Windows & Doors into ICF openings....

[Mulberry View]

Just wrapping up the final stages of preparation for ordering our windows. Those of you that have done an ICF (particularly Nudura) build, did you install your windows directly into the Nudura openings with their EPS closers?

 

I have removed the EPS from the threshold of the openings for our 2 heavy sliding doors, they will be mounted onto the concrete, but how about the rest of the 'normal' windows and doors?

 

This is one of the larger openings, it's about 3.5m wide and the window will weight about 350kg.

 

[Nickfromwales]

I know of one where they followed ‘common procedure’ and every window leaked rainwater in through the sides / base of each opening (nothing to do with the units, purely down to lazy / uneducated installers). 

 

This was on a 7 figure project, expensive / reputable fenestration provider, and only showed after the first winter; this meant the render had been done, and was all a total loss.

 

Get digging as it’s not a walk in the park to get this right. 

[Mulberry View]

3 minutes ago, Nickfromwales said:

I know of one where they followed ‘common procedure’ and every window leaked rainwater in through the sides / base of each opening (nothing to do with the units, purely down to lazy / uneducated installers). 

 

This was on a 7 figure project, expensive / reputable fenestration provider, and only showed after the first winter; this meant the render had been done, and was all a total loss.

 

Get digging as it’s not a walk in the park to get this right. 

 

I've got a fairly comprehensive detailing approach, we have a bespoke Aluminium reveal trim going in.  I'm planning to coat the openings with Wykamol Technoseal Liquid DPM before the windows go in to help the airtight tapes to stick. They'll be sealed with FM330 and ME508 tape (or similar).

 

I just want to be sure of the load bearing ability of the EPS. ChatGPT seems to think it'll be OK, but I don't totally trust that.

[Nickfromwales]

One thing I’d recommend is putting a slight slope, from inside to out, in the bottom of the opening.

 

Tanking and sealing etc will arrest and collect water, which eventually finds its way forwards and out, but I’d prefer to get that happening naturally vs displacement. 

[Russell griffiths]

Straight onto the eps, we discussed this a while back, the windows are heavy, but divide the weight by the area and the downwards pressure is very minimal. 
 

 

[Mulberry View]

Just now, Russell griffiths said:

Straight onto the eps, we discussed this a while back, the windows are heavy, but divide the weight by the area and the downwards pressure is very minimal. 
 

 

 

Norrsken said they wanted Compacfoam CF400 for the above window, but I'm also mindful that they aren't the authority on load bearing capabilities of a system they don't know.

 

I have upgraded the standard door openings to Danopren TR50 (EPS300) in the thresholds and I will probably do the sill of the above window with that because I have it, but it would be nice if I can leave the rest as-is.

[Russell griffiths]

Just now, Mulberry View said:

 

Norrsken said they wanted Compacfoam CF400 for the above window, but I'm also mindful that they aren't the authority on load bearing capabilities of a system they don't know.

 

I have upgraded the standard door openings to Danopren TR50 (EPS300) in the thresholds and I will probably do the sill of the above window with that because I have it, but it would be nice if I can leave the rest as-is.

Look at kingspan green guard 500. I put that under our doors. 

[Russell griffiths]

5 minutes ago, Mulberry View said:

 

Norrsken said they wanted Compacfoam CF400 for the above window, but I'm also mindful that they aren't the authority on load bearing capabilities of a system they don't know.

 

I have upgraded the standard door openings to Danopren TR50 (EPS300) in the thresholds and I will probably do the sill of the above window with that because I have it, but it would be nice if I can leave the rest as-is.

Norrsken wanted 30mm clearance above my door for deflection of the rsj above the door, I told them it was icf construction so no rsj, they couldn’t understand how it held itself up. 
do your own research and make a decision, a few companies arse covering goes to silly levels. 

[Mulberry View]

2 minutes ago, Russell griffiths said:

Look at kingspan green guard 500. I put that under our doors. 

 

Yes, my ground floor slider is 4.2m wide, 2.5m high, its about 750kg. I've stripped the top closer away to the concrete, but the profile is deeper than the 150mm core. I've got to extend the load bearing face rearward and I'm planning to use something like GG700 for that, but it'll be a 200x200 section, so pretty hefty.

[Nickfromwales]

16 minutes ago, Mulberry View said:

 

Yes, my ground floor slider is 4.2m wide, 2.5m high, its about 750kg. I've stripped the top closer away to the concrete, but the profile is deeper than the 150mm core. I've got to extend the load bearing face rearward and I'm planning to use something like GG700 for that, but it'll be a 200x200 section, so pretty hefty.

