25mm concrete depth on top of damp membrane

[McTrucky]

In my brick built garage I have two issues.
1 - Dampness comes though the concrete floor and there is usually condensation in the garage during the winter.
2 - When we have intense rain fall, water can not drain fast enough from infront of the garage so seeps under the door flooding the front part of the garage. This happens at least once a month on average (got to love Scottish weather).

I am thinking about laying a polypropylene sheet with about an inch of concrete on top to attempt to address both issues. I am worried about how thin the concrete would be, and if it will crack and break up. I could use fibres in the mix to strengthen.

The existing floor is not polished smooth, so I am not able to ensure there will not be small air pockets trapped under the poly sheet.

Any thoughts or advise?

[jfdi]

I can't see 25mm of concrete being anywhere near thick enough to resist cracking even with just foot traffic never mind a car on it. Liquid screeds normally require around 50mm in a house.

[Lotobear]

An unbonded traditional screed of less than 65mm is likely to curl so 25mm is a complete non starter I'm afraid.

I would look at an epoxy surface DPM

[rdjohn]

Perhaps a 25mm granolithic screed on top of an epoxy bonding agent could achieve what you are after. Its not a DIY solution unless you are very skilled with a trowel and mixing.

A typical 1:2:4 mix with 19mm aggregate is very unlikely to achieve a good result. It is just way too thin.

[McTrucky]

Thanks all. I will re check and see if I can go up to 50mm. Not sure how high the damp proof is set on the brickwork. Probably doesn't matter.

I did think about one of the paint on membranes, but that wouldn't address the flooding issue.

[Rob.]

Could you not address the drainage outside the garage door?

[Fatboy]

Also perhaps a french drain dug round the garage, get the water away from it before it seeps through the concrete, couple that with an epoxy resin screed and it would probably sort it out?

[McTrucky]

External drainage is a major thing. Not going to be fixed anytime soon - but yes, this would be ideal.

[Rough101]

Heat recovery vent unit would be my first choice to just keep it drying out.

[paulwirral]

McTrucky said:

External drainage is a major thing. Not going to be fixed anytime soon - but yes, this would be ideal.

Post a pic of the outside of the garage so we can advise better , otherwise it’s just a guess .