Concrete sectional garage - roof joists, lintels question

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hi, currently have a concrete sectional triple garage that I'm removing the fibre concrete asbestos roof and replacing with plastisol coated 0.7mm steel.

I'd like to turn the three garages 8ft door and two 7ft 6" doors into one double and a workshop.

Current roof joists are timber 150 x 47mm on hangers, at 120cm spacing. Each is the width of each garage.

I think from reading building regs, I need 225mm x 47mm at 600mm spacing if I'm to span the width of a double garage, which seems a lot compared with what's there now. But ok if that's what it needs.

But then I got thinking about the lintel over the door and a lintel to span a 4.5m width approx will be huge.

Am I looking at this wrong for what is just a prefab garage? Any recommendations for joist and lintel sizes?

Simon
 
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If ever the term putting lipstick on a pig or polishing a turd were more apt.......:eek:

These garages are usually stiffened up when the lightweight roof structure is bolted in place. This occurs when the metal trusses are bolted to the side sections and the roof sheets are fixed to the metal purlins slung between the trusses.
Happy days.

What you are proposing is making the structure top heavy (timber wise) without considering what is going on below. My guess is that you would be better off constructing a timber shell within the concrete garage and put the roof on that, rather than faffing about with something that is designed as a 'low end' building.
 
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Ha - it's funny, was just using the lipstick on a pig expression with a mate to describe what I'm doing. There are no steel trusses - it just has timbers. I think what I'm going to do is refurb the two doors on the centre and right and put a stud wall and cladding on the workshop garage. New steel roof and add additional joists at 600 centres. For about 1 k, I get a weather proofed structure that looks less shabby than before. And a workshop. Long term it will come down, but I need somewhere to work while I'm doing the house up.
 
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Whatever you do, be aware that the walls on the roof for stability and vice versa. it is a tenuous arrangement that does not take a lot to destabilise.

Tread carefully with your house of cards....:cautious:
 
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It's been standing like this for around 30 years at a guess. In Scotland, with snow, wind, rain etc. I'm lightening the roof load and strengthening the structure....
 
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It's been standing like this for around 30 years at a guess. In Scotland, with snow, wind, rain etc. I'm lightening the roof load and strengthening the structure....
Turning three compact sectional garages into one large one is definitely not strengthening.
 
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I've never said that's what I'm doing.
Oh.
must have interpreted this wrong...
I'd like to turn the three garages 8ft door and two 7ft 6" doors into one double and a workshop.
What are you doing then?
These structures do not lend themselves well to being knocked about. They are budget, low end buildings and are inherently unstable once you start removing key components. You certainly cant start making large openings in them and expect to lintel over like you would in a normal brick/block structure.
 
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Turning three compact sectional garages into one large one is definitely not strengthening.

This is what I never said, but somehow you have concluded this.

Three garages into a double and a single is not one large one. Double sectional garages exist and I've seen double plus single online. Nonetheless after your lipstick on a pig jibe, In my second post, i said I'd just refurb the doors and put a stud wall on the workshop garage - which left it as three spaces. Then you described it as a pack of cards, but it is as it was erected, which has survived thirty years.

Some of us can't afford or dont need to replace what is serving a useful function. These are low end buildings, ugly, yes but they serve a purpose, and for me, I don't want, and can't afford, to put up a new garage, now. I'd rather save and make do than borrow. I can live with my low end, budget, lipstick wearing pig until the garage is a priority for me. It would have been nice to have had a double space because the turning space in front is tight, and a double would make the car part infinitely more usable. Anyway, all I want is a weathertight structure and a new roof should do that.
 
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Turning three compact sectional garages into one large one is definitely not strengthening.

This is what I never said, but somehow you have concluded this.
Do you wanna highlight this for a third time or didn't you bother to read my above post, i.e......
Oh.
must have interpreted this wrong.....What are you doing then?

My guess is that you intended doing something similar in principle, i.e. knocking about pre-fab garages.
 
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