Just supported with a full house install of Norrsken doors and windows.

 

We used Bosig Phonotherm under the front door and sliders, very easy to work with and strong as a Trebor Extra Strong mint.

 

Used liquid DPM under and over it, for belt and braces.

 

A few days before they were due to go in I spotted some typos in the structural openings schedule. Bloody good job I did too, as the door and slider were different than stated. Door slightly smaller, and sliders ~35mm taller ffs.

 

Pulled the head of the porch out and rebuilt it to suit, so even the big boys get it wrong. 

[Mulberry View]

8 hours ago, Nickfromwales said:

Just supported with a full house install of Norrsken doors and windows.

 

We used Bosig Phonotherm under the front door and sliders, very easy to work with and strong as a Trebor Extra Strong mint.

 

Used liquid DPM under and over it, for belt and braces.

 

A few days before they were due to go in I spotted some typos in the structural openings schedule. Bloody good job I did too, as the door and slider were different than stated. Door slightly smaller, and sliders ~35mm taller ffs.

 

Pulled the head of the porch out and rebuilt it to suit, so even the big boys get it wrong. 

 

Yes, I've seen Phonotherm, not sure if it can work for what I need though. I've essentially got to cut the inside 68mm EPS away and replace it with something more load bearing. I thought it would be really easy (shutter and pour a strong concrete mix or something), but SE threw me into a bit of a spin by not being keen on that way.

 

I have the same problem on the first floor, but there I have extended the load-bearing depth with a piece of 8x2 C24 installed onto the concrete core level with the threshold, but I cannot employ this same technique on the ground floor.

 

 

This is the best I can come up with for the Ground Floor, a 200x200 block of XPS700 installed up against the inside of the concrete core. (I have lowered the concrete now to make the door fully flush, though this isn't shown on this detail).

 

 

Apparently, it needs to be a deep as it is tall ideally, not sure why, hence the oversize of it. The overhang of the door is actually only about 30mm or so. This still seems tricky to install because the XPS700 and door will have to go in before the rest of the insulation and screed etc which would have pinned it into place.

 

I don't really want to put the DPM and PIR in for the floor until after the doors are fitted, but what to do where it laps under the door threshold?

 

 

[Mulberry View]

On 09/11/2025 at 11:31, Russell griffiths said:

Norrsken wanted 30mm clearance above my door for deflection of the rsj above the door, I told them it was icf construction so no rsj, they couldn’t understand how it held itself up. 
do your own research and make a decision, a few companies arse covering goes to silly levels. 

 

Which Norrsken window profile did you go for?

[Nick Laslett]

My windows are all sitting on the EPS cavity closer in the middle of the ICF block. 
 

The largest window is 2730mm x 1750mm.

 

They are aluminium frames, with 190mm cills. 27mm thick double glazed units, weighing approx 25kg / m2. 
 

Thermohouse EPS is slightly denser than Nudura at 24 kg/m³ vs 21 kg/m³. 
 

For reference Marmox XPS shower formers have a density of 36 kg/m³.

They have been in over 3 years and seem to be alright. 

 

Edited 18 hours ago by Nick Laslett

[Nickfromwales]

2 hours ago, Mulberry View said:

 

Yes, I've seen Phonotherm, not sure if it can work for what I need though. I've essentially got to cut the inside 68mm EPS away and replace it with something more load bearing. I thought it would be really easy (shutter and pour a strong concrete mix or something), but SE threw me into a bit of a spin by not being keen on that way.

 

I have the same problem on the first floor, but there I have extended the load-bearing depth with a piece of 8x2 C24 installed onto the concrete core level with the threshold, but I cannot employ this same technique on the ground floor.

 

 

This is the best I can come up with for the Ground Floor, a 200x200 block of XPS700 installed up against the inside of the concrete core. (I have lowered the concrete now to make the door fully flush, though this isn't shown on this detail).

 

 

Apparently, it needs to be a deep as it is tall ideally, not sure why, hence the oversize of it. The overhang of the door is actually only about 30mm or so. This still seems tricky to install because the XPS700 and door will have to go in before the rest of the insulation and screed etc which would have pinned it into place.

 

I don't really want to put the DPM and PIR in for the floor until after the doors are fitted, but what to do where it laps under the door threshold?

 

 

Your detail there seems way OTT to me! Is that what your SE told you to do for a window?!  

[Oz07]

Do you guys cover the outside of insulation with anything to stop rodents getting in below door thresholds?

