?

[The Medway Handyman]

With difficulty :-)

What you have basically is a motor, running clockwise, on the end of a stick (handle). The handle is adjustable to reach a comfortable height, but once locked its rigid.

The brush/pad/disc rests on the floor. If it's perfectly flat on the floor it will stay where it is spinning merrily away eventually grinding a hole in the floor.

Machines like this are generally used in a side to side motion.

To move the machine right or left you apply slight (and I do mean slight) upwards or downwards pressure to the handle. Raise Right Lower Left.

What happens is, if you raise the handle silghtly, the weight of the machine is on the front edge of the disc, Since its revolving clockwise it will move to the right. Lower the handle & it goes the other way.

Twisting the handle puts the weight on the left or right of the disc & it will move backwards or forwards.

It will take a little practice, (prefereably in a wide open space) to master. Bit like Judo, use the machines power to control it.

Don't be tempted to try & out muscle it! That thing has a 2hp motor coupled to a 10-1 reduction gearbox - the torque is incredible.

[Dabbler]

upwards or downwards pressure to the handle. Twisting the handle puts the weight on the left or right of the disc & it will move backwards or forwards.

Aha, gotcha! A very clear description! Sounds like the kind of thing you have to relearn every time you do it. Many Thanks.

[meow2222]

If the floor lacks a dpm, a sealer will prevent surface evaporation, and it may become damp then wet. If this occurs you then get a damp problem with the base of the walls. A safer option would be to carpet over it using carpet with a permeable backing. Once carpeted there is no sale issue.

NT

[The Natural Philosopher]

I know its Monday, but REALLY...;-)

[MB]

This is just a thought-- probably has nothing to do with anything: I've noticed in our bathroom that the grout between the floor's ceramic tiles, particularly near the outside wall, darken when there's lots of moisture in the room, like when I've hung up something damp, like two bedsheets. I've assumed that it's condensation on the cool floor.

[The Natural Philosopher]

If it varies with internal humidity, probably yes.

You get a nice thermal gradient across a concrete floor towards the house exterior.

More heating and ventilation needed?