Why Use Concrete Footing Blocks? || Dr Decks
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- Опубліковано 5 січ 2023
- 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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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!
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.
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.
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.
yep... Here on big Island it's the same. wonder if its due to having lava as ground and or no snow or and or frost?
Thank you ! for the video. Question is normal to have those esquare concrete block under houses?
A link to those round blocks would be nice.
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.
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
Question... I have some riding 4 x 6 deck posts The footers are buried below the frost line. I dug down and the concrete seems to be in pretty good shape however the 4 x 6 post has been embedded in the concrete. Is it okay to cut the Old Post flush with the concrete, auger out the old wood, drill rebar into the footer and pour over it using a sonotube?
I live near you in Olympia, WA. Where do I find your round blocks? Thanks
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?
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!
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
So is the purpose of a footing to distribute ground weight or only to secure a post to the ground?
Any of these work for a small deck with a light corrugated metal roof?
what if you put those unrecommended footings closer together, say maybe 4ft apart on a 12ft span, so using FOUR of them?
I live in the Pacific Northwest, but don't know how to find the round ones.
@NathanMellor @rmtompkins2221 As mentioned in the video, the manufacturer is Basalite. They are located in DuPont, WA
Okay, use the round ones. Got it. Now where do you find these "unicorns" in the PNW?
The circular block is not 18"x18" (324 sq."). Its footprint is circa 254 sq.", ( A = π r squared)
It’s 18” round
1.76 cf surface area, quite a bit more than the square block a 1 cf
Dear Dr. who sells these round footings? We are in SeaTac and cannot find them anywhere.
@dyleppard @leejansen5729 As mentioned in the video, the manufacturer is Basalite. They are located in DuPont, WA
you are doctor dink
Use these, but not these, but oh these are only available in Washington state. WTH!
small bolt for hundreds of potential pounds
I hate concrete. It is heavy and annoying and entirely unnecessary. I'm in the New Hampshire and have entirely switched to plastic footings with sunk posts (no the PT doesn't rot, I build fences too and posts don't rot unless there is organic material against it at ground level, so put some crushed stone there). I do the engineering then select the footing pad and posts size for the weight/soil I'm on. There are online calculators to help with this. The footing pad sits at the bottom of the hole (yeah, 4' minimum depth here) and the post sits on the pad. My first footing pad deck I ended up with a 16" pad with a 6x6 PT posts on it and a triple 2x beam sitting on that. Three posts, 24' wide deck. Looks great. Another HUGE benefit of sinking the posts is no racking. No need for any cross bracing or knee bracing. footingpad.com/ is the company I've been using.