Garage floor construction with underfloor heating

Hello everyone,

great forum here, I have already read quite a bit! A personal introduction thread is coming, I first need to find my way around all the great posts!

I would like to get a few more opinions on how to best design my floor structure!

The planned object will be a storage room of just under 110m²! The floor area is rectangular, 13.5m x 8.5m! Used for storing vehicles and trailers, heated!

The current building will be demolished in the next few weeks, the required area will be cleared. Our groundwater level is high; after digging 1.5m, groundwater appears!

My idea so far: I will have the entire area excavated to a depth of -70cm. The first 30cm will be backfilled with 0-63 crushed stone. On top of that a finer, permeable layer with 0-32 crushed material. On top of that, I wanted to lay a PE foil and cover the entire area with 10cm XPS Styrodur boards. On top of that follows a 30cm thick concrete slab, which I will have poured with high-quality ready-mixed concrete depending on your recommendations, possibly also executed as WU (waterproof)!

Here is the sketch:



I am interested in your tips and experiences with the slab under a storage hall / storage room!

On the slab, later an aluminum-coated bitumen membrane will be installed for sealing against the masonry; I planned this with 30cm concrete formwork blocks. The walls are around ~360cm high all around, externally clad with 8cm full thermal insulation with XPS Styrodur boards. On top comes a foam trapezoidal sheet roof with about 16kg/m².

This is currently my plan; the submission plan has already been approved by the master builder and is with the municipality for review before the building negotiation.

I need your experiences with the floor structure!

Specifically, I am interested in the following:
Installation of underfloor heating - does the 120m² slab need to be equipped with expansion joints? If yes, what are the rules for this?
30cm concrete slab with AQ50 reinforcement mesh double layer, or should I order fiber concrete straight away?
Is the idea with the floor structure underdimensioned in detail?

Many thanks for your ideas,
best regards from Austria,
Robert

Just under a week and no response, are any details missing? I would appreciate it if you could write something about it so that I can plan properly! Thank you very much!!

Your questions cannot be answered by laypeople and this is a forum mainly by and for laypeople. You need a civil engineer or architect ...

I just wonder why someone would want to heat a garage .... vintage car? luxury sports car? A normal garage for normal cars, which are used normally, is better ventilated but not heated. You certainly know that .

But it seems important, judging by the frequency of the exclamation marks

Hi,
Heated screed may be max 40 sqm, after that expansion joints are required.

A structural engineer must calculate the floor slab anyway. In industrial buildings, a lot of fiber concrete is used. However, it has the disadvantage that for absorbing high point loads (roof columns, lifting platform, steel platform for storage, etc.) you still need foundations in the floor slab. In other words, you have to plan beforehand where you want what and then reinforce the floor slab accordingly. Without reinforcement, it usually only withstands point loads of 15-20 kN, which is not enough.

The question of why one would want to heat a garage is, however, not entirely unreasonable. If you want to work in there occasionally, I would use these "water-air heat exchangers" that are hung from the ceiling. And also section off the work area and only heat that when needed. Installing underfloor heating everywhere is quite overkill in this case.

Best regards,

Andreas

I don’t know how it is in Austria, but as far as I know, a building that is designated and approved as a garage is not allowed to be used as a workshop, etc. Additional requirements would have to be met in that case.

And if a garage is fully heated, such questions regarding usage will probably arise.