Concrete or self-leveling compound

[Snabelhund]

Hi, I'm considering what's best. I've installed waterborne underfloor heating on the ground floor. I'm about to embed the loops and am pondering whether to use screed or concrete.

The conditions are as follows: the area is about 30 sqm and can be divided into 2 pours, one 10 sqm and the other 20 sqm. I need to rise up 4 cm to get good coverage on the pipes. The smaller area is a hall where the only entrance to the house is located, which means we have limited possibilities to close this passage. 24–48 hours is obviously okay.

Regardless of the choice, the final irregularities will be leveled by professionals for maximum flatness.

Is it worth investing in concrete despite the longer drying time? The hall is to have tiles, so it's necessary to consider that one must wait until the concrete is completely dry before this can be done (3 months?). Are screed battens needed, or can relative flatness be achieved in another way?

I have access to a cement mixer for the concrete but not a screed pump; is it possible to level 30 sqm or 20/10 with a bucket and paddle?

The concrete costs about half as much as the self-leveling compound, but money is not the only deciding factor; the end result and ease are prioritized.

What does the expertise at Byggahus say?

 

[falkn]

Bring in someone to do it for you. 4 cm on 30 m2 is around 95 bags. You can't hand mix it and get it right.

 

[Snabelhund]

Bring in someone to do it for you. 4 cm over 30 m2 is around 95 sacks. You can't mix it by hand and get it right.

That was the original plan, but vacation times and corona make it insanely difficult to find someone who can do this at relatively short notice. Considering if a concrete truck is the solution.

 

[C.Lundin]

You say that "a professional" should redo what becomes bad. Then let someone who can perform it directly so the same job doesn't have to be done twice.
But it will probably be difficult to find someone who agrees to cast 40 mm concrete, even if it were without loops... It's leveling compound that's needed.

 

[Snabelhund]

You say that "a professional" should redo what is bad. Then let someone who can do it directly so the same job doesn't have to be done twice. But it will probably be difficult to find someone who agrees to cast 40 mm concrete, even if it were without coils... It's leveling compound that's needed.

I had hoped that the one who is going to "top off" with leveling would want to do the whole casting, but unfortunately, that wasn't possible, so I got the tip to level most of it myself with the help of a 200-liter barrel. However, I feel uncertain whether I can manage to level this myself. Hence the question if it's easier with concrete. Follow-up question: why leveling compound and not concrete?

 

[sixten88]

If you absolutely have to do the work yourself, I would have:
1. Primed and sealed for the pour. It's easy for it to detach from the substrate otherwise.
2. Ensured that the underfloor heating is anchored, filled, and that there's rebar over it.
3. Poured with self-compacting concrete and stone chips of max 8mm.

What type of flooring are you planning to use? If it's parquet or tiles, it's sufficient to grind off the peaks the next day.

 

[Snabelhund]

If you absolutely must do the work yourself, I would:
1. Prime and dowel for the overlay. Otherwise, it's easy for it to detach from the substrate.
2. Ensure that the underfloor heating is anchored, filled, and that there's reinforcement over it.
3. Cast with self-compacting concrete and use aggregate with a maximum size of 8mm.

What kind of flooring are you going to have? If it's parquet or tiles, it's enough to sand down the peaks the day after.

The underfloor heating is on foam plastic and anchored with Lks system for this. I guess you only dowel when it's concrete against concrete? There's reinforcement on top of the pipes. I will have tiles in the hallway, the flooring in the living room is not yet decided.

 

[sixten88]

How is the entire floor construction?

 

[Snabelhund]

How is the entire floor construction?

From the bottom up, erge joist at the bottom, 10 cm eps, 5cm Xps, 16mm pipes in pipe holding rails, reinforcement. Here we are now, and this will be cast in.

 

[falkn]

From the bottom up, install decking at the bottom 10 cm eps, 5cm Xps, 16mm pipes in pipe holder rails, reinforcement. This is where we are now, and this needs to be cast in.

It's too thin to pour with concrete in my opinion. In that case, SKB with 4 mm aggregate as the largest grain, meaning nothing you mix yourself. This should be floated with a pump; otherwise, it won't turn out well.

Sure, you can spend a whole day stirring filler, but it will set too quickly and won't be flat.

 

[Snabelhund]

Suppose I divide the surface and float, is it more feasible? For example, if I split the surface into 10/1010 or 10/20 sqm?
I'm trying to find a plaster pump in the Stockholm area, but it seems tricky to get hold of...

 

[sixten88]

I had bought the concrete and the delivery with fixers and cast everything at one time. However, you can section off the different rooms to more easily lay out at the level.