Door threshold in MBC timber frame

[divorcingjack]

Hi all, 

 

Does anyone have a thermally efficient, close to level door threshold detail that will work with an MBC insulated slab and timber frame? We have one door in an area which is brick clad, one in a timber clad section and a very big lift and slide internorm door as well. We also have 3 tilt and slide windows as well, and MBC have just asked me what threshold we'd like. I'm concerned about supporting the weight of the lift and slide, as I presume any sill/threshold will act as a thermal bridge?

 

Is there an approved detail that will work? 

 

Thanks for any advice, 

dj 

[Alex C]

I have just been through this and have flush internorm lift and slide as well as front and back door. Internorm will want you to support as much of the aluminium extrusion at the base as possible (well actually all of it). I have attached my sections that everyone eventually seemed pretty happy with. The issue is actually managing to shutter the slab accurately on site to get a level step down detail. My installers from Ecohause were not only expensive, but also terrible, but after several attempts managed what seems to be ok. When you say approved detail, who do you want it approved by? No-one is going to sign on a dotted line with anything other than full support to the slider or door base, but obviously that will be a massive thermal bridge.

 

 

window gf06 section.pdf

sliding door section.pdf

[Barney12]

Interesting thread as I will face the same issue as I also intend to use MBC and Internorm Lift and Slide.

 

what interests me is it seems to suggest that what has been written in the two posts above seems to imply that MBC have said "what do you want" where their sales pitch is very much "we work with your chosen window supplier"?

 

Surely if they're building as many houses as they claim and as they also claim regularly work with Internorm they must have provided this detail before?

 

 

[divorcingjack]

Thanks for the replies both. Alex - thank you so much for those details, I will pass them along to our architect for him to have a look at. By approved detail, I just meant one that is reasonably robust and thermally efficient, not "officially" approved. I unfortunately don't know enough to assess how good a threshold detail is, so was looking for a "pretty good" example to show to MBC and my architect as a shortcut for my preferred option. This forum is so useful as everyone understands the issues with airtightness and thermal bridging, so I tend to use it as something of a "hive mind". 

 

Barney - perhaps my wording put across an incorrect impression. MBC have been nothing but helpful, but I had an email the other day asking if I'd like a recessed threshold or not, and I'm doing this more for my own curiosity. I haven't received the drawings from MBC yet, so I'm sure their detail will be great. They also told me that they have worked with Internorm before, but there is an added complexity with our case that our dealer has gone under, so we don't have a local contact to chase for approved internorm details etc. 

 

I am concerned about providing sufficient support for the big sliders though and what sill to use, as I was just told that Interterm don't provide sills?! Mind you, I wouldn't trust our original salesman as far as I could spit, so who knows what incorrect info I have been given. 

 

 

 

 

[IanR]

While I've not got lift'n'slides, I'm due to have an Internorm package that includes low threshold entrance doors as well as a 4.2m high window group that sits entirely over the EPS upstand and are set down 50mm from FFL into the slab.

 

Ecohaus were happy with the detail we developed that has a 9.5mm thick GRP profile sitting on top of the EPS with its edge set into the slab. I do have a block plinth running around the outside of the EPS upstand, and the other edge of the GRP profile is sitting on this plinth wall.

 

Mine is not a MBC/VH raft, but is an AFT Engineered raft.

 

52 minutes ago, Alex C said:

 Ecohause were not only expensive, but also terrible,

 

That's ominous, they're arriving at mine in two weeks.

 

@Alex C can I ask what blinds you are going with. I'm looking at Hunter Douglas.

[divorcingjack]

Thanks Ian, is your build timber frame as well? Where did you source the GRP profile? 

 

I'd be interested in the blinds too - our window is about the same height as yours and directly south facing. Although we have an overhanging canopy, I definitely want to have the option for tracked blinds too, but getting the width and drop for the group is neither easy nor cheap

[IanR]

I'll remind myself of the exact details of the profile and PM you. It's not specifically made for this purpose, but is cut down from a "U" profile.

 

My 4.2m high window is 5m wide, so I can't cover this in a single blind. The height can be done, and the width can be done, but not at the same time (that I've been able to find). I've got a horizontal split in this window and only actually plan to cover the top half with a blind, down to the split. 

 

 

[divorcingjack]

Ours is 5m wide too, it's not easy  

 

Thinking of rigging up some kind of outdoor arrangement with sailcloth!

[TerryE]

OK, right or wrong, here is what we did.  I cut a 50mm channel in the EPS300 perimeter at our 4 Internorm door openings (2 conventional doors and 2 tilt and open double french doors)  I also attached an extra 45×50×<door width> shuttering the outside to extend this as a tongue out into the airgap. This was rebared and poured and levelled as part of the MBC base pour.  We also used OSB3 (though in retrospect I would recommend marine ply to others) boxing on top and sides of the door openings to bring the line of the doors (and windows) 45mm out in front of the frame and close the airgap.  We allowed for this framing in our MBC opening calcs as you need to add this plus10-15mm filling gap to the the frame sizes to get the MBC openings right.  The frames sit behind the stone skin.

