Span for 3x10 pine header?

[cockeyedMFer]

Sorry if this is the wrong forum, but I'll try here first.

Has anyone worked with 3x10 lumber before? I lucked into some beautiful pine 3x10x16 beams, #1 s4s untreated. I'd like to use them as headers on my 32x12' storage loft project.

Problem is that span tables no longer list 3x10, but years ago this size was common in homes and barns.

I was thinking of sistering 2 3x10's to span 16' centers, supported by 6x6 posts. Alternately it could be done on 12' centers but I'd prefer the longest clear span possible.

What do you guys think?

 

[turnkey4099]

Sorry if this is the wrong forum, but I'll try here first.

Has anyone worked with 3x10 lumber before? I lucked into some beautiful pine 3x10x16 beams, #1 s4s untreated. I'd like to use them as headers on my 32x12' storage loft project.

Problem is that span tables no longer list 3x10, but years ago this size was common in homes and barns.

I was thinking of sistering 2 3x10's to span 16' centers, supported by 6x6 posts. Alternately it could be done on 12' centers but I'd prefer the longest clear span possible.

What do you guys think?

Can't help with the real figures. Your local building inspection depeartment can answer it though. If they say less than 16' you can suggest sandwiching 1/2 or 3/4 ply inbetween which will greatly increase the laod capacity. If you don't want that dep't involved, any architect should answer it without charging much if anything.

Harry K

 

[Carl_NH]

Depends on the type of pine. If its southern yellow pine (SYP) its denser and has a higher shear factor than eastern wihite pine (EWP) which has a lower shear factor.

When I designed and built the 24x36 barn the town/local building inspector wanted signed off prints from an engineering firm/architect. I used EWP for framing walls and sheathing the long side walls, but on both ends the engineering firm made us use 5/8" plywood for sheathing as they could not calculate the shear factor of 1" EWP on the end walls. Then for any load bearing joists or roof support it was standard lumber and floor joists.

Another good idea is as Harry K states above - laminate and glue and bolt 3/4" plywood on the 3x10s and it will support a lot more weight.

Sorta depends on your usage, if lightweight storage probably no problem. I would talk to an engineer or architect to see what they say as well.

 

[BHD]

if it is rough cut, consider it as 2 2x10" as modern lumber is only 1 1/2 thick

if not then see what a 2x10 is and or a 4x10 or double 2x10 and split the diffrnece say the 2x10 says 500lb and the 4x10 1000lb figure 750lb,

also caculate in the wood type,

but if you have to go throught an inspector, it does not matter what you think or the chart says, it is what he says,. so if you have to go thought an inspector of building departmetn, get his approval first, get it in writing,

again you need to set a load to work with, dead weight and live weight,

using this caculactor Maximum Span Calculator for Joists & Rafters

says at 15 foot 3 inches, I am sure the 3x10 would safely let you go 16 foot, span and that is 16 inches on center, dead load of 10 and live load of 40, (figured the lumber as (south pine fur),
this is as floor joist,

 

[kco]

I used to do such calculations for a living many, many years ago. But it's a complete mystery now and I'm sure others will respond with good answers. However, look up moment of inertia and bending moments for a rectangular beams (likely with a distributed load), and you'll have hours of entertainment.

As an approximation, I think you may be able to treat the two 3" x 10" similar to three 2" x 10" beams and use the span tables for a built-up beam using three 2" x 10" 's.

I'm sure others will correct me if this is wrong.

 

[quicksandfarmer]

I think of a "header" as a piece that goes over an opening in a bearing wall to carry and spread the load, so I'm having trouble picturing what you're doing. Sizing of a header depends upon the load on the bearing wall.

It sounds like you may be thinking of a beam to support floor joists. For that application there are two parameters, the span and the load. You calculate the load by figuring out how many square feet of floor the beam is supporting, and how many pounds per square feet that floor is rated for.

This table has 3x10 beams: http://www.awc.org/pdf/wsdd/c2b.pdf To use this table you need to know your species of wood, and it's bending strength (Fb). You can get bending strengths here: Maximum Span Calculator for Joists & Rafters

In beam applications, sistering doubles the bearing capacity for a given span.

