Can I shim the top of an 6x6 post that i supporting a beam?


For a low-profile (but not ground level) deck, what's the shortest I can go with a notched 6x6 post? With an overall grade to deck surface height of 22", using a typical post and beam construction eats up my post height quickly when I factor in pier rising 2" above grade, a 1" post standoff, doubled 2x10 beam, 2x8 joist and 5/4 decking.

As such, I'm left with a measly 2.75" of post surface to support the beam. Seems like so little wood between fresh cuts is a recipe for disaster. Barely makes 6" clearance between beam and soil, too.

I suppose I could go without the cantilevered beam and go with a flush header (where beams and joists are flush at the top. Never did one of those, but it would seem the post centers would really need to be precise (no fudge factor).

Another thought I had was doing a beam to pier design, where the beams are strapped to the concrete pier tops (no post), but using larger lumber for the beams to get the height. No easy way to...

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Over my head

Sorry, I took a look at both of those links and I feel I am in over my head. I don't understand Modulus of Elasticity, etc.

Plus they are talking about joist spacing, but I'm having a hard time understanding how to correlate that to a single beam span across to end anchor points.

in the usplasticlumber table, I assume this is for plastic wood, so I'm not even sure the numbers should be used for tree wood...

for an example at 120F, they list a span for 100 psf Live Load. Does this mean 100 pounds per square foot, and if I want to have the 2x4 beam support 300 pounds in it's middle (again assuming that's the weakest point) I can only have a span of 25 inches? That's too short of a distance, and the 2x5 beam does not appear to be much better. I need to span a 10ft horizontal.

The other page with calculations confused me. Can you sugest other websites or search terms that I could use to try and find a method to calcualte this?...

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I'm in the concept phase of trying to come up with a design for a new 3 season porch to replace my existing open porch. One of the challenges I have is that I only have 17" of clearance between the ground and the exterior door to work with.

I'm still wrestling with using joists over beam versus inline beam. My current preference is joists over beam. Something like 2x6 joists over 2 2x10 beam or 2x8 joists over 2 2x8 beam. Still playing around with the layout/numbers.

My plan is to use the Simpson post connector and rest the beam in each one. I will have to be precise in getting the piers to be exactly level but I suspect that there will be some minor differences that I will need to shim out.

What are acceptable shims to use and where can I get them? My thought was that I would embed the j-bolt in the concrete and then shim the post base to get to the right height. I understand Simpson has those adjustable post-base that seems to rest on a single bolt but...

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Build upon a sturdy foundation.

A modified post and beam will work with pier, perimeter wall, and slab; even better is a pole foundation, where your posts are embedded deep in the ground (about 4'), and transfer the full weight of the building directly underground. This has great lateral stability.


Erect your posts; about 10' apart, in a grid. Use 6x6's - 4x4's are too flimsy, and almost instantly twist and split in the sun. If there happens to be an old structure you can build upon, simply remove all the rotten horizontal members and keep the treated posts. Remove and replace boards a few at a time so they remain up for bracing as you go.


Get your posts plumb. If you're putting them up new, brace them once they're plumb. If you're dealing with old posts, that have fallen out of plumb, use rope to straighten them. Attach the rope to the top of the post, with a nail nearby to keep the rope from slipping, and pull until it's plumb....

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For a large wood structure, like a deck, to stand up, it must be supported by a series of beams. These beams are connected to posts which hold the entire structure above the ground. While you can just nail these beams in at an angle, the stability of the entire structure rests on how well these beams are secured. To provide the maximum amount of support, the beams should be set into a recess that you create in the post.

Things you need

Measuring tape


Straight edge

Hand saw



1.2 cm (1/2 inch) drill bit

(2) 1.2 cm (1/2 inch) diameter, 15 cm (6 inch) long carriage bolts



Measure the width and depth of your beam.

Make a straight line parallel to the outside edge of your 15 by 15 cm (6 by 6 inch) "6-by-6" post. The line must be in from the edge a distance equal to the depth of your beam. It must also stretch down from the top of the post a distance equal to the...

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You are correct. The height of the pier was intentional too low and impresise. If I was precise in pouring my piers then I have poured them at the exact height so I could sit the beam directly on the pier and forget the post.

However the plan I followed indicated that getting the exact pier heights accross the entire deck to be at the perfect height is very difficult so it suggested using a short post and attaching the beam to the side of the post at the appropriate height to ensure everything is level, and then trimming the tops of the posts to be level with the beam.

The height of the pier is about 2" off the grade. The max height beam + pier + decking is 10" (lowest point). The joist would hang from the beam.

Sitting the beam directly on the pier would be okay if all my piers were at the correct height, but I'm willing to be they are +/- inch or two.

Perhaps using a shim is the best option is using a 4x4 shim and sitting the beam on the shims, as...

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I just put the beam in. It's 4x8, supported with 4x4's that are 6 feet apart (I should have probably made it 4 feet apart. It's purpose is to reinforce the floor in anticipation of an aquarium that will be placed between the beam and the foundation wall on the floor above. The joist span that the aquarium will sit on is 4 feet. ie; the main house beam is 10 or 11 feet from the wall. I added this beam 4 feet from the wall and the aquarium will sit above it between beam and wall.

I actually flipped the beam around and it was still "sagging". I thought ... oops, I have the crown side down, I'll flip it and ... same thing.

I'm thinking that the beam is not warped, and I'll check it with a laser level later, but get this...The beam spans about 6 joists or so. The first joist has a gap of 1/8", the second joist is almost above the post and it's snug up against the beam, the third joist gaps at 1/8", the fourth 1/4", the fifth is 1/8", the sixth is snug up and is...

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The most under-appreciated connection on a deck frame is probably the one between a post and the beam it supports. Although this joint may not get the respect it deserves, it is a critical load-path connection that needs to keep the post and beam aligned while properly transferring deck loads to the footing. A less obvious but equally important function is resisting uplift loads. And when a lateral force is applied to the post, the connection also has to resist beam rotation and post displacement.

Metal connectors are good at managing load paths and post displacement, but I haven't found any that are particularly effective at handling beam rotation. For that, I want a wood bridge between the beam and the post. Beam rotation isn't a problem with every post-to-beam connection, though, so I plan accordingly. The specific detail I use depends on the size of the post, the position of the beam, and whether the installation is for a new deck or a retrofit. In addition, I need to be...

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The Skinny on Shims

Dear Builder’s Engineer,

Ideally, pier/beam connections are always properly aligned, with the pier at the right elevation to fully support the beam above, but in the real world, a little shimming always seems to be required. Are shims sawn from framing lumber adequate for supporting beams? Plywood? Or are steel plates needed?

To answer this question we need to understand “compression perpendicular to grain”. The strength characteristics of wood vary depending on how it receives load. Doug Fir, for example, is good for about 1,000 psi in bending but only about 180 psi in shear. The type of stress a shim feels is neither bending nor shear, it is compression. But to make sure that everyone who designs with wood is thoroughly confused, there are two types of compression stresses: parallel to grain and perpendicular to grain.

Compression parallel to grain is the type of stress a post experiences. Load is applied to the top of the post and is...

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