Post on existing concrete slab?

[Dejvan]

Hello,

I'm considering enlarging a staircase opening to an L-shape (it's straight today) and I'm wondering if it can be solved with a post at the staircase's turn to support the cut floor joist. But can you place a post on the existing slab?... 10cm concrete slab with underfloor heating.

 

[ricebridge]

Just as long as you don't install it on a floor heating loop then...

 

[Dejvan]

As long as you don't mount it on a floor heating loop then...

As long as you don't mount it on a floor heating loop then...

It's waterborne floor heating in the slab, so I should try to locate that loop. Dumb question maybe, but what is the danger if the post were to end up on a loop? Do you mean the slab is weaker there?

 

[ricebridge]

It's a waterborne underfloor heating in the slab, so I'll have to try to localize that loop. Maybe a dumb question, but what’s the danger if the post accidentally ends up on a loop? Do you mean the slab is weaker there?

There is a high risk that the post will puncture the loop, or that you will do it during installation.
The strength is probably poorer there, but what’s worse is that you'll get a local heating on the post material right there, and that's rarely good.

 

[Wes71]

Depends entirely on how much load the post will carry. Also, it might not be optimal to have underfloor heating coils under a bearing post.

 

[Pumba]

It's hard for me to imagine that it makes much of a difference whether there's a loop underneath or not, that the load would be so great from a post supporting a floor joist that it would break the floor heating loops seems like an incredibly small risk.

 

[justusandersson]

I think it's a sensible solution to place a post as support for the cut beam. I agree that it's appropriate to avoid the heating pipes to prevent unnecessary heating of the post. There's hardly any structural integrity problem. Standard concrete with 30 MPa compressive strength (just over 300 kg/cm2) withstands a lot. A 90x90 mm post can bear 24 tons to reach the concrete's limit, provided that the post and the slab's foundation can handle it.