Front door under threshold ideas

[Olf]

Yesterday I performed 'intrusive survey' of the existing floor and as it appeared to be easy to take up, with no floor height buildup due to extra insulation, replacement of the front door can go ahead.

Under the existing floor panels cracked bitumen showed, and when removed it became obvious why it cracked - it was on a layer of compacted stone/sand mix!

 

I removed as deep as could fit my hand through the gap and so here is a cross section of the situation:

 

 

Here is a view from the outside:

 

What puzzles me is that there seems to be a gap in the outer skin of the wall, the door frame sits on the step/slab in front, and that is poured over this compacted stone/sand mix that I could remove by hand. As the plan is to finish the renovation with EWI the step/slab would have to go anyway.

My idea is to remove the slab now, as it will make the access to dig up the rubble easier, and then fill the whole gap between the outer face and the inner skin with something like Compacfoam.

Later on the EWI (under DPC part) will go along that section.

 

My questions:

- is XPS viable alternative to Compacfoam in this case? It's like 1/6th of the price... Or something else?

- I'm assuming that under the compacted rubble I'll find bare ground - do I need to make any foundation for the foam?

 

Edited October 25, 2020 by Olf
Typos

[willbish]

9 hours ago, Olf said:

is XPS viable alternative to Compacfoam in this case? It's like 1/6th of the price... Or something else?

 

Compacfoam is the material of choice, but you may find something like GG700 is suitable (700kPa compressive strength). I used a combination of GG700 with a layer of Purenit over the top. SImply because I had enough Purenit leftover and the GG700 was significantly cheaper than compacfoam.

 

 

 

 

[Olf]

Thanks for mentioning Purenit, interesting material, though search does not find any place to buy it in the UK.

 

XPS might be cheaper, but it looks like no supplier will sell single board, manufacturer packs only, so not rosy here neither

 

My plan at the moment is to use Marmox Thermoblock, in their brochure it even states use under the threshold :

 

If my calculations are right, its declared compressive strength of 9N/mm2 equals to 9000 kPa, so beats XPS by far.

 

I'll pour some concrete to provide a bed for the Thermoblock, that will save me on trying to level the existing compacted layer.

 

[willbish]

I bought the Purenit from Construction Fixing Systems, was used for thermally separating cold steel from warm walls.

 

If you're near Bristol I have a few boards of GG700 lying around getting dusty

 

 

[Russell griffiths]

I had to buy a whole pack of XPS 500 it was only £75 and did one 5m patio door and two single doors.