Gable end side extension. Is fully open plan feasible?

[trish1400]

Hello,

I've just bought a small post-war semi with cavity walls. I'd like to build a 3m wide x 6.5m long side extension. I will definitely be consulting a SE but before the architect comes around on Friday (and I start telling him my wild ideas and he comes back with wild prices) I'd like to know how feasible it is to make the opening the full width of the house.

Anyway - to set the scene, this is the house:

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• trish1400
• 12 Feb 2014
• 1

and this is current downstairs floor plan:

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• trish1400
• 12 Feb 2014
• 1

All the internal walls are brick but I've marked in red what I think are the internal load bearing walls - these are certainly the walls that correspond with the upstairs and are visible in the loft anyway. There is also some sort of beam (boxed-in in orange pine) between the kitchen and dining area connecting to that half wall - I'm assuming this is structural even thought it doesn't correspond with any walls upstairs. Sorry this is the best photo I have which shows the beam:

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• trish1400
• 12 Feb 2014
• 1

Ok - so my plan is to knock down the outbuildings (which are single brick thick with a tin roof and build a single storey extension with a lean to roof. The floorplan would look something like this:

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• trish1400
• 12 Feb 2014
• 1

Internal load bearing walls and structural beams marked in red again.

I'm assuming putting in a beam to support the full width of the gable end of the house is not going to easy but I would like to know how feasible it is and how many more thousands of pounds it would be compared to only removing half the external wall (e.g. a 3.5metre opening instead of a 6.5m one).

I hope you can give me some guidance - this is my first house and my first experience of a building project and I'm worried that the architect and the SE will take the 'anything is possible' route and I'll get a fright when I get the builder's quotes - so I'd like to be prepared before I met the architect.

Thanks,
Trish

 

[noseall]

You are proposing a 6m wide bi-fold door opening with a beam above which in turn will be supporting a beam carrying half the house, MID SPAN!!!!

I guess if this beam were say 900mm deep then you should be ok.

 

[trish1400]

You are proposing a 6m wide bi-fold door opening with a beam above which in turn will be supporting a beam carrying half the house, MID SPAN!!!!

I guess if this beam were say 900mm deep then you should be ok.

Haha - ok - thanks noseall! That's just the kind of reality check I was hoping for - I hadn't even thought about the doors (I drew them when I was planning on keeping most of the wall).

Ok - so if I had a solid wall at the end. Would that be ok?

Kind of like this? (I know I've now got two pointless sets of bifolds but it's just for illustration purposes)

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• trish1400
• 12 Feb 2014
• 1

 

[tony1851]

It's perfectly feasible. On that span, you would use a 254 x 254 steel, and would need small piers each end for bearings. Foundation would need to be checked for suitability as there will be an increased load there.

The beam could be installed in two sections, with a connecting splice bollted on when the two parts are in position.

It's no big deal.

 

[trish1400]

Excellent, thanks Tony!

Ok, I don't suppose you (or anyone else) knows how much more it would cost compared to keeping say half the external wall?

Or even better would know a ballpark figure for the project? I'm in the Isle of Man so we're probably talking inflated but not London prices (although only 5% vat on installed materials) . I'd budgeted £40k plus contingency for the whole project (but that includes a new bathroom upstairs plus rewiring, new central heating system) at builder spec (I realise there's no designer kitchen in this budget).

Realistic?

 

[noseall]

It's perfectly feasible. On that span, you would use a 254 x 254 steel, and would need small piers each end for bearings. Foundation would need to be checked for suitability as there will be an increased load there.

The beam could be installed in two sections, with a connecting splice bollted on when the two parts are in position.

It's no big deal.

What, even with all the other beams weighting down on it?

 

[tony1851]

What, even with all the other beams weighting down on it?

Yes, as long as the brickwork returns were of adequate size to carry the beam reactions, I would not have a problem.
A 10" x 10"UC is a very sturdy section.

Expense-wise - who knows? 3-4K for the steelwork and supports?

 

[trish1400]

Thanks for the replies guys!

I realised a bit belatedly what noseall wasn't just talking about the bi-fold door beam but also the beam that would be required to replace the existing beam and half wall.

I just went by the house with a crowbar to try to determine once and for all if that boxed in area was hiding a load supporting beam or not. It doesn't line up with any walls upstairs, it seems unlikely there was previously a wall where the beam was, as it would cut right across the doorway and I'm increasingly sure the current layout of the house is the original layout, mainly because the skirting board in the entire house is the same and it's definitely not a standard profile (it looks like miniature coving). I noticed in next door they also had a beam in their kitchen (they don't have a half wall) but I didn't note whether it was in the exact same location. Next door was previously converted in the Doctor's surgery and then changed back to a house - so it's been messed around so much it's difficult to say what was where and these are the only pair of semis around.

Anyway... back on topic. Lack of leverage meant I couldn't get the boxing off (I was balanced on the top of a step stool in my work shoes) but I did manage to wedge it open enough so that I could slide my phone inside and take a photo - like this:

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• trish1400
• 13 Feb 2014
• 1

and.... What is inside the beam is..... *drumroll*

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• trish1400
• 13 Feb 2014
• 1

Absolutely nothing. I was expecting wires or pipes at the very least but nope, completely empty. The ceiling (or rather the woodchip) must have been painted blue at the the time the boxing was put up but that was the most exciting thing in there (I took several photos just in case there was something out of shot but nope, absolutely nothing).

Why anyone would do such a mad thing is beyond me but then why anyone would add those vertical pieces of trim to the wall above the picture rail (see photo is first post) is also beyond me. I guess they just thought it was a 'feature'.

That half wall is still cavity wall thickness (as oppose to all the other internal walls which seem to be single brick) so I suppose that could still be load bearing.

I'll let you know what the guy says tomorrow anyway.

Thanks for your help!