Sills, solid vs laminate

[Arky217]

Soon to start CSMilling some Southern Yellow Pine for foundation sills.
They will be 6"x8"x12' on 6' span piers.
What would be the upside/downside of using 6"x8"s solid cants versus nailing together (3) 2"x8" or (4) 1.5"x8" pieces ?

Thanks,
Arky

 

[woodshop]

Soon to start CSMilling some Southern Yellow Pine for foundation sills.
They will be 6"x8"x12' on 6' span piers.
What would be the upside/downside of using 6"x8"s solid cants versus nailing together (3) 2"x8" or (4) 1.5"x8" pieces ?

Thanks,
Arky

I'm not a building structural engineer, but from things I have read, in general nailed or sistered boards together are not quite as strong as solid beams. How much less strong? I don't know. I suspect that if you plane the boards dead flat and then glue/screw them correctly, there would be little difference. But wait for somebody that knows what they are talking about before you make your decision.

 

[carvinmark]

I'm not a building structural engineer, but from things I have read, in general nailed or sistered boards together are not quite as strong as solid beams. How much less strong? I don't know. I suspect that if you plane the boards dead flat and then glue/screw them correctly, there would be little difference. But wait for somebody that knows what they are talking about before you make your decision.

+1, might be some shrinkage with solid beams???????opcorn:

 

[Trigger-Time]

Think it would depend allot on how the grain of the 2X8's run.
Also what grade of lumber #3, #1 or DSS. Years ago I worked
in a roof truss factory, that Southern Yellow Pine is some
Hard and stout stuff for pine. When nailing close to the ends
I would drill pilot holes to keep it from splitting.


Gary

 

[Sawyer Rob]

Soon to start CSMilling some Southern Yellow Pine for foundation sills.
They will be 6"x8"x12' on 6' span piers.
What would be the upside/downside of using 6"x8"s solid cants versus nailing together (3) 2"x8" or (4) 1.5"x8" pieces ?

Thanks,
Arky

If you glue/screw/nail 3/4" plywood between the 2x8's, it ADD'S unbelivable strength to the beam... It will be MUCH stronger than a solid cant.

Rob

 

[Arky217]

Well, if I make the sills (or beams if you prefer) one piece, they would be pith-centered from the logs to minimize warping. Either way the sills would be sticker stacked to air dry until I have finished milling all of the framing lumber. (This is for a 26x48 dwelling)

If solid 6x8, one advantage would be less milling, but they might not be completely air dried by the time I'm ready for them.

If planks, they probably would be down around 20% mc, and easier to handle, but would require more milling and the effort to fasten them together.

As far as strength, I've heard it both ways. I've heard several say that the solid piece would be stronger, but according to the span program that I use (an Excel spreadsheet program called powerspantablelite.xls), the planks would be much stronger. For example, the program shows that a beam spanning 6' supporting 12' joists on both sides with a live load of 40psf and a dead load of 10psf, a 5.5"x7.5" beam would have a bending overdesign of 17% whereas just (3) 1.5"x7.5" planks together (total 4.5" width instead of 5.5") would have a bending overdesign of 49%. (And that's just side by side, not glued or even nailed together, go figure ?)

Anyway, I'm leaning toward the solid sills, mainly because of quite a bit less chainsaw milling.
Anyone think this might be a major mistake ?

Thanks,
Arky

 

[Sawyer Rob]

Well, if I make the sills (or beams if you prefer) one piece, they would be pith-centered from the logs to minimize warping. Either way the sills would be sticker stacked to air dry until I have finished milling all of the framing lumber. (This is for a 26x48 dwelling)

If solid 6x8, one advantage would be less milling, but they might not be completely air dried by the time I'm ready for them.

If planks, they probably would be down around 20% mc, and easier to handle, but would require more milling and the effort to fasten them together.

As far as strength, I've heard it both ways. I've heard several say that the solid piece would be stronger, but according to the span program that I use (an Excel spreadsheet program called powerspantablelite.xls), the planks would be much stronger. For example, the program shows that a beam spanning 6' supporting 12' joists on both sides with a live load of 40psf and a dead load of 10psf, a 5.5"x7.5" beam would have a bending overdesign of 17% whereas just (3) 1.5"x7.5" planks together (total 4.5" width instead of 5.5") would have a bending overdesign of 49%. (And that's just side by side, not glued or even nailed together, go figure ?)

Anyway, I'm leaning toward the solid sills, mainly because of quite a bit less chainsaw milling.
Anyone think this might be a major mistake ?

Thanks,
Arky

I wouldn't expect them to dry straight... That's another advantage of glueing some up to make the beam. If you need them deadnuts on, saw them over size now, and resaw them just before using them... This only takes is a few minutes with a bandmill, and they come out really nice...

I'm with the "glued up" crowd, as for what one will be stronger.

Rob

 

[clearance]

Sills have only compression on them, 2x4s are used as sill plates on many houses. Solid will be no problem, if you do as Sawyer Rob suggests.