RSJ over BiFold Doors

[SysMax]

Trying to cut costs I am myself project managing my ground level single floor wrap around kitchen extension. It's a fairly simple design, no walls are being knocked down.
I have Planning Permission and am now working on the Building Control Plans.
We intend to install bifold doors to stretch over approx 5 meter wall to wall, at the front of the extension. To do this I proposed having a RJS over the doors and spanning the two side walls, then cover the extension with a King Post design roof. Please the the images below.
My question is for Building Regulations approval would I need engineering calculations for this part of the project? Or are there other options?
Many thanks in advance.

 

[jks7492]

It depends what type of lintel you use over the bi-folds.
If you use a suitable size proprietary lintel from a manufacturer then generally no as the manufacturer provides their own standard calculations for the lintels. If you use a steel beam from a steel stockholder then yes you'd be expected to provide calculations from a structural engineer for this.

Did you do the plans yourself or has an architect done them?
A couple of things from looking at your drawings -
The masonry reveals either side of the bi-fold are too short and don't meet building regs.
What do you mean by a king post design roof? A king post is a specific type of truss.

 

[^woody^]

You will need calculations for a steel beam unless your council/inspector accepts certain section sizes for certain spans.
If you can get a standard lintel for that size and loading situation (ie a gable), you should not need calculations

You will need to justify buttressing of the return piers regardless, unless they are 665mm.

Your section drawing is confusing. You would not see the beam or padstones in that section view. It looks like you have another beam and overhanging padstones somewhere else.

Your detail of the drain and foundation is wrong. Foundations should go under and bridged over any drain at that depth. And if its a public sewer, you need your water company's permission before applying to building control

Your reference to wall span and roof span are contradictory - roof span is an internal dimension, and there is no such thing as wall span in this context - its just "width" which is an external dimension, but you would not mention width, just dimension it - and the arrow does not go to the end on the left, BTW - it look like it goes to the internal face.

I don't know what the last drawing is showing as the blue pipe seems to be in a different place compared to the other views

You should label the views

Don't draw horizontal battens on rafter section views. That implies a different roof system.

 

[tony1851]

You wouldn't want a padstone showing on the outside - that would look naff against the brickwork; you would have the bearing of the beam long enough so as not to need a padstone.

You don't need 15mm 'fireproof' plasterboard - standard 9.5mm will do.

Your wall returns at approx. 500mm would need to be justified by the SE as 665mm is the normally accepted minimum. It could be shown that 500 would be OK structurally, but that could well be insufficient to resist any lateral forces from the impact of door-closing - bricks might work loose.

By 'kingpost roof' do you just mean a vaulted roof? If so, ridge would need to be steel (178 x102 might just do it, 203 x 102 better).

The beam over the bifolds could be a standard Catnic or IG lintel, or it might be cheaper to get a fabricated lintel made up - usually a steel beam with plate tack-welded underneath to carry the outer skin.

On that span, something like a 152 x 152 x30 plus an 8mm plate would do.

 

[A_Novice]

How much are you saving by doing the building reg plans yourself? 2k?

Wouldn't it be better to have someone fully qualified to do these? 2k is probably quite a small amount compared to the total project costs.

If you are doing them yourself and BC pass them it still doesn't mean they are any good.

 

[Dereekoo]

How much are you saving by doing the building reg plans yourself? 2k?

Wouldn't it be better to have someone fully qualified to do these? 2k is probably quite a small amount compared to the total project costs.

If you are doing them yourself and BC pass them it still doesn't mean they are any good.

People are very free and easy with other people's money.
If it gets passed its good enough

 

[SysMax]

Hi Guys thanks for the quick replies WOW, very grateful.
Yes this is my first attempt at doing plans of any type, so I can take any criticism on the chin. I did same with the Planning permission plans using SweetHome3D. I've never seen an approved plan before, just images on the net.
I haven't decided on moving forward via the Building Notice or Full Plans route yet, I'm hoping to understand every aspect of the building methods
before handing the work to the builder. Anyway I'll show them to our builder before submission.
For the long lintel, watch the end portion of this video

It depends what type of lintel you use over the bi-folds.
If you use a suitable size proprietary lintel from a manufacturer then generally no as the manufacturer provides their own standard calculations for the lintels. If you use a steel beam from a steel stockholder then yes you'd be expected to provide calculations from a structural engineer for this.

Did you do the plans yourself or has an architect done them?
A couple of things from looking at your drawings -
The masonry reveals either side of the bi-fold are too short and don't meet building regs.
What do you mean by a king post design roof? A king post is a specific type of truss.

I'm going to contact some proprietary lintel manufacturers and see.
Will increase wall returns to 665mm.
Correct roof design should be Vaulted.
thanks jks7492

You will need calculations for a steel beam unless your council/inspector accepts certain section sizes for certain spans.
If you can get a standard lintel for that size and loading situation (ie a gable), you should not need calculations

You will need to justify buttressing of the return piers regardless, unless they are 665mm.

Your section drawing is confusing. You would not see the beam or padstones in that section view. It looks like you have another beam and overhanging padstones somewhere else.

Your detail of the drain and foundation is wrong. Foundations should go under and bridged over any drain at that depth. And if its a public sewer, you need your water company's permission before applying to building control

Your reference to wall span and roof span are contradictory - roof span is an internal dimension, and there is no such thing as wall span in this context - its just "width" which is an external dimension, but you would not mention width, just dimension it - and the arrow does not go to the end on the left, BTW - it look like it goes to the internal face.

I don't know what the last drawing is showing as the blue pipe seems to be in a different place compared to the other views

You should label the views

Don't draw horizontal battens on rafter section views. That implies a different roof system.

