Help, basement carpet going mouldy under boxes

When bought my house it had no carpet in the basement garage(150sqm) so i bought some second hand carpet and underlay and put it down in the rumpus room at the back of garage. Iv just found 5 big spots of mould under some boxes and suitcases. The carpet has rotted so will need to be removed.

Does anyone know what i can do to stop the damp mould , i think its only coming through in the winter.

Yes, it is a very common thing. You can either pay someone like we did (they did a shit job and it cost thousands so would be better to diy it) or you go to bunnings. Buy a large tin of this white sloppy stuff, it's like swimming pool liner. It's called waterproof sealer and has fiberglass stuff in it. You slap it on in a criss cross fashion and then leave it to dry and harden (takes a couple of days). You have to make sure you cover the area leaving absolutely no holes where the water can get through. When you put carpet on the top, make sure you glue the smooth edge on rather than nail it or you will compromise the seal.

I think you can get waterproof sealant from off here too. I watched the guys slap it down at my place. It is just like thick paint. The crap job they did was allow it to splash up the walls and on the taps, and they didn't rinse it off. It baked on. And then they put floor leveler on, let it dry, and added lino. The silicon edging they used, well they used their hands to spread it out and it is now black and mouldy. They wouldn't fix it, I'm stuck with it.

But the waterproof sealer looked easy. I'd probably slap it a bit up the walls so it gave really good fish tank kind of seal, I case damp rose up the walls. But the bunnings experts may say that's not a good thing to do. I'm no expert by any stretch of the imagination.

We had water getting into a basement bedroom and it was seeping through the concrete block wall as it was half under the ground. In the end we had to dig a trench seal the wall from the outside and put in drainage at the foot of the house. Best to first see where the water is getting in to see how to fix it.

There is one area of the wall that has effloresence coming through, this is only an issue if its covered up. The patches on the floor only where there is no air flow under a box or container. Under the chest of drawers and freezer were fine.

Its a full basement in that everything is underground except the garage doors

Try running a dehumidifier for a couple of days and monitor how much water is collected.

The basement slab and walls would probably not have had the same moisture control installed during construction compared to habitable spaces.

It doesn't matter how long you run a dehumidifier for, you'll never cure the moisture problem.

You could try "tanking" (sealing) it from the inside like others have said. There are professional companies that specialise in that type of work.

It's a very good idea to dig a trench around the outside of the garage to well below the floor level and put perforated Novaflo in the bottom and fill up with scoria. Also paint the floor with goo as above. I used a sealer from Cemix.

There is a drain that runs around the base of the basement that drains into the drain out front of house. I don??

There is a product put out by Ardex,it is a 2 part mix & sorts out this problem,I used it on a garage floor last yr which had HUGE water issues,rising moisture coming through the concrete floor,anyhow,it fixed the problem.For memory it was abt $400 for the product,it is something most handy type folk can manage as long as you read the instructions,also I pressure cleaned & etched the surface so I could get a good adhesion.After it had dried (took a day) it rained &I there was no longer a pool of water on the floor,I tiled it & has remained dry.