PDA

View Full Version : Double 2x8 header span?


CThomp
08-28-2006, 09:19 AM
The span I have is 9ft. If I use 2x8's and double up on the jacks can I get away with it? We just used 2x8's for headers in another spot and we're trying to keep the look the same. This is for a load bearing wall one story building.

Don_P
08-28-2006, 04:25 PM
Not enough info to get the load,
Have you tried this chart? From your location I'd click over to the US species chart and use SYP, it'll get you farther.
http://www.cwc.ca/design/tools/calcs/SpanCalc_2002/span_calc_headers.php?member_type=999&species=0&grade=0&height=2&width=4&spacing=12&load_id=0&result=&span_type=1

CThomp
08-29-2006, 04:34 AM
I new 2x8's weren't going to be big enough.

Thanks for your help.

Don_P
08-29-2006, 06:46 PM
Close enough for LVL's? They're stronger than SYP.

CThomp
08-30-2006, 05:21 AM
Where can you buy lvl's?

CThomp
08-30-2006, 05:27 AM
I know LP makes lvl's. But what size would I need? Off the top of my head the length of the span is between 8 and 9ft. I know it needs to be 3.5" thick to match the stud walls.

David
08-30-2006, 05:55 AM
Don't you have a lumberyard you can order from? Otherwise, try Lowe's or HD and ask them to order one.

CThomp
08-30-2006, 06:01 AM
I'm sure 84 lumber carries them. Finding the lvl won't be an issue. At first I thought finding them woulld be hard but I doubt it now. I just don't know what size i'll need.

The total length of the wall in question is about 36'. The span to be covered is 8' heavy. The thickness can't be greater than 3.5".

From some of the charts i've looked at a 3.5" thick by 5.25" tall lvl would actually due the job just fine. But i'd like to be sure.

CThomp
08-30-2006, 07:01 AM
I think i'll have better luck finding a 1.75" x 7.25". I called 84 lumber and their sizes started at 1.75" x 11.25". I don't think what i'm doing will require that.

CThomp
08-30-2006, 07:11 AM
I just talked to a friend in the business who said I can get away with double 2x10's with double studs and double trimmers. He said to sandwich the 1/2 ply between the boards with PL2000 and let it cure really well. Then nail it at 8" increments.

Don_P
08-30-2006, 05:33 PM
It may well be that the double 2x10's are up to the job. I ned to pick a point with the subfloor glue though. Subfloor glue is not structural and adds zero to a beam or headers strength. Reason being it is an elastic glue that creeps under load. The lumber is all you figure on, go back to that header chart and confirm what he recommended for yourself, it was simply a double 2x10 header. Another way is to sandwich a 1/2" thick steel flitch plate between your 2- 2x's.

CThomp
08-31-2006, 04:31 AM
Where do you get a 1/2" steel flitch plate?

Is there a glue that would be well suited to make the header?

Thank you for your responses by the way.

Don_P
08-31-2006, 04:24 PM
Letting a carpenter talk shop, my thanks to you.

There really isn't a way to make a reliable field glue joint, not one that I'd want to count on. Boston tunnel, failed epoxy, engineered connection. A bolted or nailed connection that is also glued can only count on the fasteners. Plywood is also not counted in the calculations of a header. The 2 boards are doing the work, gluing them together face to face would not change their design values, they do need to be well attached to each other for lateral stability. I'm not saying that gluing is a bad idea, it just doesn't change the header's strength, its still just 2-2x's carrying the load.
The flitch plate can be gotten from a steel supplier. The design is beyond me, you'll need an engineer to spec it unless you can google up a safe load table.
The steel is providing the bending strength and stiffness, the wood side plates give the relatively thin plate stability from buckling. From there you could start looking into C channel or I beam, that gets back into standard safe load tables in the AISC manual.

David
09-01-2006, 04:55 AM
I was very interested in this yesterday, so I googled it myself and found this document. Perhaps it will help:
http://toolbase.org/PDF/DesignGuides/flitchplate.pdf

CThomp
09-01-2006, 09:02 AM
I think i'm going to go with the regular 2x10 header and the double stud/double trimmer set up. There is a room behind the bearing wall that had been enclosed for a laundry room/water heater room. The distance from the bearing wall where the header will be to that exterior wall of the small room is only 5ft. That laundry area is being transformed into a breakfast nook. What I can do is attach some 16ft 2x6's to the existing 2x6 rafters and run them out to the exterior wall of the eating nook. My ceiling joist/rafter setup is very adequate according to all the tables i've seen. Wouldn't this transfer a sizeable portion of the load the bearing wall had been supporting to the back wall of eating nook?

That exterior wall for the eating nook used to be a small back stoop.

I've checked all the other headers I've installed so far against the tables and i'm in good shape otherwise.

The pitch of the roof for the breakfast nook is the same pitch as the the rest of the roof. The floor is 6" lower. We'll be raising the floor up to the same height. It will have less ceiling height I know but the room will be a low traffic room for sitting and eating. Not dancing.

Don_P
09-01-2006, 04:04 PM
And there's my reward,
David... Awesome, Thanks!

CThomp,
I'm having a hard time visualizing, from the sound of it though I think I'd be consevative and count on full load at the bearing header.
That pdf gives a good description of how to determine loads. The first 7-8 pages is good general reading.

CThomp
09-05-2006, 06:28 AM
We opted for a double 2x12 header. Better safe than sorry.

Heavy as hell but fit like a glove.