Garage with lightweight aggregate blocks + polystyrene and upper floor (picture).

[jagakatt]

I'm about to build a garage with an upper floor. After reading lots of threads about aerated concrete and lightweight expanded clay aggregate (LECA), the choice has now fallen on LECA blocks.

Could it be a good construction with 19cm of LECA plus 10cm of polystyrene with plaster? I imagine that this should provide a reasonably well-insulated garage wall. Some parts of the long sides of this extension will be below ground level by 2/3.

Surely no air gap is needed between the LECA and the polystyrene? Both materials are inorganic. The garage will be kept reasonably warm, and a wet car will only be there occasionally. The walls of the "apartment" above will get 280mm of insulation; I hope that's more than enough with the new requirements for this extension (15.6x8m in Gothenburg)

 

[Jwberg]

Hello,

I have done something similar. In my case, partially underground with Lecawalls (25cm).

My solution was pordrän/equivalent below ground and above ground I accept that insulation is moderate. The wall was plastered on the outside.

A suggestion from the bricklayers was to fill up with Lecakulor instead of pordrän and gravel, but it became rather expensive.

Best regards,
Jonas

 

[jagakatt]

My thought was to have something like plaster and 100mm of foam insulation on the entire foundation and then a Platon mat or similar on all the parts that end up underground.
There seem to be at least a hundred ways to do it wrong, and at least a hundred material choices that are wrong if you follow the threads here.
I don't want to build any risk construction. But of course... even if you do it right today, it might be a risk construction in a few years. :- (

 

[Jwberg]

It is not easy. I was also hesitant but concluded that pordrän's solution seemed reasonable. See Isodrän (variant/competitor) for insulation values for different constructions. I don't have a moisture barrier in the cross-section [inside-plaster-wall-slurry-prodrän-geotextile-gravel], and so far I haven't seen any issues on the inside (only 1½ years, to be fair). I just painted with asphalt at the bottom.

My view was that pordrän/equivalent provides roughly the same insulation in the underground case as polystyrene would have done. However, polystyrene feels tricky underground (no drainage).

I can mention that I have a section of the wall (against the earth cellar) that doesn't have any insulation board. There, the masons applied a "waterproof" slurry mortar, and on the outside, I painted with asphalt all the way up to the ground. That works too.

Also, keep in mind that the wall must withstand the ground pressure. My masons cast some concrete pillars in my wall.

I must also give a thumbs up to the size of the build!