18′ garage header, how big a header?
alwaysoverbudget
| Posted in Construction Techniques on
framing up a garage door, 18′ wide and will carry the 5/12 rafters on 2′ center,240lb a sq shingles.i’m planning on 3-2x12s with 2 plys of 7/16 ply sandwiched in between.also,i’m not sure if this helps much ,but sitting on top of the header will be 3-2×6’s to fill in to the top plate. hows this sound,will it work or sag like a old horse? suggestions? thanks larry
hand me the chainsaw, i need to trim the casing just a hair.
Replies
Probably sag a bit - but you haven't yet said what the liveload requirement is in your area, only a part of what the dead load will be.
For instance, if the rafters cover twenty feet or ten feet or fifty feet, half of that area will land on that same header. You've only said the length of the header, and not the depth of the are.
Then re live load - some places are fine allowing for 25#/foot while others require 110# or more.
We're talking some big variables here. I would figure the loads exactly and take it to the yard where they can size an LVL for me
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your right i did miss the size of garage. it's 26' so 13 is resting on header.i believe it's a 25 lb load per ft. here in ks we don't have much snow to worry about. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
I'm thinking a piece of steel - maybe a W12x19 I-beam. I don't think the 2x12s can span 18'.
Sandwiching glued and nailed plywood between 2 X stock has worked well for me, although there's probably lotsa variables connected with the quality of the plywood. But I'd like to interject another thought here. How about turning problems like that 18-ft span over to a professional who will take on legal responsibity for the design via an engineer's stamp of approval. There's beauty & precision in having things done exactly right. And exactly right in this case may require a few hours of a structural professional's time.
2x12's will sag with time...and ply helps some, but......................
Go to your local building materials supplier and ask for a wooden LVL or laminated garage door header.
There are manufacturer's tables available to size your header as per your load and span....order and install.
No gluing, laminating & hoping...no torch, grinder & welder....just good carpentry!
.............Iron Helix
According to the span tables in an LVL pamphlet I have, it looks like a 5 1/4 x 16" or 5 1/4 x 18" LVL will work.
Mike
How come your plans don't give you the size?
my 7"x7" napkin doesn't have any specs,guess i'll have to get a better design team! lol larry
hand me the chainsaw, i need to trim the casing just a hair.
You didn't say whether you have a structural ridge. When you said the size of the garage is 26' thus the rafter span is 13', it got us some, but not all, the info we need in order to help you size your header.
If the roof is trussed, or if you haven't a post-supported structural ridge, then your rafters are bringing twice the load to your headers, as compared with a structural ridge situation.
Gene Davis, Davis Housewrights, Inc., Lake Placid, NY
I have an 18 foot garage door, and considered similar solutions. The best one,which has performed perfectly, was 2 LVLs, 11 7/8 deep. No muss, no fuss.
Do you have the same loading that the always overbudget has?I'm no PE, but I am surprised that a 3.5"x12" LVL can span 18' w/o deflecting more than is allowed.
Jon Blakemore
2X12s at that span are undersized. I'm thinking you're looking at 16" or 18" LVLs.
Like somebody said, a lumberyard will size a beam for ya or know how to get it done.
I agree with Boss.
even 4-2x12's are insufficient for that span.
Yea, three 2x12's are unlikely to cut it.
A very rough, napkin-scribble estimation goes something like this: most span tables say doubled 2x12's are good for 12' openings. You have 18', which is 50% wider. Thus, the header will need to be 1.5x1.5=2.25 stronger than the one for a 12' opening. This models the header as a beam with uniform loading, with the same per-foot loading for both header2.
So you'd need 2.25x2~=five 2x12's. You have run through the "real" engineering number for strength and deflection, but this type of estimation will at least tell you if you're idea is even in the ballpark. If there is a point load due to a support for a structural ridge, it'll need to be beefier still.
I agree that you're probably looking at some type of engineered lumber beam.
ok,so you guys got me thinking i'm headed the wrong way,so this am i call my inspector,with a 20lb load [thats whats required here] he said 3 -2x12's were only good for 10.5 feet! so i called my local lumber yard and they figured it needed a 3.5x14 parralam. so thats what i put in,it does have 1 2x12 sisterd to it so that i would flush out to the 2x6 walls. i don't think it really adds much to the capacity but needed to fir out with something. i would of liked to step up to a 16" but it was another 160.00 so i stuck with 14". thanks guys for pointing out how far outa wack this was going to be. i was just kinda flying by the seat of my pants on this,basing it on 30 yr old garages with 16' doors with 2-2x12,before all this engineered stuff come along. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Flying by the seat of your pants makes for rough landings if you forget to drop the landing gear. Good thing you asked for a visual check on it, LOL20# load??? He must have been refering to live load. Dead load alone runs about 10-15#/sf
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i thought 20lb sounded lite,but he mention that counted snow load. we don't get a lot of snow, sometimes 5-6" then gone in a couple days, but 5 inches of snow has to start pushing the 20lb,heck a good frost might do it! thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Go here http://www.trusjoist.com/PDFFiles/2020.pdf for LVL header sizing.
Your answer can be found on page 4.
Gene Davis, Davis Housewrights, Inc., Lake Placid, NY
Edited 5/24/2005 4:50 pm ET by Ima Wannabe
great website. i booked marked it so next time i'll know where to look! thanks larryhand me the chainsaw, i need to trim the casing just a hair.
I had a 16" GD opening recently that I had to remove the threee 2x12's w/ ply in between and substitute (3) 1 3/4"x12" LVL's for because the inspector said the original was not up to code. If you want to build it right, go with the LVLs; I have seen too many garage door openings sagging after 10-15 years. I've even seen (2) 1 3/4"x12" LVL headers in a 2x4 garage door wall sag while we were framing the house! And that's with a 7/12 hip roof, avg. 11' run, 20-year shingles, and no snow load whatsoever.
Jason Pharez Construction
Framing & Exterior Remodeling
I built a box beam header for mine that seems to have worked well. I forgot the website that had designs for various spans and loads, but the building of it was fairly straightforward and inexpensive (it is basically a 2x4 framed short wall wrapped with 1/2" osb and nailed almost every inch with box nails [my nail gun tended to set them too deeply, so I hammered by hand]).