Waterproof concrete

[Squaredy]

Us Arbtalkers seem to know about most things, so anyone advise me on waterproof concrete?

 

I will be putting a reinforced concrete slab down later this year for a garden room and I do not want to use a plastic membrane - I know from experience that the edges and corners are just a nightmare to do properly.

 

Anyone got experience of actually laying waterproof concrete?  I will be buying in ready-mixed concrete so I will ask local suppliers what they suggest.  But maybe some of you guys have experience of doing this?

[Woodworks]

Our BC officer said the plastic membrane was mainly there to stop the concrete drying  out too quickly which would weaken it it. He reckoned concrete was pretty much waterproof anyway.  Bit of this wont hurt 

Everbuild 202 Integral Liquid Waterproofer 5L

WWW.TOOLSTATION.COM

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Long term water protection to mortar, concrete and rendering. BS 4887. Hazard safety codes: Xi, R36, R38, R52, R53.

 

[eggsarascal]

No personal experience, but I was doing the drains for a basement flat down the smoke the other lads were using something called Sika.

[Conor Wright]

14 minutes ago, eggsarascal said:

No personal experience, but I was doing the drains for a basement flat down the smoke the other lads were using something called Sika.

Sika do a whole range of building materials. Very popular across russia and eastern Europe. They make excellent insulation and insulated blocks under the ytong brand. 

 

[Johnsond]

1 hour ago, Squaredy said:

Us Arbtalkers seem to know about most things, so anyone advise me on waterproof concrete?

 

I will be putting a reinforced concrete slab down later this year for a garden room and I do not want to use a plastic membrane - I know from experience that the edges and corners are just a nightmare to do properly.

 

Anyone got experience of actually laying waterproof concrete?  I will be buying in ready-mixed concrete so I will ask local suppliers what they suggest.  But maybe some of you guys have experience of doing this?

Concrete is in itself waterproof if thick enough, end of day there are concrete rigs and even hulls out there at sea. I’d lay a plastic membrane below the whole pour and build the shutter reinforcement etc etc on it. There are loads of different types of additives out there that can improve its properties but the price starts to go up if you order them from one of the bigger suppliers. Best thing you can do is tell them what you want it for and the tech guys at the supplier will give you a spec, end of the day they are supplying thousands of cubes of the stuff. 
concreting is like many things it’s all about the prep, make sure the shuttering is spot on as nothing worse than watching it pop. Powerscreeds and power floats are east to get from most big hire chains too. 
Are you building walls up from the base or is it a timber type structure ??

how many cube ??

Edited May 16, 2020 by Johnsond

[Squaredy]

1 hour ago, Johnsond said:

Concrete is in itself waterproof if thick enough, end of day there are concrete rigs and even hulls out there at sea. I’d lay a plastic membrane below the whole pour and build the shutter reinforcement etc etc on it. There are loads of different types of additives out there that can improve its properties but the price starts to go up if you order them from one of the bigger suppliers. Best thing you can do is tell them what you want it for and the tech guys at the supplier will give you a spec, end of the day they are supplying thousands of cubes of the stuff. 
concreting is like many things it’s all about the prep, make sure the shuttering is spot on as nothing worse than watching it pop. Powerscreeds and power floats are east to get from most big hire chains too. 
Are you building walls up from the base or is it a timber type structure ??

how many cube ??

Thank you for the input so far.  My research and experience suggest to me that normal concrete is permeable to a degree.  Certainly not dry enough for my purpose without some sort of waterproofing or membrane.

 

It will be a simple reinforced raft foundation with a simple wooden structure sitting on top.  Probably 150mm deep, but maybe getting nearer to 200mm in places.  About 6 cubic metres in total.

 

I agree about the shuttering I will make sure this is good, I do know how much easier it is when this is done right.

[donnk]

additives can be added to make conc into a DPC layer as some builds use this as the DPC where plastic cannot be used.

[Husqvarna King]

Concrete is permeable, seen it before but I concreted some drop down bollards with normal concrete, they are inside undercover and even though in a concrete Wellington they still fill with groundwater in winter and a lot of it. I was surprised how much.

If I remember correctly I think you have to be careful with waterproofer and reinforcing not sure if they go together. Good luck ?

[Dan Maynard]

Thank you for the input so far.  My research and experience suggest to me that normal concrete is permeable to a degree.  Certainly not dry enough for my purpose without some sort of waterproofing or membrane.
 
It will be a simple reinforced raft foundation with a simple wooden structure sitting on top.  Probably 150mm deep, but maybe getting nearer to 200mm in places.  About 6 cubic metres in total.
 
I agree about the shuttering I will make sure this is good, I do know how much easier it is when this is done right.

I hired steel shuttering when laying my garage base, Jewsons if I recall. Spot of weld on the corners just to be sure (didn't ask, they didn't say no, cleaned up afterwards anyway).

[Johnsond]

3 hours ago, Squaredy said:

Thank you for the input so far.  My research and experience suggest to me that normal concrete is permeable to a degree.  Certainly not dry enough for my purpose without some sort of waterproofing or membrane.

 

It will be a simple reinforced raft foundation with a simple wooden structure sitting on top.  Probably 150mm deep, but maybe getting nearer to 200mm in places.  About 6 cubic metres in total.

 

I agree about the shuttering I will make sure this is good, I do know how much easier it is when this is done right.

Buy a roll of visqueen and once you have levelled and sorted the base put this down and everything thereafter goes on top of that, that’s no more than you will ever see done on sites. 150-200mm of decent concrete on top of a membrane you will have no probs. The timber structure no doubt will be on it own timber sole plates which you can also put a dpc in between those  and the concrete.