Min Depth of Concrete/ screed on oversight + Drying tim

[champagnecharly]

I need to level the oversite. Can somebody tell me what the minimum allowable concrete that can be placed on oversite is?

Also how long should it be left before placing EPS/XPS over the top? On top of insulation will go UDF screed and then concrete microtopping.

Regards

 

[noseall]

I need to level the oversite. Can somebody tell me what the minimum allowable concrete that can be placed on oversite is?

A typical floor detail asks for (min)100mm of concrete.

Also how long should it be left before placing EPS/XPS over the top? On top of insulation will go UDF screed and then concrete microtopping.

I have no idea what this lot means.

A typical UFH floor detail would be...

100mm compacted hard core.

25-50mm sand blinding (compacted)

1200 gauge polythene tied into DPC

100mm concrete.

80-100mm Celotex/Kingspan/Ecotherm or similar PIR foam board insulation.

Another layer of polythene or tape joints.

UFH fixed to insulation

75mm (min) floor screed.

 

[champagnecharly]

Thanks.. I dont think i was clear enough..

This is a refurb. The existing oversite is sloped. I want to level it into 600 wide terrace like formations. On which different thickneses of polystyrene insulation boards (EPS expanded or XPS extruded) will be applied that will then bring the overall floor to one level. the UFH pipes will be laid on top. (god only knows where UDF came from)..

So the question is... the existing oversite is there. i intend to put a tapered thickness of concrete/screed. that will then bring the floor level. What is the min thickness I can go .. ontop of oversite?

How long should it be left to dry given polystyrene will be placed over the top.. my concern is that polystyrene especially extruded is not very breathable. So could if laid too soon make the base sweat.

By micro topping i meant: "a polymer modified micro cement based material that coats concrete, wood, metal and even glass to replicate and feel like traditional polished concrete or cast concrete floors. "

 

[noseall]

In one sentence you are saying that you will fit differing thicknesses of insulation to bring things level then in another you are asking about differing thicknesses of screed to bring things level.

I was confused before, now I'm befuddled.

 

[champagnecharly]

Thats exactly right. Floor is currently sloped from 1.1m to 400mm.

Step 1
Screed/ concrete to bring to terrace levels 600 wide. i.e a series of steps with 600mm tread from front to back each of which is horizontal

Step 2
Then Insulation laid to bring complete floor level/ horizontal.
no more steps and no more gradient.

 

[theprinceofdarkness]

I am also confused. If your minimum depth is 400 mm, then allowing for the conventional floor make up, you need 275mm of depth. So you fill everywhere to FFL-275mm- floor thickness with compacted hardcore, then lay a conventional floor. So that allowing for your floor finish ( 12mm?), you need 400 -287= 113 mm at the top of the slope and 110 - 287 = 723mm at the bottom.
Frank

 

[noseall]

Step 1
Screed/ concrete to bring to terrace levels 600 wide. i.e a series of steps with 600mm tread from front to back each of which is horizontal

This is the bit I'm not getting....?

 

[champagnecharly]

Hopefully a drawing will explain better.

Top layer is screed
Red/maroon is insulation
bottom blue yellow is screed/ concrete in terrace formation.

Untitled

• champagnecharly
• 2 May 2015
• 1

 

[theprinceofdarkness]

If that drawing is roughly to scale at the bottom of the slope you will have 600 mm+ of insulation. This will settle/compress at a different amount to the 100 mm bit at the top of the slope. The top surface of the floor will either tilt or crack due to this unless reinforcing mesh is used. I don't like it
Frank

 

[champagnecharly]

Thank you for pointing that out... I really dont know why I hadnt thought of the compression factor.
The drawing is not to scale.. It was just knocked up quickly to try and help visualise the varied levels.
The thickest insulation slab are 350mm and not 600 as the. There would also be a 200mm step (the length of the house) between front and back of property.. (not previously mentioned as not to distract) So there wouldn't be as many terrace levels to bring to horizontal.

Its hard to gauge exactly what will be needed or to draw to scale as floor is still down and tons of the nasty blue and brown stuff is under the boards and all mixed in with hardcore and plaster.

You mentioned reinforcement. Given the max depth of insulation is 350mm, what would your thoughts be on mesh required? And would it satisfy your concerns?