Let me give you an example. Let's say you're using Eastern White Pine. The first table says it has a bending strength of 2156.25 psi. In the second table we'll use the column for 2000 psi, the rightmost column. The table doesn't go up to 16 feet (which might tell you something) but let's look at 12. On page 83 it has 12' span, and the fifth entry is 3x10. Reading all the way over to the right gives a capacity of 3961 lbs. If you are sistering two you can double that to 7922lbs. If your floor is built to hold 40 pounds/square foot that means you can support just under 200 square feet of floor. If the beam is between two walls the walls will hold half the load, so you can actually support 400 square feet with each 12' section of beam. Since the beam is 12' long that means just over 32', or 16' on each side of the beam.

That means the post at each end of each beam is carrying 8,000 lbs. Next step is to figure out what kind of post and footing you need to carry 8,000 lbs. Then what kind of joist system you need to span 16' at 40 lbs/sf.

You probably have to add some margin for error so you can't go all the way to 16', but you get the idea.

Around here you would have to use graded lumber with a stamp for that.

 

[cockeyedMFer]

Thanks Quicksand, you're right I meant beam, not header. The lumber is dimensional and graded, I believe #1 white pine, but I'll have to double check the grade stamp.

Where did you find 2156 psi for Fb of Eastern Pine? Several tables show either 1438 or 900 psi.

There's another chapter in your link that lists 13' and greater spans so I'll do some math and post the results later.

 

[BHD]

IF your in doubt bolt a steel flat inbetween them say a 3/16" by 8" or if there true 10" then go to 10" width,

 

[cockeyedMFer]

Here's a Sketchup design I drew up tonight for the proposed loft. The long beams with 45 degree braces are double 3x10x16. The beams that run perpendicular are triple 2x10x12 #1 graded pine. The joists are 2x10x8 #2 on 16" centers. Support posts are 6x6 PT.

Normally the joists would just tie into the main beam perpendicularly, but I'm trying to make use of lumber that's left over from other projects. The triple 2x10 beams and 8' joists are free, versus buying 2-2x12's and a bunch of 2x8x12's for example.

From my calculations and various span tables, everything is stronger than required except the 3x10 members, which are right on the line. It will probably have a 3/4 plywood strip laminated between the two beams to add to the safety factor, along with the 45 degree braces.

There's a 10'x54' loft on the opposite side of the barn that was built with triple 2x10 beams spanning 12', with 2x8 joists placed on top of the beam and ledger boards, rather hung off the beam and secured with hangers. Joist on top is cheaper and easier, but it makes a thick floor and my ancient forklift can barely reach the top. Plus it will give me about 7" more headroom upstairs.

The new loft is mainly for storing body parts, bulky boxed items, a Triumph TR3 in pieces and won't see large point loads like engines or pallet racking.

 

[quicksandfarmer]

Good drawings, that makes it a lot more clear. So the joists are holding the floor, the 12' beams are supporting the joists, the side poles and the 16' beams are holding the 12' beams, and the two new posts and one existing posts are holding the 16' beams.

The rule is when a beam is supported at two ends you assume each end takes half the load. So the three 12' beams in the middle are each holding up 1/4 of the floor and the two at the ends each have 1/8. The wall poles that support one end of the 12' beams will each take half of the load, so 1/16 for the end poles and 1/8 for the middle. For the 16' beams, only the load from the middle 12' beams is carried -- the rest goes directly onto the poles. So the load on the 16' beams is 1/8 of the floor. The middle new pole carries 1/4 of the floor and the end poles carry 1/8 each.

The total floor is 12 sheets of plywood or 384 SF. At 40 lbs/SF (pretty sturdy) that's 15,360 lbs for the whole thing. The load on each component is:

Middle 12' beams (1/4): 3840
End 12' beams (1/8):1920
Middle wall poles(1/8):1920
End wall poles(1/16): 960
16' beams(1/8):1920
Middle new pole(1/4): 3840
End new pole(1/8): 1920

That all looks pretty reasonable. I think you'll need some sort of footing for the new poles.