My attatched garages ceiling is made of 2×8’s just like the rest of my house. I am putting a bedroom on top. New 3/4 plywood on top of the 2×8’s. The 2×8’s travel about 12 feet till they’re TECO’d to a 2×12 double microlam with a 1/2 steel plate sandwiched in between. My architect wants me to sister a 2×8 onto each side of the existing 2×8. This will be a huge PITA. I don’t understand since my house has 2×8 ceiling joists and living space above and they span the exact same amount. My house and garage run 24′ front to back. I have no problems with bounce or sag in the house. What do you think?
Craig
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http://www.awc.org/technical/spantables/tutorial.htm
bobl Volo, non valeo
Baloney detecter WFR
I wouldn't park my car in that garage.
Edited 11/1/2006 11:39 pm ET by JoeArchitect
huh?
http://www.cwc.ca/design/tools/calcs/SpanCalc_2002/
2x8 at 16" oc for a twelve foot span works for me. I'll drive Joe's car in.
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I believe it was a 24' span, let's take your car.
you guys can get a car in the garage...this is something new...
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I believe it was a 24' span, let's take your car.
He said he has a girder running down the middle; so it's only 12'.
FWIW, sistering the joists doesn't seem a "huge PITA".
ceiling of garage is already sheetrocked with 5/8" sheetrock and has garage door track and opener attatched, as well as several surface mounted 8' flourescent lights on there. Can't do it from above, plywood is already nailed down. Hence the PITA.
Craig
ceiling of garage is already sheetrocked with 5/8" sheetrock
Unfortunately, you can't do the strapping now, either, without incurring a PITA.
Like I said in the previous post, I think you're real close to being within modern "allowable" span.
How does it feel when you walk around on it?
Craig,
Allowable span depends on the spacing of your joists, as well as the species and grade of lumber you have.
Assuming you have 2x8 hemlock #2 @ 16" centers, I think the allowable span would be approximately 11 or 12 feet. So I think you're pretty close to allowable.
For what it's worth, my house was framed with 2x8s on 18" centers. However, the joists had been cut up a bit over the years due to careless remodels, etc. As a result, the floors were a bit springy. With kids running around, the springiness got to be a bit annoying, so I eventually sistered on with 2x10s; now it's very solid.
Since you've already said you can live with a bit of springiness, my guess is that you'd be fine with what you've got.
One other approach would be to install straps to the underside of the joists. That is, nail on some 1x2s, 1x3s, or metal straps perpendicular to the joists and at regular spacing. When one joist is under load, the strapping helps spread the load to the adjacent joists. Others here know more about this process (it seems fairly common back east) and could give you more detail than I.
Edited 11/2/2006 2:22 am ET by Ragnar17