Size of gravel under insulation in floor???

[DrKassler]

What size/type of gravel should we buy to place under the insulation for our future concrete floor with hydronic underfloor heating???? Maybe the size doesn't matter, or does it ?

/DrKassler's secretary...

 

[jon_h]

You should probably use macadam and not singel; macadam can be packed much better and reduces the risk of settling later. I think fraction 8-16 or 11-16 might be appropriate.

 

[Mats]

I have learned that it should be 8-16 macadam. At least 10 cm thick layer

 

[DrKassler]

Hi!

The only thing they had near the pit was 4-8 macadam... Can we use that too or will we mess up then?

Best regards,
/C

 

[Stoia]

Hello!
I think you are making a mistake because 4-8 makadam is more similar to sand than gravel. 8-16 transports moisture and water away much better if such should appear under the foundation.