strengthen a header?

I have two 2x10s 18 feet long supported in the middle by one 2x4. Windows are now in these openings. Id like to remove the center 2x4 and replace the windows with a 16x 7 garage door. What size (thickness) flitch plate would be needed to strengthen the 2x10s to support the open span? (Keeping within the 9 height.) Single story, 4/12 roof, rafters are perpendicular to header. No live load, just ceiling joist. Snow load for western NY. Next wall parallel to header is 22feet away.
Thanks TP
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If the 2x4 post supports its maximum load, say 1.5x3.5x1000 = 5250 pounds, the beam might have an equivalent uniform load of 583 lb/ft, according to
http://www.toolbase.org/Docs/MainNav/WoodFrameConstruction/2947_flitchplate.pdf?TrackID=0&CategoryID=1153&DocumentID=2947

You may be out of flitch territory and into something like a 10"x5" I-beam.

Hard to picture that. What's the load on the beam?
You might seek professional help...
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The calculations to determine the individual tributary loads and the resultant header load are pretty straightforward, the flitch plate calculations a little more involved. I don't think you are going to find anyone on a newsgroup (even a PE) who will be willing to give you an absolute answer.
I'd suggest you contact a local engineer...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

And a more complete deescription would be needed-any roof overhangs, roof style, stick or truss framed roof, etc. To many thngs not mentioned.
If I'm not mistaken, a ceiling live load has to be applied to any space with a headroom greater than 42 inches. I would imagine snow load is at least 50 PSF in western NY. The local authority would tell you that value.
Again, call a local...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This is the same info given to the Glulam (paralam) company. They specd 3, 1 1/2x 9 1/2 GluLam beam. I would just like to use steel to bring the 2x10s to the same spec.
Rick wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

OK, at first glance I'd say they calculated the load capacity of the existing configuration and used that to spec a clear span. Maybe I'll run some numbers to check that....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, if two 9' 2x10s have S = 3x9.25^2/6 = 42.8 in^3 and M = 1000S = 42800 in-lb = W9x12/8, W = 3169 pounds, it looks like the 2x4 post (it might support 5250 pounds) isn't the limiting factor. The uniform load on an 18' beam would be 2x3169/18 = 352 pounds per foot.
The 1981 NAHB ap note says an 18' 2x10 Hem Fir beam with a 1/2"x9" plate can support 215 lb/ft of uniform load, so a 0.5x352/215 = 0.82" plate (or 2 246 pound 7/16" plates) might support 352 lb/ft. They suggest 1/2" bolts every 20" near the top and every 40" near the bottom and something like 2 2x6 jack posts with 3/4" plywood plates at each end.
Please apply the usual disclaimers.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

uniform
This was my initial approach, too.
When you calculate the bending stress (Sg.7) and deflection on the glulams specified, (E=1.8E06) with a 352 pounds/foot load, Fb is about 2000 psi (2400 psi allowed) but the deflection is about 0.9 inches, assuming a 16 foot span (garage door width).
If you use the 1/360th of span as the limit, and 16 foot unsupported span you get about 210 pounds/foot.

plate
plate
end.
Ditto
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

the
post
It does meet 1/180 of the span. Still, even 352 pounds per foot is low if the header is supporting a roof. If the opposite wall is 22 feet away, that's only a 32 psf total load.
Oh well....

suggest
and
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks Rick,     I was looking at the other side of the building. It has an 18 opening with the same room dimensions. Of course same roof load. There are three 2x12s supporting the same ceiling attic space. What would be the psf on that span? It has been there for 17 years. Im leaning toward the 3 LVLs (glulam) because I cant seem to get a straight answer on a flitch plate. Seems costly 4.45 per beam, per foot.
TP
Rick wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey Rick, all this time I was comparing between a LVL and adding a flitch plate. Wouldnt three 2x12s support everything and cost one third the price of LVL? Where is the LVL advantage?
TP
TP wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.