Multiple doors and headers

[BobsF85]

I just finished pouring the concrete for my new garage Fri. and I'm getting ready to buy the lumber. The garage is a 26 X 34 with 10' walls/ceiling height and attic trusses to allow a 15'X34' bonus room/man cave over top at 40Psf.

The design is a drive thru style garage with doors on both sides. The doors are on the eave side in the bearing wall. I am planning to park 2 cars and a boat in it. There will be a 16'X8 garage door on front and back and a 10X8 garage door front and back. Eventually the one end of the garage will be buttressed with a 8'X26' workbench area to house stationary compressor, table saw, drill press etc. etc. This will also serve as the service entrance with a 36" door front and back. Access to the attic will be via a outside stairs and deck at second level.

I have arrived at using 2- 16"X1-3/4" LVL's X2 for the 16' garage door spans. The 10' span can be done with 2- 9-1/4" LVLs. In discussing this with a friend over the weekend he said many locales were now requiring the header to be continuous when spanning multiple doors. I had not heard this before but it did get me thinking that from a framing perspective it might be easier to just run 2-30' 16" LVL's, uninterrupted across both doors and then add the support wall in underneath to divide it into 16' and 10' bays. It would not add significant cost to the project and might be handy down the road if I ever decided to reconfigure doors or had to get something big in or out, the center support could temporarily be removed. Any reason not to do this other than cost?

Configuration is roughly:
| 3'wall |_________16'door_______|2'wall|_____10'door_____| 3'wall |

 

[pattenp]

None, other than having to handle and set a 30' LVL.

 

[Jeff Ivers]

I will be watching this to see what the experts say. I have a similar setup, built in 1990, with a 24x50 dimension and 2 16x 8 doors on one eave wall and one 16x8 on the opposite wall. I was advised to use solid wood headers - 4x16 fir. I am quite happy with how the shop has held together, but those headers were heavy and posed an interesting challenge to erect. I an unfamiliar with the engineering specs on LVLs but wonder if a 16" one will support the necessary load when extended to 30 ft.

 

[mbatarga]

but wonder if a 16" one will support the necessary load when extended to 30 ft.

They are doubled up - 2 thick.

 

[Blk88GT]

Interesting idea. I did 3 separate sections of LVL along one wall for my doors. It wasn't too bad to lift, but we were using a zoom boom as it's a 50' x 12' wall.

 

[BobsF85]

Just to clarify, I don't intend for the LVLs to support the load of the entire 28' span. The 2 foot wide section of wall under the level and between the 16' and 10' doors will be considered load bearing. Any removal or modification would be temporary and alternative support measures taken.

LVL's will be raised one at a time and set on wall then glued nailed and screwed. I figure 1 16"X 1-3/4" X30' LVL would be manageable. If need be I can use the neighbors FEL to assist.

In my mind, using a continuous beam and adding more length across bearing points will make the entire assembly stronger and more rigid with less chance for issues if something ran into the mid span support by accident.

 

[Zeke]

You get more lateral stiffness with a continuous header. Depending on the width of the center wall section and how many trusses sit on it, this could be a benefit.

 

[PugetDude]

^^^this^^^

 

[kbs2244]

Do a cost comparison with a steel beam.

 

[BobsF85]

Here is the cost comparison with the steel beam. 1-16"X 1-3/4" X 30' LVL is $178.20 at Menards. I would need 4 for a total cost of $712.80. The calcs are readily accepted by my LAHJ at 31,650lbs for 16' span for this using 2 LVLS and there are no special considerations needed for attachment or posts. Weight needed to be lifted is 8lbs per linear foot or 240lbs total. This can be done easily by 3 men on ladders or with a FEL on tractor. Total weight bearing on walls is 480lbs.


Using steel, a W8X21 is rated for a 16'span. At $1.20lb this works out to $756.00 per beam for a total of $1512.00. At 21 lbs.ft. we would need to be able to lift 630lbs.
The tractor might do this but forget doing it with less than 6 men on ladders. The W8x21 is rated at 18,200lbs/ft at 16 foot span. I would need an engineers sign off on the steel and support system and would likely need steel posts fabricated with brackets and have to drill beam for attachment. After that I still need to wrap it in wood at an additional cost of materials and labor. Lumber yard will deliver my order free, Steel supplier will not. No cutting fee for lumber yard, cutting fee for steel.

No gain here in my book. LVL wins hands down. Cost,weight, ease of assembly etc. Steel would only be competitive if I could find it at scrap cost.

I also priced this out using two separate headers by Metwood. Quote came in at $1588.14 plus tax and $75.00 delivery. No gain there either.