Thanks Woody

Yes that section view is confusing will delete that one and keep 1st cross section and completed view only. The pad stones won't be on show.
Will follow your advice on roof battens, editing the referencing and arrows on the drawing and increase return piers to 665mm.
I haven't managed to find a standard lintel over 4M! 3.6M yes, Catnic CG90/100 open back cavity wall lintel.

I'm not to clear on your advice regarding the drains though.
The blue pipe is a combined drain (rain water and dirty kitchen/bathroom water, old original pipes). It is at clay level aprox 90cm down from original house DPC.
The yellow pipe is a separate raw sewage toilet drain, can't see manhole for that (same for all houses on our terrace btw). Are you saying there should be no gaps in the footings? The concrete should flow completely around and under the pipes?
I'm aware of the water authority point though.

You wouldn't want a padstone showing on the outside - that would look naff against the brickwork; you would have the bearing of the beam long enough so as not to need a padstone.

You don't need 15mm 'fireproof' plasterboard - standard 9.5mm will do.

Your wall returns at approx. 500mm would need to be justified by the SE as 665mm is the normally accepted minimum. It could be shown that 500 would be OK structurally, but that could well be insufficient to resist any lateral forces from the impact of door-closing - bricks might work loose.

By 'kingpost roof' do you just mean a vaulted roof? If so, ridge would need to be steel (178 x102 might just do it, 203 x 102 better).

The beam over the bifolds could be a standard Catnic or IG lintel, or it might be cheaper to get a fabricated lintel made up - usually a steel beam with plate tack-welded underneath to carry the outer skin.

On that span, something like a 152 x 152 x30 plus an 8mm plate would do.

Thanks tony1851

All your points well noted including the plasterboard and roof vaulted roof advice. I will research some companies for a suitable lintel.
No, padstones and lintel will not be visible lol, my fault for not being clear on the drawings, was trying to explain the masonry returns width.

How much are you saving by doing the building reg plans yourself? 2k?

Wouldn't it be better to have someone fully qualified to do these? 2k is probably quite a small amount compared to the total project costs.

If you are doing them yourself and BC pass them it still doesn't mean they are any good.

Thanks A_Novice

My missus is the tight one here lol. Saving money where possible is why I'm here son. That 2K will go a long way for the doors or bricks and mortar. I will go over the plans (when I've completed them) with my builder before submitting the plans, for clarity.

Great thanks guys.

 

[^woody^]

I'm not to clear on your advice regarding the drains though.

The rear section view shows a blue pipe passing through both foundations

The last but one side view shows a blue pipe near the outer edge of the extension

The last view (presumably a 180° flip of the view next to it) shows a blue pipe near the house, not the where it is shown on the view next to it

You also say the pipe is about 90cm down from DPC, but on the drawing it looks a lot higher up. You should really show it at the correct depth as that will determine how the pipe is bridged and the foundation detailed around it. Otherwise the inspector will question it, and you will say "oh the drain is really deeper than that"

And you would be wise to show the existing house foundations deeper, to avoid the inspector questioning that, and avoid PW Act issues.

 

[Dereekoo]

"I haven't managed to find a standard lintel over 4M! 3.6M yes, Catnic CG90/100 open back cavity wall lintel."?????

Catnic CX90/100 Extra Heavy Duty Cavity Wall Lintels « Condell Ltd (condell-ltd.com)

 

[SysMax]

The rear section view shows a blue pipe passing through both foundations

The last but one side view shows a blue pipe near the outer edge of the extension

The last view (presumably a 180° flip of the view next to it) shows a blue pipe near the house, not the where it is shown on the view next to it

You also say the pipe is about 90cm down from DPC, but on the drawing it looks a lot higher up. You should really show it at the correct depth as that will determine how the pipe is bridged and the foundation detailed around it. Otherwise the inspector will question it, and you will say "oh the drain is really deeper than that"

And you would be wise to show the existing house foundations deeper, to avoid the inspector questioning that, and avoid PW Act issues.

Thanks woody,

Yes your right, I have to edit the underground drainage part of the drawings. I've uploaded a drawing I made for my reference and will follow your advice. Our house is an end of terrace semi.

 

[SysMax]

"I haven't managed to find a standard lintel over 4M! 3.6M yes, Catnic CG90/100 open back cavity wall lintel."?????

Catnic CX90/100 Extra Heavy Duty Cavity Wall Lintels « Condell Ltd (condell-ltd.com)

Thanks Dereekoo,
The Catnic CX90/100 4575mm or Catnic CX90/100 4200mm
Exactly what I need.
So, I may not need an engineers calculations for this lintel as it's a proprietary lintel from a manufacturer?

 

[^woody^]

So, I may not need an engineers calculations with this lintel?

and loading situation (ie a gable)

You should ask the manufacturer to confirm. Its not just about the weight on the lintel.

As for the drains, you really need to be drawing them as straight lines between the points, not with loads of bends like that. Also, have you confirmed that your council will allow new rainwater and surface water connections to the existing system?

 

[SysMax]

You should ask the manufacturer to confirm. Its not just about the weight on the lintel.

As for the drains, you really need to be drawing them as straight lines between the points, not with loads of bends like that. Also, have you confirmed that your council will allow new rainwater and surface water connections to the existing system?

Thanks woody,
Will confirm with lintel manufacturer.
Yes, it is strange, I wondered about it. All the houses on our terrace seem to have the same drainage system and we're first on that combined drain. I've dug out this drain to have a close look. It looks like at some stage in the past (decades) bath and kitchen water was diverted into the storm drain along the whole street! I will check with council though, maybe I will have to redivert to the foul main sewer.