MBC Frame - Windows - When to order ?

[bob the builder 2]

Hi All

 

We are heading down the MBC route and trying to decide when to order the windows.

 

Options seems to be;

 

1) Order off the MBC drawings

 

2) Wait until frame erected and order off the actual measured openings

 

The issue is lead times are around 5 months and we don't want the frame standing in the rain !

 

Any thoughts from the forum would be greatly appreciated.

 

 

 

[Thorfun]

friends had an MBC house and ordered their Rationel windows through MBC so it was all coordinated by MBC. is that not an option?

 

Also, you can always just board over (or cheaper these days maybe use DPM?) the window openings while you wait for the windows/doors to be delivered. 

 

we ordered our windows off the TF drawings and I think it is very common as the TF is normally very precise. plus 3 - 6 months wait is a killer if waiting until the TF is up! oh, and in our on-going experience the TF will be delayed. in fact, everything is always delayed we're finding. 

[craig]

Order of drawings, you shouldn’t wait until kit erected.

 

MBC should be ready within 10 days, windows should be going in then.

[SuperJohnG]

I ordered off drawings. All fine with no hassles, I just ensured the kit erectors had the correct structural openings once they completed. 

[bob the builder 2]

Many thanks for the confirmation - we will go for order off the drawings.

 

Any views on best window supplier for MBC frame - so far we have quotes from Internorm, Norrsken and Klober - all reassuringly expensive !

[Bramco]

You need them in as soon as possible after the TF erection is completed. Any delay can delay your airtightness test because the build needs to be wind and watertight before that.

 

We ordered from the plans - although having said that, they were the plans from the architect.

 

MBC designed the frame based on the structural openings in the architect's plans and these were what we signed off on.  They are then contractually obliged to build to the signed off spec.  If they don't, they have to fix it.

 

What this means is that you have to juggle the lead times of the windows people with the information you are getting from MBC about their start date on site and likely completion date. For us the windows had 10 week lead time, so they were ordered as soon as we had the dates from MBC.  Unfortunately like some others on here, we received an email from MBC about 10 days before the build start date that unfortunately they had had an issue with wood deliveries and they couldn't start until 4 weeks after the original date.

 

That's when the fun started. The rooflight  company wanted a stupid amount of money for storing the rooflights after the agreed delivery date, so we could only delay them by a week. The plan was that MBC would start on the garage and it would be up and completed by the end of the 1st week of the build. Unfortunately the steels didn't arrive, so there was nowhere to store the rooflights safely - we have found a safe spot now. The garage is likely to be the last thing completed...

 

With the windows, it depends on the supplier and whether they are doing the install. If they are doing the install as well - which is our case - then if there is no slack in their overall installation program, then you may find you are at the back of the queue again with a long delay. We were fortunate in that they could delay us by a month. 

 

MBC should finish the build this Friday (yee haaaa) and the windows will be delivered and installed on Monday week, so 10 days after MBC finish.

 

To give you some reassurance, I went over all the structural openings with the architect last weekend checking the measurements. They are all within a few mm of the spec and don't forget that the window manufacturers all allow for some tolerance of up to 10mm, these things aren't a friction fit.

 

Simon

Edited October 26, 2021 by Bramco

[bob the builder 2]

Thanks Simon

 

Just a follow on question - who did you go for on windows and rooflights ?

 

Also is your cladding / roof going on after the window install (just trying to clarify the sequence in my plan)

 

Many Thanks 

[Thorfun]

2 hours ago, bob the builder 2 said:

Also is your cladding / roof going on after the window install (just trying to clarify the sequence in my plan)

Our window company said to slate the roof first to ensure it’s fully loaded before installing windows. So that’s what we’re doing. Roofer starts in 2 weeks!

[Nickfromwales]

1 hour ago, Thorfun said:

Our window company said to slate the roof first to ensure it’s fully loaded before installing windows. So that’s what we’re doing. Roofer starts in 2 weeks!

