Single skin detached garage insulation & flooring

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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:

garage2.png


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.
 
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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
 
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
 
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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.
 
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?
 

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