Wunda joist UFH with posi-joists

[eandg]

Just come across the Wunda Joisted UFH  which on the face of it looks a good option for upstairs bathrooms (with no issues with making sure flooring is flush etc). Is there any reason this system wouldn't work with posi joists? 

[keith65]

You can`t notch posi joists to make the loops.

Edited March 31, 2021 by keith65

[ProDave]

I did similar in our bathroom and en-suite.  I threaded the pipe through the web of the joists where they had to cross over.

 

Even a very short loop in a small bathroom was a real mare of a job threading and re threading a long length of pipe through the joists.  But it is doable, just, if you are patient.  As noted do NOT even think about notching the top of posi joists.

 

I would not even consider trying on a larger room e.g. a bedroom.

[eandg]

Thanks both, given my lack of skill I'll rule that out. Any alternatives?

Edited March 31, 2021 by eandg
Typo

[Dudda]

31 minutes ago, eandg said:

Thanks both, given my lack of skill I'll rule that out. Any alternatives?

You put down the OSB or chipboard floor on top of the posi joists and then put down small battens directly over the posi joists. These battens can be notched or cut to leave gaps for the UFH pipes. Another layer of chipboard / OSB / Floorboards is placed over this. The issue is the floor will be about 50mm higher. Not an issue if you're early enough in the build.

Edited March 31, 2021 by Dudda

[eandg]

4 hours ago, Dudda said:

You put down the OSB or chipboard floor on top of the posi joists and then put down small battens directly over the posi joists. These battens can be notched or cut to leave gaps for the UFH pipes. Another layer of chipboard / OSB / Floorboards is placed over this. The issue is the floor will be about 50mm higher. Not an issue if you're early enough in the build.

We don't have the kit up yet... would we just need to lift the full first floor up 50mm or is there some other solution? 

[Dudda]

1 hour ago, eandg said:

We don't have the kit up yet... would we just need to lift the full first floor up 50mm or is there some other solution? 

By kit I presume you mean timber frame? Are you still in design stage or has manufacture started?

 

If still at design stage you've a few options. You can ask them to check the loadings and span and design the posi joists to take the load of a 50mm liquid screed at first floor. You can have your underfloor heating pipes in this.

 

Need to know what stage exactly of the build you're at so we can give other options.

[ProDave]

1 hour ago, eandg said:

We don't have the kit up yet... would we just need to lift the full first floor up 50mm or is there some other solution? 

11mm OSB to support the UFH, 25mm battens following the joist lines (to allow you to notch the battens for the UFH pipes to pass) , 22mm chipboard floor = only 36mm higher finished floor than just the flooring straight onto the joists.

 

The critical area will be internal door openings, frame those a bit higher.  You only need to raise the whole 1st floor frame if you think losing 36mm headroom is going to make the ceilings too low.

 

With a bit more work you could set the OSB as strips between the joists with their top level with the top of the joists so your floor is only then raised by 25mm.

[eandg]

22 minutes ago, Dudda said:

By kit I presume you mean timber frame? Are you still in design stage or has manufacture started?

 

If still at design stage you've a few options. You can ask them to check the loadings and span and design the posi joists to take the load of a 50mm liquid screed at first floor. You can have your underfloor heating pipes in this.

 

Need to know what stage exactly of the build you're at so we can give other options.

Just about to go into detailed design and engineering with (SIPs) kit manufacturer. 

[eandg]

22 minutes ago, ProDave said:

11mm OSB to support the UFH, 25mm battens following the joist lines (to allow you to notch the battens for the UFH pipes to pass) , 22mm chipboard floor = only 36mm higher finished floor than just the flooring straight onto the joists.

 

The critical area will be internal door openings, frame those a bit higher.  You only need to raise the whole 1st floor frame if you think losing 36mm headroom is going to make the ceilings too low.

 

With a bit more work you could set the OSB as strips between the joists with their top level with the top of the joists so your floor is only then raised by 25mm.

Thanks. First floor is largely vaulted and we'd designed the walls to be 2450mm above chipboard. 

[Nickfromwales]

Just fit 150mm strips ( or whatever the remaining gap will be between the omega shaped pipe troughs ) of 18mm plywood glued and screwed directly on top of the pozi’s, then for alu spreader plates ( 2mm ). Load with pipe ( removing sections of plywood to perform the crossovers ) and then you’re just ffl + 20mm.

 

Edited March 31, 2021 by Nickfromwales