 

The bulk of the weight of the doors and frame is carried by steel straps attached to the framing box, but the foam filler and silicon also carry the load into the boxing frame.  The Internorm doorframes sit on a 30mm high spacer (that ecoHaus provide as standard) and this sits on the concrete tongue.  We have a stone skin that is ~150mm and I've used Perinsul load bearing blocks butted up to the tongue, with the top level with the slab.  The actual cill is slate bedded on top of the Perinsul blocks.  OK in theory the slate might touch the concrete tongue on the diagonal, but the area of the bridge is tiny, so I don't think that this will be a material issue. 

Edited August 16, 2016 by TerryE

[worldwidewebs]

1 hour ago, divorcingjack said:

there is an added complexity with our case that our dealer has gone under, so we don't have a local contact to chase for approved internorm details etc. 

Who was your dealer? I'm just about to put a deposit on some Internorm windows!

[worldwidewebs]

2 hours ago, Barney12 said:

Interesting thread as I will face the same issue as I also intend to use MBC and Internorm Lift and Slide.

 

what interests me is it seems to suggest that what has been written in the two posts above seems to imply that MBC have said "what do you want" where their sales pitch is very much "we work with your chosen window supplier"?

 

Surely if they're building as many houses as they claim and as they also claim regularly work with Internorm they must have provided this detail before?

 

I'm in the same boat too. I did ask the question in the last week or so as Internorm suggested around a 45mm recess and I did get an answer, but I think I need to re-ask to ensure there aren't any expensive mistakes. I'm sure it's pretty straight forward really  

[Alex C]

_{The only information Ecohause internorm would give me was to say they needed a 30mm recess in the slab, and when pushed for weeks finally said ok to my section detail. MBC did not give any information on how to create this detail, although I think this level of information is very dependent on the individual who is doing the design work. I had to do all of the work myself for the window and slider support and produced my own drawings. My blinds are from Internorm, although Ecohause Internorm knew less about their own product than I did. The installers had never seen them before.}

[Stones]

1 hour ago, TerryE said:

OK, right or wrong, here is what we did.  I cut a 50mm channel in the EPS300 perimeter at our 4 Internorm door openings (2 conventional doors and 2 tilt and open double french doors)  I also attached an extra 45×50×<door width> shuttering the outside to extend this as a tongue out into the airgap. This was rebared and poured and levelled as part of the MBC base pour.  We also used OSB3 (though in retrospect I would recommend marine ply to others) boxing on top and sides of the door openings to bring the line of the doors (and windows) 45mm out in front of the frame and close the airgap.  We allowed for this framing in our MBC opening calcs as you need to add this plus10-15mm filling gap to the the frame sizes to get the MBC openings right.  The frames sit behind the stone skin.

 

The bulk of the weight of the doors and frame is carried by steel straps attached to the framing box, but the foam filler and silicon also carry the load into the boxing frame.  The Internorm doorframes sit on a 30mm high spacer (that ecoHaus provide as standard) and this sits on the concrete tongue.  We have a stone skin that is ~150mm and I've used Perinsul load bearing blocks butted up to the tongue, with the top level with the slab.  The actual cill is slate bedded on top of the Perinsul blocks.  OK in theory the slate might touch the concrete tongue on the diagonal, but the area of the bridge is tiny, so I don't think that this will be a material issue. 

 

Our builder / ICF construction uses a similar strategy, extending the slab into the door way so that the door threshold has something solid to sit on.  Not the best of pictures as i wasn't concentrating on this detail, but you can see how the slab extends through the ICF foundation blockwork for the door openings. 

 

 

You can just see in the last picture the PU upstand insulation behind the timber former so the finished opening is flush with the outer face of the ICF block   External insulation still to be fitted onto the outer face of the ICF block.

[worldwidewebs]

Why am I now worrying...?

[Alex C]

I should also add that it took Ecohause Internorm 4 weeks to produce their sign off drawings and then the contractual maximum of 14 weeks to manufacture the windows. You might well of guessed that I am not a happy customer. I had to get their first set of installers to leave my site as they were completely incompetent and damaged nearly every window. All windows and doors had to be refitted. I am still awaiting refitting of items and re sealing around glass as none of it was completed to a satisfactory standard.

[IanR]

51 minutes ago, Alex C said:

I should also add that it took Ecohause Internorm 4 weeks to produce their sign off drawings and then the contractual maximum of 14 weeks to manufacture the windows. 

 

This has been my experience also, although it took 6 weeks to get the contract correct and approved. Install is 4 weeks later than I had planned.

