Waterproofing 40 year old slab

I have a house that's nearly 40 years old and it has an in ground slab on the ground floor that's below ground level on the side that I'm having a few problems with.

In the process of a drawn out second bathroom renovation and I've noticed that the slab get's a little damp in areas after a lot of rain and we have efflorescence in between a few in the existing tiles in the adjacent rumpus room etc which I'm planning to re tile anyway.

I'm not sure if it's water in the soil (a fair bit of work to reduce any water getting to the house has been done since we purchased) and/or the stormwater pipe that appears to run under the slab (clay pipes) has cracked. I'm going to drop a camera down that pipe to see what is going on in there but in the meantime I need to do something with the slab before I start using the floor levelling compound and waterproofing.

I've looked at a few products but all seem to sit on the surface which isn't appealing as it still leaves the timber for the walls sitting on the slab except for one product called Seal-A-Crete.

Based on the area to be covered I need around 15litres which is around $400 delivered. Product seems to do exactly what I'm after but it would be interesting to see if anyone has used this or heard about it before I spend that money and re tile to find out it's no good!

Any other suggestions would be welcome as well. Around 43metres to treat.

Seal-A-Crete

Benefits:

Stops Hydrostatic pressure
Minimises surface dusting, pitting and hairline cracks
Purges out years of contaminants in old slabs
Compatible with all coatings and adhesives
Trafficable during and after application
100% internally seals the slab for life
Non toxic, Environmentally friendly
Is permanent, cannot be worn off
Penetrates up to 200mm plus
Hardens concrete by 20%
Cost effective

Website: http://www.sealacrete.com.au/index.html

Brochure: http://www.sealacrete.com.au/product...e_brochure.pdf


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