Raising a garage floor

[sotal]

I've asked this before but never managed to get very far, so I'll try keeping it basic so I don't confuse things.

I need to raise the level of the floor for my downstairs toilet.

I want to raise it by 2 bricks - approx 160mm.

It's currently a good solid concrete floor.

What is the correct way to raise this by 160mm using insulation and screed? Please can you list exactly what you would do with dpm, and thicknesses of insulation vs thickness of screed - plus any reinforcement.

The toilet is 1.5 x 2m

Thanks

 

[steveb1964]

This may help

//www.diynot.com/forums/viewtopic.php?p=856635#856635

 

[sotal]

Thanks Steve the last post in there does help but it seems a little vague to my simple mind!

d.p.m.

60mm kingspan floor insulation.

95mm screed.

job done in a matter of hours.

That's a similar depth but should there be some dpm between the kingspan and the screed?

Should the Screed have any reinforcement?

Should I have any edge insulation to stop cold bridging?

Does the dpm need to tie in to any existing dpc if there is one?

Could I have more insulation and less screed? Would 100mm insulation be OK with 60mm screed?


Thanks again

 

[smartmart]

Hi there, your screed should be at least 70mm thick, so use 90mm insulation, remembering to allow for any floor finishes (tiles etc.) But why not use 130mm insulation and moisture resisting flooring, its a lot quicker,drier, cheaper.........

 

[sotal]

Thanks for the reply,

I've taken the thickness of the flooring itself into count, and the 160mm is what is required underneath.

90mm seems a bit of an odd size to find, so I may have to drop down to 75mm,

Could you elaborate on how the dpm should go?

Many thanks

 

[smartmart]

Hi again, if your floor is dry now i can't realy see the point of using a D.P.M. your insulation should do the same job as membrane, you could put one there for peice of mind but they do tend to make the corners untidy.

 

[sotal]

Thanks for that - yes it is very dry at the moment but is also quite well ventilated - wheras I hope to seal it up a bit and make it warmer - not sure if that will affect it?

But won't I need a dpm between the insulation and the screed?

Many thanks

 

[^woody^]

Hi again, if your floor is dry now i can't realy see the point of using a D.P.M. your insulation should do the same job as membrane, you could put one there for peice of mind but they do tend to make the corners untidy.

The floor may look dry because any slight damp evaporates away. Insulation is not a barrier,a nd as soon as anything is laid across the concrete, then moisture has the chance to build up and move up

A DPM would be laid on the concrete and then the insulation and screed laid

 

[sotal]

Right OK,

So DPM down first that's fine,


but do I need something between the insulation and the screed?

 

[misterhelpful]

Dunno if this will help:
http://www.sheffins.co.uk/pa_guide/groundfloor_solutions.pdf

 

[sotal]

Thanks for that,

It's hard to see on the picture, but I'm looking at the one for Solid COncrete Floor above the floor slab.



It shows:

Hard Core
DPM
Concrete Slab
Insulation
Vapour Control Layer
Floor Screed

I'm starting from above the Concrete Slab, I don't mind putting another DPM there to make sure so that for me would be:


DPM
Insulation
Vapour Control Layer
Floor Screed


What is the vapour control layer?

 

[^woody^]

You don't need any other vapour barrier or otherwise

The DPM prevents moisture coming up, the insulation insulates, the screed can evaporate naturally

 

[sotal]

So the screed can go straight on top of the insulation??

I just found this page:

http://www.jablite.co.uk/insulation...ras/Prem-Below-Screed-Finish-installation.php


Which seems to suggest it will be fine like that, just need to tap the boards to stop the screed dripping down between them.

So it's simply:

DPM
Insulation with taped joints
and atleast 65mm of Screed
Then floor covering



Fantastic I feel like I'm getting somewhere now, I'll just go off and put a shopping list together then post it up - is it alright if you can just confirm my shopping list is OK once complete!?

Many thanks

 

[sotal]

Shopping List:


DPM - 1000 guage
http://www.wickes.co.uk/damp-proofing-membrane-1000-gauge/invt/152858/

Insulation

I can get some 75mm thick Jablite Flooring Insulation, then put 85mm screed on top.

Or I can get 100mm Jablite Polystyrene Sheet and put 60mm screed on top. Would that be OK? Would I need reinforcement?


Screed

3 parts sand to 1 part cement[/b]