 

I assume they are suffering from the success of the Autumn Internorm promotions.

[divorcingjack]

The comments about the fitting and service are so disappointing and has been my experience with a lot of companies and professionals so far, although a few notable exceptions - my architect and MBC being two. I'm by no means an expert, but there's been lack of communication, mistake after mistake, lack of listening to what I actually asked for, patronising, blatant lies etc etc. You pay a fortune, you expect people to be professional and do a good job! Cheap windows I could understand paying your money and taking your chance, but Internorm are definitely NOT cheap! I wonder if the parent company are aware of the antics of some of their dealers. 

 

Alex, that sounds a nightmare! I hope you managed to get it sorted out in the end, but not without cost,  I imagine. 

 

Terry, thanks for the info, the pictures are so helpful

 

dj 

[TerryE]

In a self build you will rely on your major subs.  One of the major reasons that initially attracted me to MBC was that they offered both the slab and the timber frame and this de-risked a major interface for me. 

 

Even so, the windows and doors are a major risk because these work at the interface between 3 / 4 subs: the window/door supplier,  the slab, the timber frame and the exterior cladding.  None of these contractors is prime, so this interfacing risk is on you -- or your architect if he or she is good enough.  There's no free lunch.  Appoint any one contractor prime (assuming that the accept it) then they'll charge ~5% management fee to cover the risk and effort of interfacing to the others.  Your architect will charge ~7% and their contribution / value-add is seen as controversial by many self-builders, myself included.

 

If you don't have a prime or overall overseer, then this role doesn't go away.  Individual contractors work within their contract scope of supply to deliver a good product and turn a decent profit for themselves.  It's not their fault to remedy if the customer specification is wrong.  Working out how the windows interface to the slab, frame and skin is down to you or your architect.   If your architect isn't totally on top of this, then you should really ask yourself what they are doing to justify their fee and also accept that you have to get your head around how this is going to work out in fine detail and in practice.

 

I would also add that Alex's nightmare isn't a nightmare; this timescale is pretty typical, and you should budget this in your planning. 

[divorcingjack]

10 hours ago, TerryE said:

 

I would also add that Alex's nightmare isn't a nightmare; this timescale is pretty typical, and you should budget this in your planning. 

 

I didn't mean the timescale, I meant the fact that the fitters damaged all his windows! Surely that's not standard

 

Our architect is very good and I have every faith in his details - but the lack of a prime contractor is why I'm on here, to try and educate myself as to how things should be. I was just pointing out that when you pay professionals, it's a shame that we feel the need to double-check their advice and look out for errors, you should be able to rely on them. That goes for everything in life though, buying a house, getting financial advice, buying a car etc. The amount of simply incorrect information I have come across in the financial arena is terrifying. 

 

dj

 

 

[worldwidewebs]

8 minutes ago, divorcingjack said:

when you pay professionals, it's a shame that we feel the need to double-check their advice and look out for errors, you should be able to rely on them.

 

All a professional is is someone that gets paid for doing 'a thing' - it has absolutely no bearing on whether they are good or not.

 

So far, pretty much everyone I've worked with has been great - but I've also pulled every one of them up on more than one thing that I'd consider pretty basic stuff that either they should have brought to my attention first, or that should have just been dealt with without my intervention. The only comfort in all this is that I know there is more of this to come so I just try and be as prepared as possible

[TerryE]

As old Ronald Reagan said: trust but verify

[divorcingjack]

I just wanted to thank you all for your input, I have now got a suggested detail from MBC  Can't say that I understand it 100%, but at least they've had some other info to look at!

 

[dogman]

Did anyone else who has an MBC slab get any different designs

 

After a long delay i had the first design back last week. Despite my initial instructions the threshold detail was a 75mm tongue to the edge of the slab which gave a horrendous cold bridge

 

I asked for a redesign and had this back on Friday

 

threshold.pdf

 

This is not their drawing but my representation due to limitations in my drawing software but dimensions are correct.

 

The doors are lift and slide and must be fully supported across the width of the frame.

 

This will give me a 100mm of the insulation. 

 

I intend to stick a further 50-100mm insulation strip on the outside before it is rendered

 

the door details are below

 

40 Ecoclad_patio_Threshold Layout.pdf

 

I can get upto a 240mm cill and my understanding is these are insulated and thermally broken.

 

Can anyone see any issues with this and has anyone had a better design from MBC

 

[Jeremy Harris]

Same as mine.  100mm of EPS outboard of the door threshold instead of the 200mm everywhere else, because of the rebate cut into the EPS upstand to support the door frame. 

 

Not a biggie in terms of being a thermal bridge, as all around the frame of the door is a hell of a lot worse!

[dogman]

Thanks @JSHarris My MBC designer has been off for a few days so hopefully will get it back tomorrow.