Standoff Post Base, 4x4 to 12x12 Posts

The 1" standoff

The post doesn't sit on the concrete. It stands on two 1" square steel tubes welded across the pocket, which keep its end grain 1" off the slab so water can drain away and the wood can dry. A drain cutout at the bottom of each side plate lets water out from under the post. Don't seal around the base; the drain cutouts need to stay open. End grain that sits wet on concrete is where posts rot.

The International Residential Code's rules on protecting wood from decay (section R317) are why builders look for a 1" standoff. Whether your post needs one, and what else it needs, is for your local code and building official to say.

Sizes this post base is made in

• Post width: 3" to 12". This is the gap between the two side plates.
• Base width: 5" to 15". This is how wide each side plate is on the post's face.
• Base height: 7 1/2" to 12".
• Post bolts: 3/16" to 1".
• Anchor: 1/2" to 1". The configurator calls it the base fastener.

It fits 4x4 to 12x12 posts, and the pocket is 1/16" wider than the post you enter, so the post slides in. Sizes are set to the 1/8". The configurator opens on a 6" post in a base 8" wide and 8" tall, with 5/8" bolts and a 5/8" anchor.

Bolt holes and the height rule

Each side plate has one column of bolt holes down its center. The top hole is 1 1/2" below the plate's top edge, and the next is 3" under it. A base over 10" tall gets a third. The bottom plate has a single anchor hole in the middle.

The post's bottom end sits 1" above the bottom plate, on the standoffs. The configurator keeps the lowest post bolt at least 3 1/2 bolt diameters above that end, because a bolt too near end grain can split the post. In practice, a 5/8" bolt needs a base at least 7 3/4" tall. A 1" bolt needs a base 9" to 10" tall, or the full 12". Just past 10", the third hole lands lower on the post, so the configurator may ask for a taller base or a smaller bolt. Our guide has more on end distance.

Anchoring it

The base takes one anchor, from 1/2" to 1". In a new slab or footing that is usually an anchor bolt cast into the concrete. In existing concrete it is usually a threaded rod set with anchoring adhesive (epoxy). The anchor's type, size, depth, and distance from the concrete's edge are for the anchor maker's instructions and your engineer.

What a post base doesn't do

A post base holds the bottom of a post in place. It doesn't keep the post from leaning. A post that stands alone, like a fence post or the post of a carport or pergola with no bracing, needs to be braced some other way. Ask an engineer.

Questions

Will it fit a rough-sawn 8x8 or 10x10?

Yes. It's made to the width you enter, up to 12", so a rough-sawn post gets a pocket made for its real size.

What connects the top of the post?

A post cap seats a beam on the post. There are also caps for corners and for crossing beams.

What if my post is wider than 12"?

Tell us its size through the quote form. Bases outside the configurator's range are made to order from your numbers or your plans.

The basics

• 3/16" A36 steel plate, laser cut and welded in our ISO 9001 shop in Texas.
• Holes are cut 1/16" larger than the fastener you choose. Fasteners aren't included.
• Enter your timber's real size, not its name. How to measure a timber.
• Bare steel, or matte black powder coat added in the cart.
• Ships free in the lower 48 states.
• No published load ratings. Ask your engineer, and see what to give them.