What to use to seal an interior concrete floor ?

tadpoleuk

I have a room in my house that has a concrete floor. A neighbour said the room was flooded about 15 years ago, before I moved in and the council have removed the floorboards and replaced them with concrete.

The room has always smealt a bit mouldy so now I have removed the old carpet I would like to seal the floor before I lay a new one.

I pulled up the old carpet because it felt moist when I walked on it in barefeet and when I got down and smealt it , it had a mushroom odour. I was expecting the floor underneath to be black or damp but it looks fine, apart from the gripper rods have gone a bit black in places.

Things that have been stored in the room like the furniture have been getting a layer of grey mould on, and the clothes in the drawers smell stale and musty. .I was told concrete leeches up moisture from underneath ?

Sooo I have been looking for something to use on the floor

I have been told to use garage floor paint, PVA glue, concrete floor sealent or damp shield. Any advice on what would be best, I want to stop the floor smelling and any moisture that has been coming up through it.

Any advice please ?

Thank you

Doozergirl

You'd have to dig it up, insulate it and lay a proper damp proof membrane down to have any proper effect on it. It sounds like a proper issue.

MX5huggy

If there is no damp proof membrane (plastic sheet) under the concrete, any surface treatment is not really going to be effective. Is it damp all over or at the edges?

tadpoleuk

The actual concrete floor feels sort of dry to the touch, but very cold, especially near the exterior wall. The carpet that was on it felt damp and cold. There is no mould on the floor surface , just the gripper rod has gone black in 2 corners,. though the carpet was black on the edges all round the room. The nails holding the gripper down look rusty along that exterior wall . My hands stink now I have been touching it I have sniffed the floor and the smell is coming from all over.

Now the carpet is up the room smells even stronger of mushrooms and concrete. OMG rip the concrete up ? I was hoping to seal the floor lay the carpet and have the room finished in a couple of weeks.

Wouldn't the council have put down a membrane before they put the concrete down ?

I have had a looked at the exterior wall and there is a series of 2 holes in each brick running along the bottom row. Is that a damp course ? There is no little flap of material hanging out the wall, like I have seen on my mums house. How would I know if there is a membrane underneath without ripping up the floor ?

wallbash

How would I know if there is a membrane underneath without ripping up the floor ?

Cant help you , BUT can suggest a way of 'testing'

Dry a bit of concrete, Put a ring of plasticine on the floor.
Up - end a glass ( or jar ) Make a good seal with the plasticine.

If the moisture is coming up thru the concrete , the water will condense on the glass.

Wouldn't the council have put down a membrane before they put the concrete down ?

Yes, a fairly basic idea.

tadpoleuk

OOoo thats a good idea. Thank you I will try it, dont have plasticine but Im sure I can find something suitable. I will do it now.

MX5huggy

Is all the skirting on? could you take a bit off so you can see the edge where the concrete meets the wall, should be able to see any membrane here, might need to knock a bit of plaster off.

myrnahaz

Are you sure it's not condensation? That would make the carpet and grippers black in the corners and on the edges. Is the room well ventilated? Wooden floors have plenty of air movement due to vents in the walls under the floorboards, so concreting the floor might have removed the only ventilation points in the room. The black mould would also smell mushroomy - maybe you just need to remove the gripper rods and wash the floor in a bleach solution ( or squirt dettol mould and mildew spray over the offending areas - smelly but it works in minutes).

PS - open a window while you spray, and permanently improve the ventilation to stop it happening again.

wallbash

Are you sure it's not condensation?

Thats my guess
But the OP wanted to 'seal' the floor. I can't imagine anyone not putting a DPC under the concrete,. So its one step at a time.

I was hoping to seal the floor lay the carpet and have the room finished in a couple of weeks.

I don't think you will :rotfl:

tadpoleuk

I have had my glass sealed on the floor all night but no water has formed in it yet.. .

Yes it could be described as having poor ventilation compared to the rest of the house, Only one airbrick in the chimney breast.
I think I can feel a draught coming through where the skirting meets the floor.

Im going to bleach it today, I have only just papered and painted in there so I am loathed to rip off a skirting board. My neighbour has been to have a look and he thinks its had a chemical damp course injected to one of the outside walls.

The concrete is crumbling a bit where it meets the floorboards in the hall doorway so I am having a dig down, I didnt expect the concrete to be so thick. No sign of a membrane yet.

I suppose its time to call someone in to have a look. Thanks for the suggestions