On my current clients build there were some delays, so we've pushed ahead getting the windows in before the full weight loading can commence. I've strategized this by asking that the fixings for the heads of the windows be left so that we can tighten / loosen these fixings retrospectively after 30 or so days after final loads have been applied. That will be sufficient time for the TF to 'relax' and the weight above to transfer down onto the ground floor window heads ( if any does at all i'll be surprised tbh ) where we can then adjust accordingly.

[SuperJohnG]

I just installed Zyle Fenster 3g timber framed Aluclad supplied by Ecowin who is @craig on here. 

 

Plenty happy with the quality. I have black internally and externally. I had most of the slates on when wi down went in but if I didn't I wouldn't have been bothered. Plenty clearance at 10mm all round. 

 

Thats 4.6m wide and bottom 2.4m slider high

 

 

[Bramco]

12 hours ago, bob the builder 2 said:

Just a follow on question - who did you go for on windows and rooflights ?

 

Express in Leeds and Roofmaker in Leicester. Lots of reasons for selecting them rather than any other suppliers.  For example we hate the bump at the top of Velux rooflights.....

 

12 hours ago, bob the builder 2 said:

Also is your cladding / roof going on after the window install (just trying to clarify the sequence in my plan)

 

Our build will be roofed and clad in black corrugated metal - so not sure that weight is an issue for us. Also because our sliders are quite wide, MBC have designed steels above all of the openings and we have a guaranteed 2mm deflection on these openings.

 

8 hours ago, Nickfromwales said:

I've strategized this by asking that the fixings for the heads of the windows be left so that we can tighten / loosen these fixings retrospectively after 30 or so days after final loads have been applied.

 

Sounds like a good plan, I'll talk to the window installers when they start to see if we need to do something similar.

 

Simon

[laurenco]

On 27/10/2021 at 07:47, Bramco said:

Also because our sliders are quite wide, MBC have designed steels above all of the openings and we have a guaranteed 2mm deflection on these openings

 

Hi Simon, 

 

Can I ask where it says about MBC guaranteeing a 2mm deflection on the openings and how long this is guaranteed for? MBC did ours. 2019. (Very happy overall). But we're struggling to open the corner bi-folds and the contractor who came out has found the corner has dropped 10mm. 

 

Thanks

Lauren

[Bramco]

@laurenco

 

Hi Lauren,  the 2mm deflection is I think more about the centre of the structural opening and was a stipulation from Express doors for the sliding doors iirc.

 

A sag on one side would surely indicate that the side of the opening didn't have enough support? In our case, the steels sit on top of some chunky side supports.  If anything is still visible, I'll take a photo tomorrow.   No photo tomorrow, means nothing visible.

 

Your design looks much more difficult than ours. Our doors are all sliding doors within a wall, so nothing jutting out.

 

Simon

[Bramco]

@laurenco

 

Hi Lauren, no photos I'm afraid.

 

However it did strike me that you should be able to see the detail of the frame from the Site Pack.  The Site Pack contains all the details about the structure.  If you didn't get this from MBC, you should still be able to get hold of a copy.

 

Below is a snip of one of the structural openings. You can see the build up of 5 studs on each side of the structural opening to take the steel which is there to ensure the 2mm deflection at the centre of the opening.  In addition, the windows suppliers normally have a 10mm gap to allow them to actually get the windows in place, so actually there's plenty of tolerance - at least in our case.

 

Simon

 

[Nickfromwales]

On 24/05/2022 at 15:22, laurenco said:

the contractor who came out has found the corner has dropped 10mm. 

If the frame had dropped 10mm you'd have cracks the size of the San Andreas fault showing inside and out.

That looks like poor installation of the door frame, eg lacking support in the bottom corner of the frame where all the loads sit.

Have you had a spirit level on the door, door frame and threshold, both horizontally and vertically, to see which thing has actually gone awry? 

[laurenco]

3 hours ago, Bramco said:

@laurenco

 

Hi Lauren, no photos I'm afraid.

 

However it did strike me that you should be able to see the detail of the frame from the Site Pack.  The Site Pack contains all the details about the structure.  If you didn't get this from MBC, you should still be able to get hold of a copy.

 

Below is a snip of one of the structural openings. You can see the build up of 5 studs on each side of the structural opening to take the steel which is there to ensure the 2mm deflection at the centre of the opening.  In addition, the windows suppliers normally have a 10mm gap to allow them to actually get the windows in place, so actually there's plenty of tolerance - at least in our case.

