Single skin detached garage insulation & flooring

[Pollywantacrackwhore]

I'd like to insulate my (concrete) garage floor. It's single skinned so I will seal the concrete (1st coat sealant, 2nd coat sealant + SBR). I will then use tanking slurry on the walls (1st coat slurry + SBR, 2nd coat just slurry). I expect a little slurry left over so I will use that to re-coat the floor (3rd coat). I expect that would take care of any moisture coming in.

I then want to insulate the floor, but what are my options, assuming it's even worth it? This is the floor plan:

My garage is 3.14m x 5.95m so I believe my PA ratio (permiter / area, or ((3.140+5.953)*2)/(3.140*5.953), is 0.97. That means to get a U value of 0.22 I will need 100mm of insulation. I have 25mm from concrete to door level. I can probably push it to 300mm (that being the final floor level).

Firstly, is it even worth it? I plan to live here for the next 20+ years and I just want the floor to not be freezing in the winter. I will insulate the walls and roof, and have a heat source in the garage. Should I even bother with the building-regulation level of insulation?

Secondly, if it's worth insulating it, what are my options? I believe I need insulation then some sort of structural board on top (I'm leaning towards plasterboard to keep it thin), and cover it with vinyl or some-such material.

Any ideas and recommendations welcome.

 

[motorbiking]

if you aren’t bothered about building control the 50mm celotex “glued” with plasterboard foam and standard plasterboard (glued with the same). Don’t go with the batten route. Will give you a U value of around 0.25. Which was pretty good not so long ago. You’ll be able to heat with a 2kw fan heater

 

[Pollywantacrackwhore]

if you aren’t bothered about building control the 50mm celotex “glued” with plasterboard foam and standard plasterboard (glued with the same). Don’t go with the batten route. Will give you a U value of around 0.25. Which was pretty good not so long ago. You’ll be able to heat with a 2kw fan heater

Sorry, I meant I have 25mm to work with (corrected in post now), so 50mm celotex PIR isn't feasible.

Maybe a couple of layers of this - https://www.ecohome-insulation.com/...y0tflrh57_BZRloCrLKmtFSkipxElbYaAlpVEALw_wcB?

That would be 8mm thick

 

[freddiemercurystwin]

What will you be using the garage for?

 

[motorbiking]

50mm on the walls and roof and as much as you can manage in the floor. What do you plan to do with the garage door?

Heat reflective foam/foil will provide no benefit at all.

 

[Pollywantacrackwhore]

50mm on the walls and roof and as much as you can manage in the floor. What do you plan to do with the garage door?

Heat reflective foam/foil will provide no benefit at all.

What will you be using the garage for?

Sorry, thought I put this - I want to use it as an office / workshop (no sawing, just electronics / minor hammering / etc.) - essentially a man-cave that I can do some work in. I'll chuck some rugs down.

I plan on doing the walls and celing, and I'll have a heat source in there. I just don't want cold feet.

@motorbiking - why do you think there will be no benefit to insulating the floor? From what I've read, it's important to do the floor?