Hi all, came ascross this forum when I searched “how to make a wood beam”. I have a 12′ span that needs to support 800 ibs per lineal foot. Load is the first floor of a 2 story house I’m thinking of building. I’ve looked over span tables for wooden beams from the American Wood Council. What’s the pros and cons of 5 sistered 2×12’s vs 2 stacked 6×6 with a 2×12 on each side? Or some other combination?
I’m really just beyond the entry point of learning the considerations and calculations involved so I’m a clean slate so to speak. Any and all info is appreciated. Info on fastening methods appreciated too!
Thanks in advance…
Jim
Replies
Const. beam
BIG, BIG, BIG difference. Stacking 6 x 6 not good idea. If as you say you are just learning, keep it simple. Connections can be very critical, but if you make sure that the load it equally distributed across the width of the laminated beam, you should not have a connection factor.
You might want to look at LVL's. They are stronger than standard lumber. Go to your local lumber yard/supplier (not big box stores) and they should be able to size a beam for you. And there is steel if you need to keep the size to a minimum..
And alway remember, free advice is worth what you pay for it.
Don't quote me on this, but a quick check at an online design table shows that a 3-1/8 x 12 glulam beam will carry just over 1000 pounds per foot. This is not a large item and can be purchased relatively cheaply and easily. Why would you choose to do anything else? There are so many more aspects to building a house that are way more demanding and deserving of your time.
In general, two pieces side-by-side is as strong as one piece of twice the width.
But stacking two pieces on top of each other is only half as strong as one piece twice as high. Strength is proportional to the square of the height of the piece.
If the two pieces stacked on top of each other are sandwiched between two tall pieces and well-fastened to the two tall pieces then much (but not quite all) of the "lost" strength would be reclaimed. But that's a lot of conditions to fulfill.
Roughly, for your situation (and pretending that wood dimensions are real), if one 2x12 has a strength of 10, 5 2x12s will have a strength of 50, 1 6x6 will have a strength of 9.5, and 2 6x6 plus 2 2x12 will have a strength of 39.
Jim
Your explanation is a bit simple. There's live load and dead on that beam. You mention it carrying the first floor-the beam would only need to account for part of the "whole" load-the exterior walls/foundation would be there to help out. Further, what's holding up the second story etc?
Your best bet is to take your dimensions and floor plan to your local lumberyard-they will be happy to send your specs to their supplier to calculate what's necessary. They generally "overbuild" the answer, but you should also spec the stiffness of the structure you are wishing to build. This is especially true in your joist selection. What works for carpet and the jiggling china cabinet don't necessarily work for stone floor tile.
When you use solid wood species, the species part is also important-different wood, different specs.
I commend you for your efforts though-but do realize the engineering limits that us untrained individuals garner. The positive side is, you won't have that anal quality most enamored by engineers...........
hire an engineer to solve your structural situation
Crisfield wrote:
Any and all info is appreciated.
Jim
Do you mean appreciated as long as it's free? If it's free, chances are it is also just as worthless.
Jim, do yourself a favor and retain the services of a professional engineer to solve your specific structural situation. Even if you get the solution through your local lumberyard (a good, cost effective option) you're compensating an engineer for it by the sale of the material. Free public forums are helpful, but they're definitely are not a substitue for professional engineering services. Besides, the seal that goes along with a professional solution is probably required to get your home building permit anyhow.