 

Simon

 

Thank you, this is really interesting. I'm going to look at our pack

[laurenco]

2 hours ago, Nickfromwales said:

If the frame had dropped 10mm you'd have cracks the size of the San Andreas fault showing inside and out.

That looks like poor installation of the door frame, eg lacking support in the bottom corner of the frame where all the loads sit.

Have you had a spirit level on the door, door frame and threshold, both horizontally and vertically, to see which thing has actually gone awry? 

Good point! I'm going to get a spirit level on it all now...

[Nickfromwales]

1 hour ago, laurenco said:

Good point! I'm going to get a spirit level on it all now...

That will tell you immediately what has done what  

[craig]

Classic case of deflection here.

 

Not enough tolerance has been allowed been the door and the steel. Steel has deflected, most likely PU foam which turns solid has been used for installation/insultation. The steel has deflected, pushing down on the PU foam which can only push down on the frame of the corner opening bi fold which will not be a load bearing item. I can only think of two solutions. However, before this, take a level (laser preferably) and check. Speak to the bi fold supplier and find out what the measurement from the bottom track to the top track should be and measure it - you should be able to check this at each hinge side (wall side) of the bi fold.

 

It will all lead to a weight bearing issue from the deflection from above in the corner - that is what I highly suspect has occurred.

 

Solution 1: Open up above the bi fold, scoop out all the PU foam (that's what I presume has been used) and replace it with compriband only which is compressible. So when deflection occurs, it deflects into something that compresses so it doesn't push the top track of the bi fold down. 

 

Solution 2: Acro prop, push the roof back up (only slightly, you're only looking to get approx. 5mm). Look in the top tracks of the corner of the bi fold for a couple of locations you can pop 2 long screws in either side. Acro propping this up allows the screws to fix the item in place. Rather than trying to put the screws in an pulling the track up (which won't work). If you don't have an acro prop a car jack and a 2x2 and an another bit of timber to put between the ceiling and the 2x2 to try and prevent any damage to the ceiling.

 

In my honest opinion and looking at the pictures, this is the only remedies I can think off.

Edited May 27, 2022 by craig

[Gus Potter]

On 24/05/2022 at 15:22, laurenco said:

Can I ask where it says about MBC guaranteeing a 2mm deflection on the openings and how long this is guaranteed for? MBC did ours. 2019. (Very happy overall). But we're struggling to open the corner bi-folds and the contractor who came out has found the corner has dropped 10mm. 

Pity your bifolds are sticky.

 

Ok a bit of maths first!.. and a bit of a story.. grim at first but good news at the end! @laurenco

 

Say each of your bifold panels are conservatively 800mm wide, you have 3 panels. Thus from the top outside corner of the doors back to the roughcast on the main house wall you have a distance of 2400mm. Above the bifolds you have a section of rendered construction, above that the frameless glass, more forgiving often in terms of movement than the bifolds. Now the panel above the bifolds will be fairly stiff on the inside and to some extent flexible between the inner and outer rendered layer. The load from the balcony will likely be on the inside and you'll probably have some flexible ties so any movement within the panel structure above the doors won't immediatly manifest as cracks in the render. But assume (conservatively) the panel above the doors maybe acts as one unit and rotates about the point where the bottom of the rendered panel meets the main house wall at the level of the top of the doors.

 

Now assuming the panel above the doors acts as a unit then if the outside corner of the panel above the top corner of the doors drops by 10mm that means that the panel rotates downwards by tan (angle) = 10 /2400 = 0.24 degrees. If the panel above the doors is 900 mm high then at the point where the bottom of the balcony glass meets the main house wall you could expect a crack to be at the top end of tan( 0.24 deg) * 900 = about 3.8mm.. not a lot actually and hard to see. That may be why you don't see massive cracks at the moment. Even then you would be hard pushed to distinguish this between movement crack and a shrinkage crack.

