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Stokerace
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# Posted: 18 Dec 2024 06:14pm - Edited by: Stokerace
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Just started building a 28x28' bunkie / dining room as an addition to our summer cabin in NB Canada.
I am looking for tips on pier and beam construction. our adjacent 28x28 cabin is on pier and beam, built in the 50's and it's never caused any concern. In fact we like the easy crawl space for plumbing work and storage. The beams can be shimmed in minutes - if ever a change in level is seen (almost never).
These are being built by 3 tiers of 2 hollow concrete blocks per tier (8×8×16 each). Through the core of each will be vertical rebar hammered 2' into grade and 2' inside the pier. Then filled with concrete.
Here are my questions:
- filling each with concrete, but due to freezing temperatures it's going in as dry-mix. Will hydration / curing of the cement be effective in this context? (Sprinkled in by hose next April)
- I see lots of cabins around us with the whole structure sitting freely on peirs. So why is the internet full of videos showing people loading the piers/beams with carriage bolts and cemented in saddles? Benefit?? (The Alpes of Europe are full of antiquated log cabins sitting freely atop boulders.)
- Our four beams are 3 layers of 2x12 PT. I'm inclined to use simpson clips to firmly connect the joists. Am I right in thinking stiffness will be gained by basically joining the beams and joists?
Thanks for any tips or suggestions to improve this plan.
By the way if anyone is interested, sonotube piers have failed for some neighbors. Seems to be because the PSI of the pier is too much for the sand or, in other words, not enough surface area pushing down on the sand. Once the sonotube pier starts leaning too its game over. The permit options don't allow for any slab or basement so that's not part of the discussion here. The block pier idea was (ironically) suggested by a helical installer.
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rpe
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# Posted: 18 Dec 2024 08:29pm - Edited by: rpe
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Given you haven't had issues with your existing cabin, duplicating what worked there seems like a safe bet.
Do you have bedrock in your area? Up on the Canadian Shield, I have zero to about 6 ft of 'soil' with solid bedrock beneath. Water table (lake is 40 ft away) is about 3-5' below ground level depending on season. For our piers we always try to get down to bedrock, drill and pin with rebar, pour a 2'x2' pad on the bedrock, then on top thread pier blocks over the rebar, filling with premix and grouting joints as we go.
Q1 - I have no input on dry filling. I don't do this sort of work below freezing.
Q2 - Nearly every structure on my lake is sitting un-restrained on piers or bedrock as well. I questioned that at first, but the old timers said if a storm strong enough to move the structure came through, the 100+ ft pines around us would fall on the structure anyways. I'm not saying that's the right choice, but the logic does seem sound.
Q3 - You want to use the beams as part of the floor structure? Why not just frame a conventional floor sitting on top of the beams? That way you could keep your beams and piers slightly inside the footprint of the structure.
Interesting comments about the sonotubes. I replaced all the sonotube piers on our cabin with re-bar/concrete filled pier block piers as you describe. Many of the sonotube piers were cracked or leaning when we purchased the property. It's been 8 years now, and their replacements have been trouble-free. I attribute a big part of that success to the removal of silt/clay soil around the pier, and replacing with gravel/coarse sand. This dramatically reduces frost heave issues, as the coarse material doesn't wick moisture up into the frost zone repeatedly all winter like the clay does. Note that our water table is only a few feet below ground, so that concern may not apply in your location.
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ICC
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# Posted: 18 Dec 2024 08:30pm
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Quoting: Stokerace - filling each with concrete, but due to freezing temperatures it's going in as dry-mix.
I worry about getting just enough water into the mix. Too much water could wash the fine powdery portland cement out leaving a weak or no bond between sand, gravel and concrete block. I've dumped Sakrete in a hole along with a fence post and watered it, but the is just a fence post. No big disaster if it does not result in good concrete.
Quoting: Stokerace So why is the internet full of videos showing people loading the piers/beams with carriage bolts and cemented in saddles? Benefit?
Uplift resistance for high wind and seismic events?
Quoting: Stokerace Am I right in thinking stiffness will be gained by basically joining the beams and joists?
I like the H-1 clips for joists to beam connections. However, I don't see them providing any better stiffness iver toe-nailing. I like them for the exact positioning they make possible as well as providing excellent uplift resistance.
Sometimes when we see buildings that are hundreds of years old we are seeing the good ones, the ones that have received better maintenance than the ones that are now missing. They may also be l elements we can not see. An example I was shown in Switzerland years ago had a carved out bottom pocket in a timber that fitted over a lug or bump that was carved or cut aas a part of the large foundation rock; hidden once assembled. Many of the older buildings have more and heavier timbers locked together with joinery and pins and simply weigh more than stick framing.
Quoting: Stokerace By the way if anyone is interested, sonotube piers have failed for some neighbors
When Sonotubes, or other foundations fail it is often the fault of being unsuited for the conditions, as you point out. Commonly used wood piers can have the same issues. A properly sized concrete footer can eliminate such a failure from happening. Are there frost depth footers planned for the masonry block piers?
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Brettny
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# Posted: 18 Dec 2024 09:34pm
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Since it's an addition you need to do the same type of foundation as the original. Not frost protected. If they where different one would move in frost and ond wouldnt.
They do make solid 8x8x16 block and prety damn good concrete glue/epoxy. Can you wait until the spring to fill them?
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spencerin
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# Posted: 19 Dec 2024 08:45pm
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A1 - from what I've seen, dry-mix curing of concrete is a bad idea. I'd wait til it was warm enough to properly mix it.
A2 - I would agree that it's for resistance against any sort of force, whatever it may be.
A3 - Yes, rigidity would be gained by tying the beams and floor joists together.
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