Notch in 6x6 post

[midrover170]

Hi folks -

In a couple weeks i'll be setting my 6x6 posts for my post/pier foundation. I'm planning to set them on Simpson ABU66Z's. For the beam, I'm sistering two 2x12's and setting them in a post notch.

Here's the question: Is there a minimum height I need between the lower portion of the notch and the base of the post? The ABU66Z's are about 6 inches tall anyhow, so is that a good distance for a minimum? I'll be attaching the post base to the post with two carriage bolts. I don't want my cabin really high off the ground, so the closer the bottom of the notch is to the bottom of the post, the lower in height I'll be. The goal is a 24"-30" high space under the cabin, nothing more than that. 

I guess an "extreme" alternative is to cut the notch really low and carriage bolt from the post base through the post AND the notch/beam... that seems kind of sketchy though and probably wouldn't leave me with enough room to crawl around.

Hopefully that made sense. Trying to avoid any  moments.

BTW, made a water level following some Youtube videos over the weekend. What a cool device that is. Can't wait to use it in the field.

-D

[John Raabe]

I would add a couple of inches above the bracket for the start of the notch cut. Can't really justify that choice but it could provide a nailing area that might prove helpful.

[MountainDon]

I look at the minimum  as being derived from the minimum amount of clearance I want under the beams and floor joists.

The first part of that is for whether or not PT wood is required. For beams if the distance from ground to bottom of beam is less than 12 inches, the beam should be PT. For floor joists if the distance from ground to bottom of joist is less than 18" the joists should be PT.

The second part is are you comfortable with having to crawl under a beam with 12 inch clearance or joists with 18 inch clearance  if  when that becomes necessary.



Then there is the question of how that short post is going to be attached to the beams and joists? Where the post top meets the beam is a potential hinge or pivot point. The ABU bases also have a potential hinge or pivot point at the lower end. That could be a double whammy in the event of an earthquake.

Shorter is better on the one hand but that make other things more difficult.   

[midrover170]

Thanks John and Don -

Don, you got me thinking. I thought all along I'd need to use PT for my beams and joists, just due to the nature of post/pier builds. If I meet those minimum thresholds, and don't have to use PT lumber, that would be a big cost saver.

I whipped up the drawing below. If I did something like that (obviously with a beam in the notch), I could avoid PT lumber? Finished grade would be at the bottom of the pier. Let me know when you get a chance. That's an exciting prospect.

[Don_P]

Yes, MtDon is correct on PT and clearances to grade.

Finished grade would be at the bottom of the pier.

But do understand the pier extends down to a spread footing who's bottom is at frost depth.

To make a 3" notch it sure helps to have an 8" skillsaw. If that notched post extends up to the top plate of the wall, the sheathed wall is then bracing the post at the point of rotation at the beam that MtDon mentioned.

[midrover170]

Thanks, DonP. That's great news. I may still go with PT for my beams due to the strength of Southern Pine. Beats the Doug Fir based on my research. It's hard to find Southern Pine around here unless it's PT.

But do understand the pier extends down to a spread footing who's bottom is at frost depth.

Trust me. I FULLY understand how far down those suckers go. I just mixed a 140 bags of Quikrete getting them in place  . Here's a more detailed drawing of what i'm planning. I was thinking of using hurricane ties for the joist/beam connections. That normal? It may be tight crawling under the beam this way, but I could always access the "crawlspace" from the ends of the cabin where the beam doesn't run across. 

[Don_P]

Actually SYP was derated a couple of years ago, it now has design strength values about equal to SPF, I've been getting #1 SYP to get good numbers but dougfir in #2 is now the better strength material. The span calc at awc.org gives design values at the bottom of its' results. Nothing treats better than SYP though.

Taking care of another hinge point, a poorly braced girder to joist. If you use a double 2x12 girder and 2x8 joists, a 2x4 ledger will insert under the joists. No hangers or hurricane ties needed, nail the first 2x12 into notch then end nail the 2x8 joists, then apply the second 2x12, then the ledger pulled or clamped up snug and well nailed. Notice I drew the full height 6x6...locking up those points of rotation.

[John Raabe]

Nice solid detail Don. Provides better access to the crawlspace and, if post and beam are flush, the wall sheathing can carry down continuous to the bottom of the beam and be nailed off to add considerable racking resistance.

[midrover170]

Thanks, everyone. Always super helpful getting your feedback.

Unfortunately, I don't think I'll be able to use DonP's design because my piers are already poured and I was planning on small (1 ft.) cantilevers. See below:





I guess I'll have to stick to hurricane ties, and  crossbracing of the posts?