New first floor wall supported on bifolding doors??

[indus]

Firstly apologies for the mickey mouse drawings. The planning drawings would have been too confusing and I can't use sketch up etc.

Basically I have a rear single storey extension with a single pitched roof. I want to build a first floor extension that will extend half way across it. The existing rear extension has a large pair of patio doors and a window.

It looks like this



I would like to replace the patio doors and window with bifolding doors all the way across as shown with the dotted lines below.



However my agent said that the wall of the proposed first floor extension would need to be supported on a pier and so bifolding doors aren't possible. He says it needs to be like the drawing below ie two sets of doors with a pier in the middle supporting the wall.



Is there a way to support the new wall but still have bifolding doors all the way across?

Many thanks

 

[Jackrae]

Proper structural engineering design with suitable pier footings and beam across opening. Anything is possible - it just depends on the depth of your pocket.

 

[indus]

Thanks Jack, I suppose I knew anything is possible but wanted to know just how complicated it would be ie if it means basically demolishing the existing rear extension then it's a no go.

Can you expand on what you mean by suitable pier footings? Does that mean the foundations the piers sit on or the interface where the steel sits on the piers?

Thanks

 

[Jackrae]

That's where the professional structural engineer comes into the equation (which I am not).
But, basically, the pillar foundations will be receiving a much greater load than they were designed for and will have to be assessed to determine their suitability. If strong enough then you have no problems, if not, then they will need expanding - either by complete replacement or by underpinning.

 

[indus]

Thanks Jack

I will of course discuss this with a SE, but are you basically saying that if

1) The foundations of the two end piers are 'adequate'

and

2) The appropriate steel is selected

I can have a 6m opening with the upstairs wall sitting slap bang in the middle of it?

Thanks

 

[RonnyRaygun]

Indus, if your single storey extension is fairly new then the footings should be deep enough to sufficiently spread the load.
The piers will also probably be sufficient as far as compressive strength goes, although they will both need to be wide enough to offer some lateral stability.
If it's OK so far then it won't be a problem getting a beam to work, possibly a 254 UC section.

 

[indus]

Thanks Ronny.

Yes the single storey extension is fairly recent. I just needed to know it was something that could be achieved without spending mega bucks. It seems as though it is and so will instruct a SE to design a solution.

Many thanks

 

[tony1851]

Indus;

Within reason, it can be done. This is an extract off a drawing showing one we did 12 months ago. The bifolds were 5.5m. The beam above was a UC section, with plate welded underneath to pick up the outer skin. There were two smaller UBs supporting the flank wall of the 1st floor on to the main beam.

Untitled

• tony1851
• 22 Apr 2013
• 1

(You might have to tip your monitor on its side).

 

[RonnyRaygun]

There were two smaller UBs supporting the flank wall of the 1st floor on to the main beam.

Overdesigning again Tony...

Woody told me he just builds those side walls off the existing flat roof joists

 

[freddiemercurystwin]

Tony you know they have cad nowadays?

 

[tony1851]

Woody told me he just builds those side walls off the existing flat roof joists

Ronny, nothing from that quarter would surprise me.

 

[tony1851]

Tony you know they have cad nowadays?

Errr, what?
As W recently said, that's the 1851.

(or Cr***y Architectural Drawing?)

 

[indus]

Indus;

Within reason, it can be done. This is an extract off a drawing showing one we did 12 months ago. The bifolds were 5.5m. The beam above was a UC section, with plate welded underneath to pick up the outer skin. There were two smaller UBs supporting the flank wall of the 1st floor on to the main beam.

Untitled

• tony1851
• 22 Apr 2013
• 1

(You might have to tip your monitor on its side).

Tony that's perfect and is exactly what I am trying to do, even the dimensions are near identical!

In relation to the beams supporting the flank wall; one end sits on the large beam, does the other end bolt onto the existing rear wall of the house?

Thanks again, that's a really useful drawing for me.

 

[tony1851]

In relation to the beams supporting the flank wall; one end sits on the large beam, does the other end bolt onto the existing rear wall of the house?

No; the other end of the 2 beams supporting the flank wall of the 1st floor extension are supported off a second UC which replaced the original rear wall (client wanted open plan downstairs).
But they could be supported off some brickwork if the rear wall is still in position.
So it can be done, but some SEs don't want the bother of working it out.

What you have to be careful of is deflection. The job in the pic was new-build, so the deflection under the dead load of the structure above was already 'built-in' before the doors were fitted. In your case, as the doors are already in, the SE would need to work out the deflection caused by both the dead load and live load. If it's excessive, the bend in the beam may be sufficient to cause the doors to jam.

 

[indus]

Thanks Tony.

Actually my original wall isn't all there either. The original house is semi open plan to the single storey rear extension. The plan is to knock out the remaining wall and make it completely open plan so there will be additional beams for the flank wall beam to attach to.

On the issue of deflection you say that my doors are already in, but they are not. There are 3m normal patio doors there but they will be removed, the opening widened to about 5.5m and new bifold doors installed. Have I misunderstood you?

Thanks again