Floating floor, what can be done...

[da3533]

Hello

I cleaned up my garage floor and wanted to lay down 100mm PIR insulation, TG chipboard... It is a concrete base floor at the moment with dips. See picture attached.
I have read to put KILN dried sand on the areas....

Any suggestions?

 

[George_engineer]

You should use a liquid floor levelling screed. Sand could work but I think it would be a bit of a nightmare. Usually sand is to level beneath a concrete slab which will hold it in place... one knock from the insulation during installation and the sand won't be level anymore.

Will need a DPM under the insulation and VCL above it as well.

 

[ETAF]

i had a similar issue in a ground floor house - daughters and also my cloakroom and kitchen
NOTE
I'm Just a DIYer

The kitchen had quite a few central heating small bore pipes - 6 going through and they had used sand to bed/fill that area

My bungalow is ALL suspended floor on concrete
The cloakroom when i lifted the old rotten floor it was all out of level and a big dip in the middle they had filled with sand, and quite a large slope from about a meter in to the back wall , so i got some self levelling screed from screwfix and made that all level - very easy to use - and then used kiln dried sand where the pipes went between the insulation i put down , before laying marine ply on top
to be honest the sand was a nightmare to get level and stay level - just in the small gaps between the insulation and the pipework ....... went everywhere
I had orginally thought of just filling the void and slope with sand like had been done before - but the screen was very easy to do and use.

I also Used a lot of self leveling screed in various places at my daughters house before we laid a laminate floor - again very easy to do , we lifted the entire ground floor , which had tiles and a slight change in levels between rooms - and so we screeded in a lot of areas and made a very gradual slope , so the laminate flooring and the underlay was as level as possible.
worked well, with children running all over it for a few years. they lifted it all up last year when having an extension built and a relayout of the ground floor and it was all still in good condition

 

[da3533]

i had a similar issue in a ground floor house - daughters and also my cloakroom and kitchen
NOTE
I'm Just a DIYer

The kitchen had quite a few central heating small bore pipes - 6 going through and they had used sand to bed/fill that area

My bungalow is ALL suspended floor on concrete
The cloakroom when i lifted the old rotten floor it was all out of level and a big dip in the middle they had filled with sand, and quite a large slope from about a meter in to the back wall , so i got some self levelling screed from screwfix and made that all level - very easy to use - and then used kiln dried sand where the pipes went between the insulation i put down , before laying marine ply on top
to be honest the sand was a nightmare to get level and stay level - just in the small gaps between the insulation and the pipework ....... went everywhere
I had orginally thought of just filling the void and slope with sand like had been done before - but the screen was very easy to do and use.

I also Used a lot of self leveling screed in various places at my daughters house before we laid a laminate floor - again very easy to do , we lifted the entire ground floor , which had tiles and a slight change in levels between rooms - and so we screeded in a lot of areas and made a very gradual slope , so the laminate flooring and the underlay was as level as possible.
worked well, with children running all over it for a few years. they lifted it all up last year when having an extension built and a relayout of the ground floor and it was all still in good condition

Thanks. i didnt want to use screed but i will have to then seems simpler and will make it easier in the long run

 

[ETAF]

i didnt want to use screed

any particular reason why not ????

 

[da3533]

any particular reason why not ????

sometimes i would think 2 bags enough then realize i need 2 more and by the time i get the bag, it drys a bit... i will have to bag 4 at once...

do you have to use a trowel or straight edge?

 

[ETAF]

i did in some cases , but when i did the cloakroom, (on my own) and an old kitchen it all flowed and levelled nicely on its own - but we (2 of us doing the ground floor) had various trowels and straight edges on hand when we did the ground floor , and to get the last bits out of the bucket - and particularly where we filled a sloping area to get level
had some of the flexibuckets for mixing - used them a lot not only for screed but also concrete and tile adhesive mixing.

and a mixer head to go into the drill

sometimes i would think 2 bags enough then realize i need 2 more

Yep, been caught out like that in the past, with postcrete.
but I usually buy from screwfix now and I buy a few more bags then i think needed , as screwfix are great about taking items back , i think you have 30days , but usually returned within a week

i have purchased a lot of items from screwfix, I think i may need when doing jobs - incase it goes wrong or need extra , and then I simply take them back unused. We dont have the 60min sprint service here.

 

[da3533]

thanks

there is two types in Screwfix.
/no-nonsense-cement-based-levelling-screed-20kg
Cement base
or
no-nonsense-floor-levelling-compound-20kg

What did you use?

 

[ETAF]

as i say just a DIYer - so may not have made the right choice
I used

Mapei Ultraplan 3240 Self-Levelling Compound 25kg - Screwfix

Order online at Screwfix.com. Fibre-reinforced self-levelling compound. For use on new or existing concrete, screeds, stone, ceramic tiles, old and new timber floors, parquet and plywood. Covers approx. 6m² at 3mm thick. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

1) i know Mapei from the past and was a good brand and 2) fibre re-inforced
but no expert on choices . also it was much cheaper when i used around £18 and also on a deal

 

[23vc]

I’ve done it with sand (building sand not kiln dried) and it worked fine. Use a long straight edge to get it bang on. It’s not going to go anywhere once the floorboards are on and glued together on top of the PIR.

 

[da3533]

Ive layed the DPM and PIR boards. do i really need a vapour barrier over the top of the PIR too??

 

[George_engineer]

Ive layed the DPM and PIR boards. do i really need a vapour barrier over the top of the PIR too??

Yes. Unless you've taped the boards and the foil is intact.

The idea is you stop warm moist air (remembering that warm air can carry more moisture than cold air) permeating through into the insulation layer and condensing against the dpm. If that happens it'll be trapped and will never dry out.

 

[robinbanks]

If it were a timber frame house wall sure, but would I bother for a garage floor? No..

 

[George_engineer]

If it were a timber frame house wall sure, but would I bother for a garage floor? No..

I don't care, not my house! But one thing is for sure, water will always find a way of creeping around and bugs, mold and nastiness like to grow wherever these is water.