Levelling current concrete floor

[TheMick]

Hi all, 

I've got an 11mtr sq floor in an outbuilding I've converted into a livable space. The floor is now the only outstanding work. 

 

Unfortunately whoever laid the concrete base has it relatively square running the length but the width is on a slope where on the centre its 40mm and one corner is 35mm and the other 20mm.

 

Im wanting to put electric underfloor heating mats down so need to level the floor and then put down 7-10mm depth of self level on top of the mats. 

 

Does anyone know If it's possible to sort the levelness with concrete on top of concrete for the 40mm then just use the self level compound on the 7-10mm that goes on after the heating mats are put on the concrete. 

 

Need to keep costs down as her indoors is complaining about the cost of 20 plus bags of compound to do it all with just that. 

 

Any help is greatly appreciated. Thanks

Edited August 17, 2020 by TheMick

[nod]

You could seal the floor with SPR

Then use Grano to level out the floor Then a thin layer Of self leveling on the finer stuff 

I’ve used Grano on all sorts 

Cheap and sets like iron 

[PeterW]

Is there any insulation in that make up of the floor ..? If not, UFH mats will be a waste of time as it will just heat the concrete. 

[TheMick]

20 minutes ago, nod said:

You could seal the floor with SPR

Then use Grano to level out the floor Then a thin layer Of self leveling on the finer stuff 

I’ve used Grano on all sorts 

Cheap and sets like iron 

First I've heard of Grano. 

 

Do you reckon it will be OK where it thins out across the other side of the floor? 

 

Do you just mix it with water? 

 

Thanks for that. 

[TheMick]

21 minutes ago, PeterW said:

Is there any insulation in that make up of the floor ..? If not, UFH mats will be a waste of time as it will just heat the concrete. 

Hi Peter, I did see those thick mats you can put down before the heater mats but haven't fully thought that bit through yet to be honest. 

Bit lost as only really laid concrete before not levelling a previously laid floor. 

 

Thx

[Nickfromwales]

10 minutes ago, TheMick said:

Hi Peter, I did see those thick mats you can put down before the heater mats but haven't fully thought that bit through yet to be honest. 

Bit lost as only really laid concrete before not levelling a previously laid floor. 

 

Thx

Use tile insulation backer boards to level the floor, and then you get a good method to both level and insulate the slab prior to accepting the finished floor covering. What finish do you have intended? 

[Nickfromwales]

I used them on this job, which ad an un-insulated 150mm concrete slab.

 

 

The insulation boards run up to the edge of the shower former, and insulate the UTH wire from the sub-floor below. Not great, but shit-loads better than heating the concrete floor with an UTH setup !!!!

You'll be looking about 40p in the pound going south if you carry on with your proposal.

Edited August 17, 2020 by Nickfromwales

[TheMick]

12 hours ago, Nickfromwales said:

Use tile insulation backer boards to level the floor, and then you get a good method to both level and insulate the slab prior to accepting the finished floor covering. What finish do you have intended? 

Thanks for the response. 

 

Tile insulation backer boards to level the floor instead of Grano? Tah

[PeterW]

15 minutes ago, TheMick said:

Thanks for the response. 

 

Tile insulation backer boards to level the floor instead of Grano? Tah

you can just use sharp sand and a DPM under them, or a dry sharp sand and cement mix to level the holes. Then the tile backer board on the top. 

[Nickfromwales]

1 hour ago, PeterW said:

you can just use sharp sand and a DPM under them, or a dry sharp sand and cement mix to level the holes. Then the tile backer board on the top. 

If fitted properly, the insulated boards can be used as DPM  

[Nickfromwales]

From the Marmox WS;

 

Quote, "The unique patented surface of Marmox Multiboards allows tiles of a much heavier weight to be safely and securely fixed to walls. Being completely impermeable to water, they are doubly useful in tiled areas prone to moisture such as kitchens and bathrooms where they will act as a moisture barrier protecting the walls and floor. Multiboards can be used to insulate and waterproof walls, floors and ceilings and noticeable benefits will be gained by using any thicknesses of 10mm and above."

