Preparing a garage floor for a very basic garage conversion

[MabelEstherAllen]

I need some advice about doing a very basic garage conversion, and particularly about the floor.

I have a double garage of 5m width by 4.85m depth, which is currently set up as a carport. There is a brick back wall (2.6m high by 5m wide), and 2 side walls constructed of breeze blocks (each one sloping from 2.6m high at the back to 2.1m high at the front; and with a width of 4.85m). The front is left open. The base is concrete.

I want to turn it into a games room for the kids, so my plan is to close off the front by building an external stud wall with a single door into it, which I'll insulate on the inside, and clad on the outside. I'm then going to batten the 3 existing walls, insulate, and cover with plasterboard.

My question is about the flooring. Currently there's a concrete floor which is bumpy and dusty. It's definitely not smooth and level. I doubt there's a DPC. I was thinking that I'd first put down an epoxy DPM (something like Permacoat Pro One Coat), with some quartz aggregate scattered over. And that then I'd put down a self-levelling compound. And then, as a final surface, I'd just put down something like gym tiles.

My priority is definitely keeping my budget low.

Does this sound correct, in terms of what I'm describing with the floor? I'm a fairly experienced DIY-er, but mainly in joinery, and I haven't done this sort of work before. Do I need to put down a primer before the epoxy DPM? Can I put the primer or DPM onto a pretty bumpy concrete base (I'll obviously clean it thoroughly first). And this is perhaps a really dumb question, but should I do the floor first, before I build the external stud wall and batten, insulate etc the walls? Or should I do the walls first and then do the floor last?

Thanks so much!

Normal way to do the floor in half hearted garage conversions like this, is to build a wooden framework across the concrete garage floor. Then fix floorboards over the top, followed by your final choice of flooring on top of that.

It’s easily removed if you ever need to convert back to garage.

You can then also insulate under the floorboards if done this way, otherwise you’ll have a very cold
floor.

This is exactly what we've done ^

We've added an insulated stud wall to partition off a storage area in the front third of the space.

Built a timber frame, filled with insulation and laid pine floorboards. We're going to paint the floorboards and lay a rug over the top for additional cosiness. It'll be a boot room/office.

Ours was actually originally a room but converted to a garage complete with concrete floor in the 1960s. The floor needed raising in there anyway to bring up to the level of the adjoining room, so we took the opportunity to over compensate with extra insulation.

The problem is that, at the point around the doorway, the overall height of the space is only 210cm. I think that building a wooden framework and then floorboards on top might make the flooring too high, so that there’s not enough headroom in this part of the room.

What you are suggesting will feel freezing cold even with the floor mats. I converted my double garage but kept the back part for storage, it has a painted floor with floor mats and it keeps the drinks cold in summer.

There are two ways, the timber floor as above or just put a DPC down, Kingspan insulated panels (or any other brand but most people seem to know what a Kingspan panel is as they are found in B&Q) then sheet the floor with flooring sheets.

This video by The Restoration Couple is a good example of it and I think massively easier than leveling off the timber joists,

OP, I am confused, you are turning the car port into a games room and leaving the garage at the back?
Why not use the garage as the games room and leave the car port. Have I totally misunderstood?!

Maybe carport was the wrong word. It's basically a space that was used by the previous owner as a garage, but it has no door. It's a doorless garage. It has 3 walls (one back wall made of brick; 2 side walls made of breeze blocks) and a corrugated metal roof. But because there's no door and nothing (no wall etc) on the front side, it's open to the elements. I currently keep the kids' table tennis table in there, but it's a bit of a manky space, and when it's very windy and rainy, the rain gets in to a lot of the room.

We already have 2 properly converted outbuildings - one as a gym; one as a garden office. I don't need this space to be anything like as properly converted as those two buildings. I just want to make this particular space watertight, and to turn it a space where the kids might occasionally go and play table-tennis or fusball. So it doesn't need to be fully insulated (I'll put some electric heaters in there for winter).

Anyway, thank you for your comments. From what you've said, it sounds like it probably isn't worth me spending a lot of time on the floor, unless I'm going to insulate it properly (which I don't have the head-room to do, because of the low ceiling height). I've had another closer look at the floor, and it's not actually as rough as I thought. I think I'll just apply some Everbuild Concrete Hardener/Dustproofer, and then lay some heavy duty rubber gym tiles on top. Thanks all!