Garage floor

[Patters1978]

Hi

I'm looking for some advice on what to do with a garage floor, the aim is to have the room as a summer room. The project is not mine but the farther in-laws.

He wanted to put floor joists down bit of insulation in-between the OSB boards, but after being around today to help him level of it seems as tho he would only have enough height for around 140mm joists over a 3m span?
I suggested this wouldn't be enough to instead try and level off the floor then do a 50mm PIR boards with OSB

Any suggestions the floor slopes towards the white patio door around 80mm and it has a big pit
I was think of using sand to level out the floor?
Obviously have to fill the pit in some way

 

[jeds]

I wouldn't be comfortable with sand levelling. Sand will shift around and inevitably create a void. Given the state of the floor and some difficult in levelling it adequately I would advise a timber floor but support the span with levelling cradles or timber blocks.

 

[Patters1978]

I wouldn't be comfortable with sand levelling. Sand will shift around and inevitably create a void. Given the state of the floor and some difficult in levelling it adequately I would advise a timber floor but support the span with levelling cradles or timber blocks.

The 140mm joist would be sitting directly on concrete in place doesn't it need some breathing room?
The only other thing I have read is keying down some MOT with concrete and then building it up with that? Around the edges where there is no supporting wall he could just build a little retaining wall?

 

[jeds]

Use 100mm joists.

 

[mrrusty]

Yes, I would use 100mm joists too. You could either batten the floor lengthways to get it level and cross joist or pack the joists individually or a bit of both. Assuming the floor is solid, which it looks like it is, it will be fine. Once you have the joists down, you can insulate between if you want to.