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enter image description hereI'm building a 1.5 story cabin and have a full perimeter 8" block foundation that's 20' x 40' with 16" x 16" piers inside...2 rows of 5ea piers. Piers are the same elevation as the perimeter block.

My joists will run with the 20' width, 3 joists to create the 20' span (sill plate to pier...pier to pier...pier to sill plate). Basically 3 joist 6.6' long. My questions are...

Can I run a sill plate from pier to pier the 40' way, for the girder (for lack of better definition) to sit on, and use that sill plate as a ledger for the joists? Didn't know if the ledger would have to be nailed to the sides of the girder.

Secondly, will I need to double or triple the girders.

I plan to use 2 x 8's for everything.

This is the way I had planned to frame it.

Here's a pic,

but the piers are actually 16" x 16" rather than 8" x 16".

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  • Why do you have a beam/ledger running the 40' direction on the piers? Do you have some load bearing wall riding above them? – CoAstroGeek Jan 13 '17 at 20:34
  • Just figured that was the easiest way to frame it. Nothing load bearing inside. Going to try to add a plan view pic showing the foundation only. – Snal Jan 13 '17 at 20:47
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No. Your joists must bear on the beam directly, using hangers or actually resting on it. Even if you'd bolt the ledger up to the bottom of the beam you'd be relying on cross-grain strength. Not a good situation.

As to your beam sizing question, that's for an engineer to answer (with drawings in hand). We don't have enough information about the structure as a whole to properly answer that. I can speculate, since 2x8 lumber isn't used for floor systems anymore, that even tripled you wouldn't meet most codes.

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  • How do joist hangers compare in strength to running the joists over the girder? Larry Haun put the joists over the girders here i.ytimg.com/vi/pQbKmPWCOf4/hqdefault.jpg – Jim Stewart Jan 14 '17 at 0:51
  • Full video of Larry Haun framing a floor youtube.com/watch?v=b2KfsJoZCnM – Jim Stewart Jan 14 '17 at 2:17
  • Specifically-designed hangers, such as those from Simpson, are commonly used in modern construction. However, they do make hangers of various thicknesses for different uses. You'd want the heavier ones. – isherwood Jan 14 '17 at 15:36
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Ok, I see what you're getting at.

You would have to have an engineer spec the beam (probably microlam) that runs on top of the piers, but then yes, you would use joist hangers to hang the joist from those beams.

For a 20' span, I think two rows of piers is overkill. You could easily go with a single row. Or even a clear span with something like a 12" TJI 360 or 14" TJI 110 (TJI Span Table). Till you figure the cost of those piers, beams, hangers, etc., I think you'll still come out ahead and have a better floor.

Note that the "sill plate" you show on top of the piers doesn't need to run between the pier - your joists will be supported by joist hangers from the beam.

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  • Thanks, but the piers are already in place. – Snal Jan 13 '17 at 21:37

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