[Mulberry View]

56 minutes ago, Nickfromwales said:

Your detail there seems way OTT to me! Is that what your SE told you to do for a window?!  

 

That's a Sunflex SF80 Triple-Glazed Slider. The one on the Ground Floor weighs around 750kg (4.2m long), the First Floor one is probably about 400kg.

 

The SF80 profile is 210mm, the concrete core is 150mm. The supplier would not approve installation where the frame was not fully supported. In all fairness, the timber add-on was pretty easy, it's yet to have a layer of insulation over it that will lap up the back of the frame.

[Mulberry View]

4 minutes ago, Oz07 said:

Do you guys cover the outside of insulation with anything to stop rodents getting in below door thresholds?

 

Mine has Permaguard Dimple membrane and a french drain around the perimeter. The door thresholds will have an EPDM layer over them too.

[Nickfromwales]

2 hours ago, Mulberry View said:

 

That's a Sunflex SF80 Triple-Glazed Slider. The one on the Ground Floor weighs around 750kg (4.2m long), the First Floor one is probably about 400kg.

 

The SF80 profile is 210mm, the concrete core is 150mm. The supplier would not approve installation where the frame was not fully supported. In all fairness, the timber add-on was pretty easy, it's yet to have a layer of insulation over it that will lap up the back of the frame.

Ground floor one is sat on your slab, so zero issue there?

 

Upstairs one can be sat on something like Compacfoam or Bosig, as the weight is at the centreline of the glass and frame, so around 100-150mm of ‘meat’ at the ICF core is already ample. Spread out over the core and the EPS means 400kg is lost across the surface area with complete ease.

 

The detail in your above section shows this half over structure and half over EPS block, so you should have the same detail for the window openings afaic. 
 

I’ve never done / seen timber bolted into the ICF core for a window before. 

[Mulberry View]

11 hours ago, Nickfromwales said:

Ground floor one is sat on your slab, so zero issue there?

 

Upstairs one can be sat on something like Compacfoam or Bosig, as the weight is at the centreline of the glass and frame, so around 100-150mm of ‘meat’ at the ICF core is already ample. Spread out over the core and the EPS means 400kg is lost across the surface area with complete ease.

 

The detail in your above section shows this half over structure and half over EPS block, so you should have the same detail for the window openings afaic. 
 

I’ve never done / seen timber bolted into the ICF core for a window before. 

 

To clarify, the photo is of the first-floor sliding door position. The architectural detail is of the ground floor position, where the core of the concrete is abundantly strong. As you can see from the detail, the majority of the triple-glazed sliding leaf overhangs the concrete and onto what would have been the EPS inner skin of the Nudura (which apparently does not have the compressive strength for the weight it would be subjected to). ID Systems (the Sunflex installer) wants the door to be fully supported and do not consider the EPS to be sufficient. The Architect suggested a 15mm layer of Bosig Phonotherm laid flat over the concrete for the door to bear onto. This would still overlap onto the "insufficient" EPS, but significantly would have required me to take the concrete (C35) down by ANOTHER 15mm (I had already taken it down by about 20mm to allow for a fully flush installation, which took me several days and I was VERY pleased with the finish).

 

The ground floor is Beam & Block and so it is a case of either widening the load-bearing width of the concrete core or transferring the load down to the B&B with a media that has sufficient compressive strength. It could theoretically have been a length of RSA resin bolted to the inside of the concrete core to provide a platform on which the rear portion of the door could sit, but that's not the most thermally efficient solution and I'm not sure it's smart to have a piece of steel in the subfloor like this.

 

This is the ground floor position. The inner Nudura EPS skin is still in place and it is that I, apparently, need to remove and replace in order for ID Systems to be happy to install the door...

 

 

 

Obviously we have a layer of PIR to go into the floor yet and that detail essentially replaces an outer band of the PIR with a lump or XPS700 that the door will sit partly on. It's just a little confusing to think of how to implement it!

 

In the first floor position, we did not have the benefit of anything structural beneath the inner Nudura EPS insulation, which goes all the way down to the ground. Steel RSA was proposed here again, but timber was also an option, which was far easier to implement. My SE knows that I prefer overkill and might be pandering to that.

 

This is the first-floor detail, it leads out onto a balcony.

 

[Russell griffiths]

20 hours ago, Mulberry View said:

 

Which Norrsken window profile did you go for?

No idea it was 4 years ago. 

[Russell griffiths]

17 hours ago, Oz07 said:

Do you guys cover the outside of insulation with anything to stop rodents getting in below door thresholds?

I’ve rendered all mine below dpc.