Modifying roof trusses to support living space
#18
  Re: RE: Modifying roof trusses to support living space by Snipe Hunter ([quote='srv52761' pi...)
(10-11-2020, 06:41 PM)Snipe Hunter Wrote: I have one in the middle of a 2 car garage. Dumb. One of these days I'd like it gone. Can't open the car doors.

My father-in-laws garage was like that.   I loaned my then girlfriend my ‘68 Camaro to drive home to Iowa from Indiana.  She returned it with a ding from the post.
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#19
  Re: RE: Modifying roof trusses to support living space by Snipe Hunter ([quote='srv52761' pi...)
(10-11-2020, 06:41 PM)Snipe Hunter Wrote: I have one in the middle of a 2 car garage. Dumb. One of these days I'd like it gone. Can't open the car doors.

Here's a free tip (that we did in our garage):

Wrap the column with some old carpeting and tape it....no more door dings!!!
Dumber than I appear
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#20
  Re: RE: Modifying roof trusses to support living space by Snipe Hunter ([quote='srv52761' pi...)
(10-11-2020, 06:41 PM)Snipe Hunter Wrote: I have one in the middle of a 2 car garage. Dumb. One of these days I'd like it gone. Can't open the car doors.

Got one of those two and hate it. Column supports a steel beam that I thought was strong enough on its own. But since we have a bedroom above the garage the county made the builder install the column, I suppose for fire reasons.
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#21
  Re: RE: Modifying roof trusses to support living space by joe1086 ([quote='Snipe Hunter...)
(10-12-2020, 10:44 AM)joe1086 Wrote: Got one of those two and hate it. Column supports a steel beam that I thought was strong enough on its own. But since we have a bedroom above the garage the county made the builder install the column, I suppose for fire reasons.

Might also be for deflection.  Maximum floor deflection values from live loads is spec'd in the building codes (I'm pretty sure), and while a beam may be more than strong enough for dead and live loads, it may flex too much.  A short increase in unsupported length makes for a small(ish) increase in bending stress, but a large increase in deflection for a given load change.  


I went through the exercise in my basement game room, which has two columns on one long beam.  I'd have to sister a substantial C-channel on each side to stiffen it enough for a single column at mid-span, without cover plating the top and bottom flanges, which would be essentially impossible with joists sitting on the top flange.  Not worth the trouble for my situation.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#22
  Re: RE: Modifying roof trusses to support living space by TDKPE ([quote='joe1086' pid...)
(10-12-2020, 10:53 AM)TDKPE Wrote: Might also be for deflection.  Maximum floor deflection values from live loads is spec'd in the building codes (I'm pretty sure), and while a beam may be more than strong enough for dead and live loads, it may flex too much.  A short increase in unsupported length makes for a small(ish) increase in bending stress, but a large increase in deflection for a given load change.  


I went through the exercise in my basement game room, which has two columns on one long beam.  I'd have to sister a substantial C-channel on each side to stiffen it enough for a single column at mid-span, without cover plating the top and bottom flanges, which would be essentially impossible with joists sitting on the top flange.  Not worth the trouble for my situation.

Thanks for that. After 30 years we've learned to live with it...and open car doors carefully.
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#23
  Re: Modifying roof trusses to support living space by FS7 (I know this is a com...)
I did not intend to start an argument about engineering or permitting. As mentioned, I have done the engineering analysis and was actually given several options. Building trusses in place is fine as the additional load on the wall is well within spec (it seems to be random whether homes done by the builder have attic trusses or web trusses). No columns are necessary with 2x12, though I will be adding more joists (approximately double). It might be cost-prohibitive - it is now because of materials costs, but in the future it might make more sense to actually just replace the trusses. As of right now building attic trusses in place is the least intrusive option if not the cheapest. 

As an aside it is quite fascinating how common this is in the UK (many contractors seem to specialize in it) while simultaneously being relatively uncommon here.
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#24
  Re: Modifying roof trusses to support living space by FS7 (I know this is a com...)
Interesting note...

It looks like I can get trusses (real attic trusses) for about $300 (even with current prices). Regular price, about $100. To build a new truss in place, I'd be looking at about $200 in lumber (minimum) plus fasteners and hardware. Given that I would need to go 12" OC (compared to 24" with existing trusses) along with three doubled, the materials cost is much higher (about 50%). It wouldn't be cheap to tear off and re-roof the garage, but my father in law owns a roofing company and it seems like any time in the immediate future it's going to be cheaper to do this "properly" rather than retrofit. It may never be worth it in that regard as the truss cost plummets when materials cost go back to normal as well.

Maybe that's why people don't do this much. Not worth it.
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