Concrete slab floor - getting it level in a single pour

[jh3141]

(Apologies for reposting this; I think I originally posted it in the wrong place, and don't seem to be able to move the post.)

I'm planning on pouring a concrete slab floor in my extension, and have been advised that it's possible to pour it in a single 100mm smooth concrete slab rather than the more traditional 100mm concrete + 50mm screed. I'm just wondering how I would get this level? I'll be pouring it on top of my DPM that will be extending up the walls, so I don't see how I can mount anything that I can use as a guide rail for a tamping bar or anything like that... any way I can think of of fixing something that's going to withstand pouring concrete around it is going to involve making a hole in the DPM, which obviously I can't do. Is there a way of doing this that I've missed?

 

[Pallatrax]

I'm no expert, but couldn't you get is pretty bob on and than pour just a self leveling compound on it, saving time and money?

Tom

 

[Norcon]

Here in the province we lay home floors the correct way.

That's laying down a sub floor unto compacted type 3 then complete the building works.
Then insulation is laid and the finished screed on top.

There is a number of advantages with this method...
1 - Allows you lay services within the insulation layer and only a weak sand/cement screed is above them so they are classed as accessible.

2 - Reduces the thermal inertia of the structure allowing faster warm up times in winter

3 - Reduces the weight pressing down on the insulation

4 - Reduces heat loss

5 - And of course is especially important with UFH as you avoid prolonged warm up periods

 

[noseall]

Single pour, power floated slabs are for individual buildings, or stand alone structures and are largely unsuitable for extensions.

As said, when building an extension, it is wiser to leave room for a screed.

 

[catlad]

Hang some lengths of 3x2" vertically and then attached a tamping rail to them.

 

[limerockconstruction]

Single pour, power floated slabs are for individual buildings, or stand alone structures and are largely unsuitable for extensions.

As said, when building an extension, it is wiser to leave room for a screed.

I concur with Noseall.

 

[Norcon]

If the OP wants to bodge it according to British regs than he might as well pour it in a single pour.
I've seen it done on occasion.

He could do it properly and follow the regs here in the province and tell his bco to go and stuff himself.

 

[noseall]

He could do it properly and follow the regs here in the province and tell his bco to go and stuff himself.

As far as b'regs are concerned, the position of the insulation is irrelevant as long as it is put in to the correct thickness and the correct details (dpm, perimeter insulation etc) are observed. We always fit it above the slab where UFH is being installed.

Whilst i agree that regarding UFH, the position of the insulation is important, i.e above the slab and beneath the screed, there is nothing to suggest that having the insulation beneath the slab is detrimental to heat loss in any way.

Your argument is flawed.

 

[Norcon]

Not detrimental but it will increase heat loss as the surface area on the wall is increased.
My arguments not flawed.

A heavyweight slab of concrete might be ok in a hot country but not the uk.

 

[noseall]

Not detrimental but it will increase heat loss.
My arguments not flawed.

Do they build cavity wall structures where you live?

 

[Norcon]

Heat travels through cavity structures.

The main advantage of the method we use here is laying the services.

 

[noseall]

Heat travels through most structures.

Do they build cavity walls where you live?

 

[Norcon]

Single pour, power floated slabs are for individual buildings, or stand alone structures and are largely unsuitable for extensions.

As said, when building an extension, it is wiser to leave room for a screed.

Why?
As in what are the logical reasons from an engineering point of view?

 

[noseall]

Why?
As in what are the logical reasons from an engineering point of view?

Because an extension usually has a knock-through.

Do they build cavity wall structures where you live?

 

[Norcon]

Because an extension usually has a knock-through.

You mean a door?
I think you're saying it would be difficult to match the two floors at the same level.

I can see no reason why not.