 

Going back to your design and looking at it conceptually there are a few ways of designing this as an SE. You have the balcony above so a bit of load there, doors that are sensitive to movement, a timber frame that shrinks and swells season to season and also dependant on how warm / cool you like your house.. it's a "living" thing that reacts to moisture changes. Timber frame.. it's going to move about quite a bit! a lot more than 2.0mm on standard stuff, any cantilever arrangement is going to move a lot more than 2.0mm.

 

A first glance to design something SE wise like you have I would ask what your budget is. If you are very tight for cash but still want that type of bifold arrangement I would look at making the outside corner of the bifold as a hidden structural post / column. If you want, look up a window bay pole on the internet that will give you the jist of it. The thing here is that you remove the cantilever effect, reduce significantly movement, make significant savings not just on the balcony, beams but also on how you connect the produding balcony back to the timber frame. MBC may have made this "baypole" assumption so check. The design philosophy is often lost in the wash and that is how these things happen.

 

Alternatively you can go for everything cantilevered out from the main house wall, using the first floor as a means of supporting the cantilever. You will get a lot of movement here though. If you use steel and ordinary bolts then the bolts go in holes of 2.0mm greater diameter than the bolt size.. the bolts initially can move about before they take up their final position.

 

To sum this up. Your starting point here is to go back to the structural design and see how it was intended to work, what caveats the SE specified, the design deflection limits. If you want post more info it would be of interest.

 

If the SE has gone for the "bay pole concept" .. a column at the outside corner, could just be a heavy aluminium corner frame?  then you need to check that the bifold supplier has been made aware of this and implemented that SE requirement.. if not you have a major safety issue you need to address.

 

If you check this structural stuff out first and make sure there is not a fundamental structural problem and all is ok then I would, as a next step, get a hold of a local window / door installer that knows their stuff to give you the right advice. It may be that all you need to do is take the beads off, square the frames up by repacking the glass with the plastic spacers... one days work and that will be you for a good few years until the moving parts wear a bit, then get the same guru back! Sometimes things jamb as the spacers between the glass and frame at the top of the door come loose and slip down so the frames sag and get sticky.

 

@craig good point about scooping out the foam and how it hardens up. Now sure about jacking stuff as a first choice personally until you really get to the root of the problem. Lifting things locally could move other structural stuff off their friction bearing that we rely upon and that could lead to structural instability.. you can lift several tonnes with an accrow one you set you mind to it.. great fun but there are concequences. That said, once you understand what the problem is then controlled jacking and packing is a good potential solution.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[craig]

On 27/05/2022 at 23:31, Gus Potter said:

Now sure about jacking stuff as a first choice personally until you really get to the root of the problem.

 

Which in my experience, no one wants to take responsibility for and or advises that the issue is the window/door suppliers problem for not allowing the relevant tolerance in the first place. Which to be fair is a valid point, however, obtaining the deflection in the first instance can be like getting a needle from a haystack. Usually the simplest solution is to just jack things up a touch (just enough) to get the clearance for smooth operation to occur and then fixed the unit again in that position.

It invariably falls onto the window/door supplier and isn't always there fault.

[Gus Potter]

On 28/05/2022 at 23:41, craig said:

 

Which in my experience, no one wants to take responsibility for and or advises that the issue is the window/door suppliers problem for not allowing the relevant tolerance in the first place. Which to be fair is a valid point, however, obtaining the deflection in the first instance can be like getting a needle from a haystack. Usually the simplest solution is to just jack things up a touch (just enough) to get the clearance for smooth operation to occur and then fixed the unit again in that position.

It invariably falls onto the window/door supplier and isn't always there fault.

Hi Craig.

 

Agree with what you say, especially with bifolds, big sliding doors. It only takes a bit of poor joinery work on the kit and things will settle, timbers that have got too wet on site and suffer from excess shrinkage, move off the square, bit of settlement in a found and if you have a combination of these small movements in aggregate you often get enough to make things start to stick.

 

Unfortunately it's often the window / door installer that get the blame first.. last person on the job is often the first to get it in the neck.. money can be unjustifiably withheld.

 

I would still though be careful about jacking as later if you say get a fall of snow, or say full load on a balcony above and things dry out more, masonry further shrinks then it could all just drop back down again and loosen things off even more.