# waterproofing concrete blocks



## gwr (7 May 2013)

I am still looking to build a workshop out the back, originally it was to be down 1 side of the garden at about 3m x 6.5m. 
After some negotiations with Er Indoors it can go along my back boundary which has a 6ft fence backing onto a sports field and a 6ft fence either side.the total lenth is 9m and i can come 4m forward from the fence. So to use all the space i can there would be no room to get at the back to roughcast the blocks is there any way i can waterproof them with only a 6-12 inch space between the fence and the blocks?


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## monkeybiter (7 May 2013)

I like a good 12" - 18" roof overhang if possible, it protects from most rain.

Now I'll make way for the planning/building reg's posts. :wink:


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## gwr (7 May 2013)

Thanks Monkeybiter i was thinking of a flat roof so only about 2-3 foot will be exposed above the fence my thought was to roughcast the blocks that can be reached from over the fence with a bellcast about fence hight and i could overhang roof to the boundary fence but would be gutted if i had damp problems after going to the expence of building it. Iwas wondering if there was anything i could spray the blocks with to stop water penetration. Im aware of the 30sq m building control hoping to get 36 sqm and 3 mtr hight for flat roof.


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## Phil Pascoe (7 May 2013)

There are very good products that can be painted on, but it's a while since I've seen them used so I don't remember the brand names.You could do a couple of courses at a time as the blocks are laid.


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## gwr (7 May 2013)

Thanks Phil im searching paint on products at the minute but reviews are mainly saying great on smooth concrete but hitty missy on the blocks. I will keep looking thanks and as im planing on giving the build a go myself painting every couple of rows will be no problem thanks.


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## nev (7 May 2013)

aquablock BB any good?
http://www.aquasealeurope.co.uk/ABlock-Installation.pdf


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## sawdust1 (7 May 2013)

Hi gwr, Thompsons water seal i have used it on brick work. Get the spirit one not the waterbased one brush on several coats. Or render the finished wall with SBR added to the mix used it on walls below ground to keep out damp. Hope this helps


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## gwr (7 May 2013)

Thanks Nev i will have a look into that Aquablock bb. Sawdust would that SBR mix be ok to use rendering 3 blocks high at a time creating joins in it? or i could feather it with an overlap just thinking out loud! thanks for your help lads.


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## Cowboy _Builder (7 May 2013)

You should revise your plans as you are only allowed a "Maximum height of 2.5 metres in the case of a building, enclosure or container within two metres of a boundary of the curtilage of the dwelling house." ...You don't need to inform the LA but it's advisable to do so because if someone objects to your building and it doesn't comply you will have to remove it .
My workshop in Spain is built from concrete blocks ,I rendered the inside with waterproof tile adhesive ,it has soil 3ft high against the out side wall and has never let any damp through .

Have a look here .... 
http://www.planningportal.gov.uk/permission/commonprojects/outbuildings/


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## gwr (8 May 2013)

I have miss read that part about the 2 mtrs from boundary so 2450 at the highest point it is then.I suppose it will save a few quid in blocks  . cheers CB


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## Phil Pascoe (8 May 2013)

You can go higher, but you need planning permission.


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## Lons (8 May 2013)

Do a google for "tanking" methods. Many of the bitumen based products are suitable but would need to be applied as you build as the mortar joints need to be protected as well. It would slow up the work as the mortar would need to dry out before application.

Not a problem if you could reach after it's built with a roller on a long pole for example.

Bob


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## alf48 (21 Jul 2013)

P V A diluted 5 to 1 in a fence sprayer,but you should get some protection from the weather from the neighbouring fences,althougth being so close ,having no ventilation could cause algae ,hope this helps ......regards alf


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