Bifold structural opening issue

[messtin]

Hello everyone,

We have just had some structural alterations made to our property to create a large open plan kitchen diner area. As part of the works, an opening has been made in the exterior wall of an existing lean too single story extension for a set of 3.1m wide bifold doors that are bottom running.

The construction of this extension is a cavity wall with a wooden frame internal structure and blockwork outer, so we have the existing sistered 2x6s, soon to be reinforced with steel angle acting as the load bearing lintel on the inner wall at the opening.

However, due to a low level window on the second floor of the property and the resultant roof pitch, the outer wall does not have any block courses above the openings for the windows and doors. Where the existing windows are, there are timber frame cavity lintels in place, but there is nothing holding them down on the outer course, except the soffit boards that rest on them and the metal plates that are hammered in on the upstands to prevent twisting.

The existing windows were not fixed to these mechanically, but were tacked to them using expanding foam adhesive. So my question is, whilst bottom running, the bifold doors need something for the top of the frame to be fixed into if we are to install them in the outer wall as planned, but I am unsure how to provide something secure for the fitters to screw to as the existing timber frame cavity lintels are not secured in place.

My initial thought was to remove the existing cavity lintel and laminate some timbers together, attaching them onto the internal 6x4 timber lintel so that they bridge the gap to the outer wall, however with the angle of the rafters, this would be quite fiddly and would require chamfered cuts to the bridging timbers.

Any suggestions would be greatly appreciated

Thanks

 

[RonnyRaygun]

I'm confused by the question (and I'm guessing from the lack of replies, everyone else is too).

I'm not sure why the existing windows are relevant to the securing of the bifold to the lintel?

The steel angle above the external leaf doesn't look like the best detail - I'm not sure how it's held in place laterally. It's obviously not carrying any load. There are some thin timber pieces coming off the rafters - how are they connected to the lintel, if at all?

If you are looking to fix the frame of the bifold to the lintel to restrain the head of the door you need the lintel itself to be held in place laterally, else it won't offer any benefit.

I think I agree that you need to secure the lintel back to the timber lintel behind. How about simply some blocks of wood at 600mm centres cut to the correct width between the timber lintel and the external angle? Then simple drill a couple of holes through the steel lintel and use long screws to fix into the timber lintel behind? Would that work?

 

[messtin]

forgot to quote...

 

[messtin]

I'm confused by the question (and I'm guessing from the lack of replies, everyone else is too).

I'm not sure why the existing windows are relevant to the securing of the bifold to the lintel?

The steel angle above the external leaf doesn't look like the best detail - I'm not sure how it's held in place laterally. It's obviously not carrying any load. There are some thin timber pieces coming off the rafters - how are they connected to the lintel, if at all?

If you are looking to fix the frame of the bifold to the lintel to restrain the head of the door you need the lintel itself to be held in place laterally, else it won't offer any benefit.

I think I agree that you need to secure the lintel back to the timber lintel behind. How about simply some blocks of wood at 600mm centres cut to the correct width between the timber lintel and the external angle? Then simple drill a couple of holes through the steel lintel and use long screws to fix into the timber lintel behind? Would that work?

Hi Ronny, thanks for the reply.

Yes, your right, I was struggling to describe the issue properly to be honest!

I probably should have phrased my question differently as what was there previously is irrelevant to the current problem.

I also didn't make it clear that the steel angles in the photos were actually what was above the old windows and cannot be used above the new opening for the doors as they do not have sufficient span, plus they are not securely fixed to anything. The builder didn't think that the doors would need any top fixings, so left them in place to give something for the frame to be sealed up against. It was only when the bifold supplier came to survey the opening, they said they would need something above the doors to fix to. The builder is unable to return to site before the fitting date, so I am having to sort this myself.

The small bits of timber were there in an attempt to hold down the steel and soffit boards.

I think your idea would work, although the steel would have to be replaced with either a new one of suitable span, or a wooden beam.
I am leaning towards using the wooden beam, connected back to the load bearing lintel, using bits of wood as you suggested.
However, because there is limit clearance between the top of the external wall and the rafters, it can only be a 2x4 resting on its longer side, so it is not very rigid vertically.

Is there any issue with also attaching the beam up into the rafter overhangs, using angled wooden blocks to bridge the gap and screwing through them? This way, there would be plenty of support both vertically and laterally?

Thanks again

Read more: https://www.diynot.com/diy/threads/bifold-structural-opening-issue.558962/#ixzz6g9qIl3h3

 

[Notch7]

So is the timber frame cavity lintel on the outside doing anything?

internally is the double 6 x 2 with angle iron acting as the load to take the rafters?

id be tempted to remove the outer lintel, put in an 8 x 2 horizontal flush to bottom of 6 x 2 inner lintel

then make a packer of say 3 x 2 whatever to sit on top of the 8 x 2 and cut out angled notches to go around rafters -then screw them in firmly

if the 8 x 2 isnt enough to create lateral stability then a steel plate could go across underneath -or instead of an equal angle to strengthen the inner lintel, use an unequal angle.

 

[messtin]

So is the timber frame cavity lintel on the outside doing anything?

internally is the double 6 x 2 with angle iron acting as the load to take the rafters?

id be tempted to remove the outer lintel, put in an 8 x 2 horizontal flush to bottom of 6 x 2 inner lintel

then make a packer of say 3 x 2 whatever to sit on top of the 8 x 2 and cut out angled notches to go around rafters -then screw them in firmly

if the 8 x 2 isnt enough to create lateral stability then a steel plate could go across underneath -or instead of an equal angle to strengthen the inner lintel, use an unequal angle.

Hi Notch, correct on both. the timber frame cavity lintels were doing nothing except giving something for the top of the old window frames to seal against and something for the soffit board to rest on. The sistered 2x6's on the inner wall with the soon to be fitted 150x90 unequal angle iron are supporting the rafters.

Annoyingly, the angle iron was spec'd and ordered before this issue came up, otherwise a longer unequal angle extending to the outer wall would have been a good solution. I think the structural engineers struggled to get their heads around the construction of the existing extension!

But, I quite like your 8x2 option, that could work nicely and I think would give enough stability for the tops of the frame.
My only other thought was if I used multiple noggins to connect the inner lintel to a smaller timber over the doors, I could space the noggins to allow insulation to be installed into the voids between them. But i suppose an 8x2 wouldn't be too bad anyway.

Thanks