How to mount an external door when using an insulated slab?

[zzPaulzz]

Hi everyone.  I'm working on the detail for my entrance doors.  My slab is an insulated structural raft with XPS300 upstands that will join with the MBC Twin Wall frame system.  The doors will sit in the middle of this wall. My modelling indicates that the door thresholds will be mostly, if not completely, resting on the XPS upstand which doesn't seem like a good idea.  This can't be a new problem so can I ask how you have solved this? 

 

[Mr Punter]

Can you screw a metal angle to the back of the threshold that rests on the top of the concrete?

[Iceverge]

Cut out some of the XPS to allow the door frame to be partially supported by the concrete 

[JohnMo]

I would be tempted to cut way EPS, at threshold. Make a channel to drop Compacfoam (60 to 70mm wide and about 100mm deep) in and then bolt to the concrete. That would give you something structural to rest the door threshold on, it could then be screwed to the Compacfoam. Back fill the gaps with expanding foam and cut back with dried.

[Nick Laslett]

This sounds a bit similar to the topic 3 weeks ago about insulated raft and door threshold. 
 

 

My doors all sit 100mm back on the concrete. This also makes them level with the concrete in the walls. The Thermohouse ICF blocks have a ‘check reveal’ which dictates where the doors and windows go, unless you want to cut it away. With ICF the concrete is where the cavity would be on a traditional block construction. 
 

I appreciate this isn’t helpful to your situation. 

[zzPaulzz]

 It does make me think though. The slab is not built yet, so maybe I will ask the SE to spec a shelf in the slab to extend it further just under the door openings. Doesn’t have to be full depth - 450mm ring beam at this point - but enough to take the load of the door off the XPS. 

[zzPaulzz]

2 hours ago, Iceverge said:

Cut out some of the XPS to allow the door frame to be partially supported by the concrete 

Yes, that might work. Will explore with me SE. 

[bmj1]

Great to see you being on top of this. I get the impression that threshold thermal bridges are frequently an afterthought, with professional builders happily slapping down concrete and creating a bridge...

Edited April 15 by bmj1

[Russdl]

We used GRP angle attached to/cast into the slab for all our exterior doors.

 

On our sliders I put 7 x 150mm M12 bolts through the GRP, threads extending into were the slab was going so that the bolts would be encapsulated in the slab when it was poured. It seems to have worked fine, no thermal bridge and enough strength to hold a big heavy slider. The slab was kept 25mm lower where the slider was going so that Compac Foam could be used under the sliding door threshold to insulate it from the slab. The front and back doors were much easier with their narrower thresholds.

 

Sliders

 

 

 

 

 

 

 

Front and back doors were simpler.

 

 

 

 

 

Edited April 15 by Russdl

[zzPaulzz]

That’s excellent detail, thank you!

[Iceverge]

Difference application but I bought some covered GRP grating for the thresholds of our house from eBay. 

 

Simply bridged the wide cavity block wall with it and sat the doors on top. The EPS blown beads filled the holes from underneath and thermally it was quite satisfactory. In computational reasoning at least. 

 

Stuff like this. 

 

 

[Nickfromwales]

Cut back the XPS and set Compacfoam in. I did this with a 4.9m slider, and set the Compacfoam in with flexible tile adhesive so I could tap it gently to level and set the required depth with great accuracy.

This isn’t about point loading, so doesn’t need such drastic work-arounds tbh.