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Concrete/Screed flooring project (Read 1901 times)
andyl3004
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Re: Concrete/Screed flooring project
Reply #9 - Mar 24th, 2018, 1:08pm
 
Too late. Screed laid on top of insulation which sat on Dpm. Let's see ...
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Re: Concrete/Screed flooring project
Reply #8 - Mar 22nd, 2018, 12:25pm
 
+1

and if you were planning on putting the DPM under the insulation you need another plastic sheet above to prevent water in the screed floating the insulation.
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woodsmith
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Re: Concrete/Screed flooring project
Reply #7 - Mar 22nd, 2018, 9:45am
 
andyl3004 wrote on Mar 21st, 2018, 6:47pm:
Thanks all. Two follow up questions.  I thought foil backed insulation reacted with some Portland cements so should be avoided?


You would need a damp proof membrane between the concrete and the insulation so there would be no contact, but I've just looked on the Celotex website and they are not recommending using it under a slab so you are right it's better to find a different insulation material, but you may have problems finding a suitable one thin enough.

For .1 cubic metres you will only need a couple of bags of cement but I wouldn't use the plastering sand it's likely to crack. Best to use all sharp sand.



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Re: Concrete/Screed flooring project
Reply #6 - Mar 22nd, 2018, 7:47am
 
Thanks Scruff. Just rechecked the app based calc I did and I inputted the wrong info so thanks for checking that.
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Re: Concrete/Screed flooring project
Reply #5 - Mar 21st, 2018, 10:44pm
 
2m x 0.5m x 11cm works out at approximately 0.37yd³. (0.116 cubic metres)
or 10ft³ without insulation, so you are going to have a lot left over unless you have other work
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« Last Edit: Mar 21st, 2018, 10:51pm by thescruff »  
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Re: Concrete/Screed flooring project
Reply #4 - Mar 21st, 2018, 6:47pm
 
Thanks all. Two follow up questions.  I thought foil backed insulation reacted with some Portland cements so should be avoided?

Second, this space after insulating requires about 1 cubic metre of screed. At a 4:1 mix what number of bags of cement would this require? I have a tonne of old plastering sand which was for tender to which I will add some smaller bags of sharp sand for extra grit, just want to have enough cement before starting.

Thanks again
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Re: Concrete/Screed flooring project
Reply #3 - Mar 20th, 2018, 7:39pm
 
woodsmith wrote on Mar 16th, 2018, 11:15am:

If you are planning to extend the tiles from another room into the porch I would fit a flexible joint between them as you are just asking for a crack to appear if you tile over any joint between two rooms.


I have a crack in a stone floor to prove it.
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Re: Concrete/Screed flooring project
Reply #2 - Mar 16th, 2018, 11:15am
 
The Scruff is right you will need at least 75mm of screed on top of your insulation. You can get foiled sided insulation board in various thicknesses  and I would pick one that gives you space to lay 75mm of screed on top.

Alternatively you could fit 90mm of insulation and lay 22mm flooring grade chipboard on top, which you could then tile on.

If you are planning to extend the tiles from another room into the porch I would fit a flexible joint between them as you are just asking for a crack to appear if you tile over any joint between two rooms.
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Re: Concrete/Screed flooring project
Reply #1 - Mar 15th, 2018, 1:17pm
 
Not a pro for this they will be along later. I would think you'd need at least a 75 mm screed on insulation, maybe less with reinforcing mesh
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Concrete/Screed flooring project
Mar 15th, 2018, 11:50am
 
Hi

I have a new brick porch around the base of an old UPVC one. The concrete base with quarry tiles is still in place. The new bricks went ontop of this and the DPM is two courses up with some polythene folded back down to the old floor. I need to in fill this 2 x 0.5m space with about 110mm to bring it to the right level for new tiling and not to bridge the new DPC.

After laying down a full piece of polythene and taping it to the old pieces, and taping a foam perimeter, can I just fill with polystyrene leaving minimum 50mm to screed on top of? Or am I best to fill with concrete rather than screed? I'd rather not do 50mm of both as will not be able to insulate at all and it will be more work.

Thanks

Andy
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