Why Use Concrete Footing Blocks? || Dr Decks

Today we're going to talk about why some of us can use concrete footing blocks in very specific situations. And also how not all footing blocks are created equal.

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[futureteenidol]

The elevated post base in this video, the Simpson Strongtie EPB44PHDG, has some manufacturer installation requirements that greatly affect how you can use it with precast blocks. If you don't epoxy it into the block, it can only hold about 700 pounds as a point load. Unless you have a ton of pier blocks (like a post every 2 feet along a beam), your pier will probably need to support a lot more weight than that, even for a typical residential deck designed for a 50 pounds per square foot load across the whole deck. If you use the recommended epoxy to set the post base, it can hold over *3600* pounds. Though this is probably well beyond the crush limit of the typical concrete pier block, and also beyond the psf limit of most soils if you're using a 12x12" (1 square foot) block, it at least gets you past the tiny 700 pound limit. Epoxying the post base reveals another key limitation of the Simpson post base, though: you need at least 3" of concrete between the bottom of the hole and the bottom of the block (per manufacturer's instructions), and the rod has to be inserted at least 3.5" into the block. That's a total of 6.5" vertical, minimum. You may need more if you're elevating the post or beam less than 2.5" off of the block, as the rod on the base is 6" long. The round pier in this video looks like it's only about 6" high, as are all the round ones I've found in my area, which means there isn't enough concrete underneath the post base to get that rated 3600 pound weight capacity. In fact, the round piers available near me are drilled all the way through, with just a tiny dab of mortar to plug the hole at the bottom. Could you epoxy the post base into a 6" high pier anyway? Sure, but you'd need a structural engineer to calculate everything precisely to know how much weight it could hold. Furthermore, the diameters of the holes in precast piers vary dramatically. The round piers I've found don't even have a 3/4" diameter hole, which means you'd need to hammerdrill a larger hole to fit the Simpson post base. You need a 7/8" hole to epoxy the post base in, but you can go up to a 1" hole if you're not using epoxy. Always bring a post base, a tape measure, and a pencil to stick down the hole to see how deep it is when buying piers! Also, this post base is for a 4x4" nominal post only, not a 4x6" as he says in the video, though you can use it directly on the 4" face of a 4x6" beam. Just a final thing to keep in mind: the round pier on the left weighs close to 90 pounds, whereas the 12x12 on the right is probably only about 60 pounds or less. Unless you are a real beast, tossing around a 90 pound block is a lot harder than a 60 pounder, especially if you're putting it underneath an existing deck to improve vertical support. Just buy a few more 12x12 blocks and some extra brackets and save yourself some pain.

[fxxs]

Doode, this video is amazing. I've been trying to find a video that gives me useful introduction information on these footings and specially a tidbit about being in the cold, like Chicago. Great content, thank you!

[gBayCanada]

A good option is to use the standard 12 by 12 in block but to place one or two larger patio stones underneath them to distribute the load.

[dennislitvinov]

Hey Dr., could you please name the store where you buying these blocks? I am in Everett area and none of the basalite vendors carry those round blocks. Thanks

[zeropuckprep]

Almost every house in Hawaii is built on the regular 12” footing. They usually sit it on a 18” lump of cement which might increase its load bearing potential, but often the posts are sitting on the footing and not even attached.

[dr.timothyr.morris]

I want to support a 20' wide deck in Seattle . It currently has five 4x4 posts set onto 12x12" square pier blocks at the outer edge of the deck plus a row of 3 4x4 underneath. Each row of posts is holding up doubled 2x6-20' underneath where the 4x4 *divides* the 2x6es (one on each side of the 4x4 posts). There is a third 20' beam between the doubles that was being held up just by the rim joists. But the rim joists are all rotten and useless now. The 2x6 beams are *not* resting on top of the posts. Instead, the split 2x6's are secured horizontally with bolts and screws to the 4x4 posts.

The decking is a full surface of regular 2x4s with plywood ontop. So its a dry surface below. There is also a roof made of 2x6 on 20" spacing. Hilariously, The five outer posts holding up the roof are basically just resting on top of each other in **THREE** segments and toe nailed together. Super janky! There are ledger boards holding the roof and the deck to the house. This was all there when I bought the house 17 years ago and it wasn't in great shape then. Now there's been some sinking and there's a ton of rot on the outer edge. The outermost two 2x6, all the rim joists, and all the fascia all rotted through.

My plan is to to to attempt to preserve most of the deck wood by cutting the deck back 29" along the 20' edge to the next good (single) 2x6. Then I would set new posts to support it there and add a second 2x6 as the new outer rim joist. New 12' posts will support the deck and rebuilt roof in ONE piece. I'll also resupport the remaining (inner) doubled 2x6 with 3-5 posts new posts and supports.

1) First, Is this kind of horizontal fastening of two divided 2x6 to the 4x4 posts spaced 4' apart reasonable to do again? I'd like to preserve head height under the deck for storage. That plan seems to have held up fine for the last 25-30 years, so I'm hopeful. If not, what are better ways to run the beams?
2) In Seattle, how big of a post base should I pour? Are 10" wide Sono tubes reasonable ? 12"? Do I need to allow for a wide base below the tubes? How wide?
3) How deep should I set the post base depth to? You mentioned 12" below the surface? Shallow is nice, but should I go deeper?

[jessicahaines]

What about atlantic Canada. Ihave a large front step built. 3 years ago 8' × 12' we have those square footing holders and one is in my flower garden. Every time we come out the door its thud sinking that cement footing deeper. Help!

[matthewanacleto]

A link to those round blocks would be nice.

[victorlopez]

question - I'm not building a deck but planning to adding a lean behind my shed. It's ONLY 10 ' wide and the question I have is - Can I use these concrete deck blocks for my two post ? There won't be a LOT of weight at all other the the metal roofing which isn't heavy.

[NathanMellor]

I live in the Pacific Northwest, but don't know how to find the round ones.

[dyleppard]

Dear Dr. who sells these round footings? We are in SeaTac and cannot find them anywhere.

[tombrownca]

educational. thx from California, building a shed

[leejansen]

Okay, use the round ones. Got it. Now where do you find these "unicorns" in the PNW?

[rmtompkins]

I live near you in Olympia, WA. Where do I find your round blocks? Thanks

[detroyt]

Any of these work for a small deck with a light corrugated metal roof?

[VampO]

Can these be used for column supporting deck 10 ft up. Column goes through a lower deck. And concrete slab under. Or would you anchor to slab? I don’t feel like anchoring with an anchor is enough for a column.

[kennyg]

So is the purpose of a footing to distribute ground weight or only to secure a post to the ground?

[Objectra]

Hi. Quick question. According to building permit requirements in my area i am suppose to do 19" diam footing for intermediate posts, but i haven't seen tubes bigger than 16". What should i do?

[TeresaMiAmore]

Can these also be used to support 4 x 4 post for a freestanding carport and if so can regular cinder blocks be used as well? Thank you in advance

[christianleiva]

Thank you ! for the video. Question is normal to have those esquare concrete block under houses?