Sealing a garage base to reduce compensation

[ARW]

I suspect not. He needs insulation on/below the roof and ventilation into the garage.

[ARW]

Sometimes the simple answers are the best ones.

And that is the best answer.

[Bert Coules]

Thanks for the additional thoughts. I occurs to me that maybe something as simple as leaving the garage's one small window open might make some sort of difference while other solutions are being considered.

There must be *something* about this particular garage that's making the problem worse than usual: I remember getting some condensation before I converted mine, but nothing like on this scale.

Bert

[Bert Coules]

I'll try it. I don't think I'll be able to seal off the floor completely - there'll surely be access for water vapour round the edges - but I can certainly reduce the massive area open to the air. Thanks to Polygonum for the suggestion.

Bert

[The Medway Handyman]

The roof is obviously the coldest area, so the water vapour condenses there. You need to look at that and the source of the moisture. I think the floor is a good start - if the concrete has no DPC under it.

[ARW]

Ever considered taking up writing for a living ;-)?

[The Medway Handyman]

It would, but if the floor is that damp it may not last long. Maybe there are specific coatings for this problem?

[Bert Coules]

I'm pretty certain that it hasn't. If that does prove to be a major factor perhaps one solution would be to put down a DPC and screed over it, but presumably a certain thickness of screed would be necessary for solidity, and the headrom in the garage is minimal already.

Bert

[Bert Coules]

"headrom". I'm going back to bed.

Bert

[The Medway Handyman]

You can use a paint on DPC & a 2" screed.

[Phil L]

None of these are of any use to you - they are for sealing paving against algae growth and staining, they are not sealants against penetrating damp, you need something that creates a barrier. I've just used Thompsons roof seal on my concrete shed roof, it's water based and applied with a roller. It pissed it down 4 hours after I'd done it and half of it washed off onto the pavement, but in the time it was on it sealed the (bad) leaks I was having and I've enough left to give it a second coat when it dries.....it has a 10 year warranty and I've used it before on shed rooves with no probs...it's about £30 for 5L

[Bert Coules]

Thanks for that. Would the same product work against rising penetrating damp if it was applied to the surface of a concrete base?

Bert

[Bert Coules]

Two inches would be workable as far as headroom is concerned. Thanks.

Bert

[harry]

It should help. My garage floor is painted & I get no condensation at all.

[harry]

The condensation happens when the outside air temperature falls rapidly and warmer moist inside air condenses out on the underside of the cold roof.

So you either get rid of the interior moisture (Seal the floor)assuming it's coming from there (quite common)

Or prevent the interior air from contacting the cold surface. (Insulation).

The first is best because if it doesn't condense out on the roof, it may condense out somewhere else as temperature continues to fall.

How well ventilated is the garage? Ventilation helps.

[harry]

+1

[Bert Coules]

It's ventilated only in the sense that it's not sealed tight. The main double doors and small side door are not particularly close-fitting, and the openings left above the wall panels by the corrugations in the roof sheets are covered only by lengths of 6"x6" metal angle which surely can't be airtight, but that's about it. There's a window, but from memory I don't think it opens.

It's hard to see how that degree of venting could be improved, short of knocking holes in the walls and fitting grills or similar. Maybe one of those non-powered ventilation fans in the window glass?

That's very encouraging. Thanks.

Bert

[Bert Coules]

Sorry, should have asked: what is it painted with?

Bert

[ARW]

Solar panels.

[harry]

Sorry I dunno. It was just a big can of floor paint. I don't suppose it matters so long as it remains stuck down. ie doesn't flake off or anything.

I remember there was instructions to the the effect that the surface had to be dry at the time of a painting but it would keep damp out thereafter. It was quite expensive but it still looks good after six years.

It's quite dry in there, I dry my firewood in there no problems. No condensation on the roof.