Waterproof concrete

[dumper]

Just now, Squaredy said:

I am going to build a garden room, which will have a snooker table in (possibly full size) and darts board and in the future who knows what else.

I believe you have forgotten to mention the whole wall telly and bar!

[Squaredy]

Just now, dumper said:

I believe you have forgotten to mention the whole wall telly and bar!

Well yes indeed, but the snooker table will not leave much space for anything else....!

[astra25]

It's been said befor but all concrete is water proof here is a pic where there is wet crap under the concrete but concrete remains dry.

 

Iv worked on a new build house with a basement which the walls were 300mm thick waterproof concrete I don't know how much extra it was for the waterproof addictive that was used but I know it were expensive.

 

Edited May 22, 2020 by astra25

[Ratman]

This is my garage/workshop slab, i insulated it but if you dont do yours then fair enough, but the corners etc are all cut neat and stuck back with waterproof butyl tape. I then just tamped off and floated by hand, everything finished up ticketyboo![emoji108]
I highly recommend you use a visqueen as a minimum, and also insulation if you can, makes a huge difference in my opinion.

[Squaredy]

1 hour ago, astra25 said:

It's been said befor but all concrete is water proof here is a pic where there is wet crap under the concrete but concrete remains dry.

 

Iv worked on a new build house with a basement which the walls were 300mm thick waterproof concrete I don't know how much extra it was for the waterproof addictive that was used but I know it were expensive.

 

Water cannot flow through concrete I agree, but apparently it will seep through due to capillary action.  I would love to believe otherwise but I fear I cannot.  

[Squaredy]

1 hour ago, Ratman said:

This is my garage/workshop slab, i insulated it but if you dont do yours then fair enough, but the corners etc are all cut neat and stuck back with waterproof butyl tape. I then just tamped off and floated by hand, everything finished up ticketyboo!
I highly recommend you use a visqueen as a minimum, and also insulation if you can, makes a huge difference in my opinion.

A very organised looking construction it has to be said.  Like all these jobs good preparation makes such a difference.  Thank you for sharing, and where can I buy that stuff you mention....ticketyboo....sounds like just what I need.

[Johnsond]

11 minutes ago, Squaredy said:

Water cannot flow through concrete I agree, but apparently it will seep through due to capillary action.  I would love to believe otherwise but I fear I cannot.  

Visqueen will do the trick the corners are easy to sort , if it’s not tidy at end of job put a timber border around it . It’s easy to overthink all this. Keep it simple ?

[Ratman]

Heres a link for ya [emoji106] i cut mine with a sharp stanley knife on a dust free clean surface, its fiddly tacky stuff but does its job no bother once you get the hang of it.

 

 

DOUBLE SIDED WATERPROOF MEMBRANE JOINTING BUTYL TAPE DPM 50MM WIDE 1.5MM THICK

WWW.EBAY.CO.UK

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Lapping & Jointing construction seals. For best results - Clean all surfaces and make sure they are clean, dry, free of grease, dust, mortar and any other debris.Warming of product may be required if jointing under 10°C.

[Siberianwoodsman]

The secret to waterproof concrete is to use a smaller amount of water in the mix but the problem in that is it does not flow well when poured, so a plasticiser is used, company's that specialise in it will send one of there staff to monitor the mixing to ensure the correct ratio. It's all to do with how the crystals form in the cement as it cures the smaller the crystals the more waterproof the cement is. More water produces more heat and therefore bigger crystals.

[ucoulddoit]

Just seen this thread and looking at the dates, might now be too late to comment? Anyway, after a quick scan through, I didn't see any mention that visqeen serves two purposes. In addition to reducing dampness, it provides a slip membrane. Once the initial setting involving heat of hydration (the chemical reactions) has finished, the concrete will gradually cool and hence shrink. If cast directly onto the ground or hardcore, the friction can sometimes resist the shrinking, creating a crack in the middle if the tension in the concrete exceeds it's strength. That's what the mesh or fibres are usually there for, to resist the early thermal cracking tension forces. The slab should be able to easily slide over what it's sitting on. Waterproof concrete will keep the water out, but cracks through the slab won't! Not relevant here, but a basement structure in a high water table would have water pouring through cracks if not properly detailed and designed. Having said all that, long lengths of slab are obviously more prone to early thermal shrinkage cracking and joints if needed (can be saw cut a day or so after casting) are usually 5 to 6m spacing. I guess the garden room is about this size in which case no joints needed if adequately reinforced and with a slip membrane.

 

Andrew