Do I Need To Beef Up My Garage Ceiling Joists? - Building & Construction - DIY Chatroom Home Improvement Forum

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Old 03-03-2012, 11:13 AM   #1
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Do I need to beef up my garage ceiling joists?

My house was built in 1957. The garage (24'-long, 20' wide) only has 3 ceiling joists, 6' apart. I am planning to put a storage space up there between the two joists using a piece of 3/4" plywood (see photos). I expect no more than 200 lbs of stuffs will be up there - mostly my son's used toys.

Do I need to put two more ceiling joists beneath the plywood?

If I do need, then how? Do I need to take off the beam that supports the garage door opener rail? Can I use two 12' long 2x6 pieces and join them together for this purpose?
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Last edited by htabbas; 03-03-2012 at 11:18 AM.
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Old 03-03-2012, 12:58 PM   #2
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tough call for someone from afar. i'd either have an engineer look at it, or, if you like to gamble, put a tight wire below the truss, measure its present deflection, and then watch it every few weeks to see if it is bowing. you are, of course, assuming it will bend before failure, and that may be a precarious assumption. a good carpenter should be able to add a similar truss in there w/out gross expense. have a local cat look at it, though.


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Old 03-03-2012, 01:17 PM   #3
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If the roof trusses are spaced at 6 feet on center, and properly designed to support a 6 foot wide width of the roof, then additional ties are not needed as far as roof rafter thrust is concerned. In that case, you would add the ceiling joists solely to support your storage loads.

If the roof ridge is sagging, as is the case with many older garages, you probably need to add ceiling joists across every rafter pair. (as is specified in the International Residential Code)

The roof pitch looks shallow, which results in a larger amount of horizontal force from rafter thrust.

Most of the old garages I see have sagging roofs and walls bowing outward as a result of a lack of ceiling joists to resist horizontal rafter thrust.
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Old 03-03-2012, 11:05 PM   #4
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Those look like rafters with a ridge board to me. Someone added diagonal struts to help carry the over-spanned rafter tie you have the plywood on. They also added purlins (more weight) without the struts, so it appears. Holding a straight-edge piece of paper up in front of my screen, it appears the closest tie is sagging 2-3" in its length and the second one = 4-5". I've installed those garage doors before and there is a fair amount of weight loading that center tie when the door is open. Remove the plywood..... please.

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