Edited August 18, 2020 by Nickfromwales

[TheMick]

5 hours ago, PeterW said:

you can just use sharp sand and a DPM under them, or a dry sharp sand and cement mix to level the holes. Then the tile backer board on the top. 

By dry sharp sand and cement mix to level it beneath the backer boards do you mean with no water at all? Thx

Edited August 18, 2020 by TheMick

[PeterW]

Yes - there will be enough moisture in the sand for the cement to go off. Makes it easier to level this way. 

[TheMick]

Dry sharp sand and cement ratio mix put down dry then tile backer boards then the underfloor heater. Then self level compound 6-10mm on top of that. Then can either tile or lay laminate? 

[PeterW]

6:1 sand cement will do it. Just lay tiles straight onto the heater element in adhesive. 

[Nickfromwales]

If laminate flooring, then a suitable foil kit instead of a wire, and either lay straight onto the boards, or level first and then lay the foil + laminate / engineered floor. 
Any leveller under the foil needs to be 100% dry before being covered!!

[TheMick]

On 18/08/2020 at 18:50, PeterW said:

6:1 sand cement will do it. Just lay tiles straight onto the heater element in adhesive. 

Hi Peter. 

How do work out how many you would need? 

I can work out the cubic meters where I'm guessing you half the 40mm depth as it is essentially a triangle (to level the angled floor). 

But after that do you use a paving or patio calculator online? Thx

[Ferdinand]

if it is to be liveable do you not need to meet Building Regs?

 

(Sorry)

[TheMick]

1 minute ago, Ferdinand said:

if it is to be liveable do you not need to meet Building Regs?

 

(Sorry)

It's not going to be a regular live in house. Just something that will have the comfort of the house and if you felt like it could spend the entire night in there and sleep in the warm and dry. 

 

It's totally detached from the house about 8mtrs away. 

[Nickfromwales]

1 hour ago, TheMick said:

It's not going to be a regular live in house. Just something that will have the comfort of the house and if you felt like it could spend the entire night in there and sleep in the warm and dry. 

 

It's totally detached from the house about 8mtrs away. 

You can use a small fan heater to kick start things if you’ve ever forgotten to turn the UFH on so no big problems there. 

[TheMick]

59 minutes ago, Nickfromwales said:

You can use a small fan heater to kick start things if you’ve ever forgotten to turn the UFH on so no big problems there. 

Great that's good to know for the future. 

I'm sort of stuck as to how to calculate how many bags of sand and cement I will need. Do you know the calculation? 

 

I get the cubic meters part but is there an online calculator to tell you how much of each total you need? Cheers

[PeterW]

28 minutes ago, TheMick said:

Great that's good to know for the future. 

I'm sort of stuck as to how to calculate how many bags of sand and cement I will need. Do you know the calculation? 

 

I get the cubic meters part but is there an online calculator to tell you how much of each total you need? Cheers

what area are you trying to level ..? Room dimensions and how far out of level is it ..??

[TheMick]

24 minutes ago, PeterW said:

what area are you trying to level ..? Room dimensions and how far out of level is it ..??

It's 4.5mtrs x 2.4mtrs

 

Worst area is 40mm so cubic meterage is 0.432 m3 but I was thinking you would half this as the space to fill is like a triangle going from 0 (level) down to 40mm.

 

Thx

[PeterW]

So you’ve got about 0.25 cubic metres, which if that was sand would be about 350kg of sand (it’s about 1.6 tonnes to the cube) so I would get 14 bags of sand and 2 bags of cement to be on the safe side. 

[TheMick]

Nick and Peter how do these marmox boards perform if after you have put your floor you then want to put a weighty item on the floor surface like a wood desk etc. 

I only ask as I'm now thinking of using the sand and cement dry method first then after it's set putting the 10mm marmox boards down. 

 

Foil elec UFH (not where the desk will go) then laminate straight on top. 

 

That sounds like the backing board will be taking all the weight. 

 

Cheers.