Storage loft above garage door


Old 07-12-13, 11:38 AM
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Storage loft above garage door

I am going to build a garage storage loft above my garage door and I wanted to post my idea to make sure it's within the limits of safe design.

The total span will be 19.5 feet and the depth will be 8 feet. I plan on running 2x8 ledger boards around the three "wall" sides using LedgerLok 5" screws to hold it to the studs (two per stud). For the "open" side, I plan on laminating two 19.5' 2x10 boards with 1/2 inch plywood sandwiched between them for a total width of 3.5". I will place a 4x4 post underneath each end of the beam and lag each post to a stud in the wall. For the joists I will use 2x6 boards spaced 16" apart going in the 8 foot direction (back wall to carrier beam) attaching them with joist hangars.

My main concerns would be that the carrier beam will be enough to carry the weight to the side posts and not sag, requiring the need for a middle post which I cant really have due to the garage door and also that the 2x6 joists @ 16" is enough support for at least 40 lbs psf live load. Should I use 2x8 joists instead? Based on my calculation, using 2x8s would add approximately 150 lbs to the total weight of the loft. It would not be that much more $ to use 2x8 but that's a lot of added weight if in fact it is not needed.

Thanks in advance for your help!
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Old 07-12-13, 10:09 PM
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I think you are wasting $$$, using 2 x 8s for storage space ledgers. I've built a few such storage areas, and used mostly 2 x 4s and occasionally 2 x 6s, for the ledgers. Never had a problem. If you are going to store literally tons of stuff up there, then, yes, use 2 x 8s.

I've made a few other comments on the other (similar) post that you inquired on.
Old 07-13-13, 06:58 AM
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Thanks for responding! As I mentioned below, I'd like to have a live load capacity of 40 lbs/sqft. I will be storing normal household goods, kids toys, seasonal decorations, spare tools, maybe a couple boxes of books or very small furniture (like an end table or coffee table). There will be no bowling balls, portland cement bags, or used engine blocks :-)

For the carrier beam I want to laminate 2 (or 3 if needed) 2x10s with 1/2" plywood sandwiched in between. I will use generous amounts of wood glue for the lamination and then drive 4" screws every foot or so for added strength. This is how others who have built these beams have instructed me to do it, I didnt just make that idea up.

I will use 4x4 post-to-beam brackets to set the beam on top of 4x4s at each end that will be lagged to the wall studs and then tie the beam to the ledgers on each side with angle brackets to keep it all together.

The 2x6 (or 2x8) joists will run in the "short" direction (8 ft) from the back wall ledger to the carrier beam and attached with joist hangers 16" on center.

As I mentioned below, one of my concerns is whether 2x6's are enough. By checking joist span calculators I believe 2x6s over 8 feet at 16" can support plenty more than 40 lbs/sqft and since this approximately 19' span would require 14 of them, switching to 2x8s will add significant weight to the structure (and to the carrier beam's load) which I dont want to add if it isnt needed.

I definitely dont want to do an inverted T with 2x6s over such a long span, but I would like to make sure that 2 2x10 and 1/2" plywood will be enough to prevent sag or whether I need a third 2x10.

I will use 2x12s if absolutely needed, but would like to avoid them because I am already approaching the 3 foot mark in terms of head room for the loft and I dont want to eat up any more space. But if it begins to sag in the middle, it will begin to interfere with the garage door opener.

As far as tying it to the top, I have a second floor above the garage, not roof rafters and my garage has a finished ceiling and is 12' high. I COULD get up there and hunt for floor joists with a stud finder and try to toenail something up there to support the middle, but I'm not sure how successful that endeavor will be.

Your input would be appreciated. Thanks!

Bridgeman45 posted:

I haven't responded, because, quite frankly, I can't possibly give an accurate assessment to something without knowing what kind of loads you will be storing up there, and exactly how, with specifics, the carrier beam and joist support system will be constructed. I have experience building a few (6 or 7) long carrier-beam garage storage areas, and those beams that approached or exceeded a 20' span were made using everything from triple 2 x 12s to an inverted "T" of 2 x 6s. All of them were designed with a center support from above, properly tied in to multiple ceiling joists and roof rafters. The owner of the inverted "T" 2 x 6 design decided at the last minute he didn't want a center support, saying he'd "only be storing light stuff up there." Against my better judgment, I built what he wanted. And of course, just a few months later, he called me and complained about the sag in the middle. I was in the process of moving out of the area at the time, so I expressed my condolences while suggesting a few good carpenters who could help him out.

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