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Small Cabin Forum / Member's Projects and Photos / 14x24 Workshop/Storage Shed Build
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rpe
Member
# Posted: 11 Sep 2020 17:07
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I'm building a workshop/storage shed combo at our property in northern Ontario. I thought I'd post up a few pictures. This set of four show the layout of the 8 support piers, two rows of four, 13' apart.
Layout
Layout
Bedrock
Bedrock
Sonotube
Sonotube
ScrewPile
ScrewPile


rpe
Member
# Posted: 11 Sep 2020 17:11 - Edited by: rpe
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In the layout image, the back row of piers are: 1.) surface bedrock, 2.) 30" depth to bedrock, 3.) 60" depth to bedrock, 4.) Boulders at 60" depth, no bedrock found.
The front row of piers are: 5.) 30" depth to bedrock, 6.) 72" no bedrock found, 7.) 72" no bedrock found, 8.) 60" boulders.

The sonotube piers were pinned via several pieces of rebar drilled and pounded into the rock at least 3" each. All excavation was backfilled with gravel rather than native soil which is hard grey clay for most of the depth.

rpe
Member
# Posted: 11 Sep 2020 17:15 - Edited by: rpe
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This is a picture of the screw piles that I used for some of the piers. The are just over 5 ft in length, and I used extensions to get above ground level. The pipes are 2-3/8" OD, 2" ID, hot dip galvanized, and the helix is 8" diameter. The ground was not suitable for actually screwing them in, but I set the bottoms in concrete below the frost line, and back-filled with gravel.
Picture 4 in the first post shows the extension pipes sticking up out of the holes as I was laying out the post locations.
_59.jpg
_59.jpg


rpe
Member
# Posted: 11 Sep 2020 17:17 - Edited by: rpe
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Here's where it sits now, with the floor framing complete, sitting on quadruple 2x8 pressure treated beams. On recommendation of some locals, I stuck a couple pieces of asphalt shingle between the pressure treated beam and each support. Rumour has it that extends beam life considerably.

Floor joists are rough-cut 2x8, so actual 2"x8". I had ordered a few extras, so I sistered the outer joists, and every third one throughout. Two rows of blocking were nailed in place as well. Joists were installed on 16" centers, but given all the sistering I did, I suppose 12" centers would have made more sense? Decking to go on is rough-cut 1x10.
WP_20200909_11_53_44.jpg
WP_20200909_11_53_44.jpg


Brettny
Member
# Posted: 12 Sep 2020 07:54
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What was your plan for screwing the screw piles in?

rpe
Member
# Posted: 12 Sep 2020 09:36
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The supplier of the screw piles loaned me a high-ratio gearbox powered by a mud mixing drill. Four foot handles supported by two willing helpers are supposed to steady unit, and resist the driving torque. I did give it a try briefly, but the gearbox was damaged from the previous job, so we ended up back to basics - shovel, breaker bar, and big shop vacuum. Based on the size of the hydraulic drive motors I saw mounted to their excavator equipment, I did have my doubts if this hand-held rig would work anyways, particularly in my soil.

I'm happy with how it all turned out, but will hold final endorsement until after a winter or two. Comparing my concrete/screw pile pier with the BigFoot and sonotube, or equivalent, there is far less concrete, and no rebar used. Also far less excavation required. Cost-wise, the screw piles were $80 each, and $20 for saddle to suit 6x6 beam. That, combined with say two bags of concrete mix ends up being $110 per pier. A BigFoot, and sonotube for that same 6-ft pier would be similar in material cost, with much more digging and mixing required.
One other benefit of these screw piles was the ease of trimming with a sawzall and metal cutting blade. I used a laser level to shoot a beam around the work-site, marked the posts, and cut them all to matching height.

Brettny
Member
# Posted: 12 Sep 2020 09:50
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Humm now you got me thinking. I have a hydraulic gear box attachment for my mini ex. Do local lumber yards have these things?

Brettny
Member
# Posted: 12 Sep 2020 09:59
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I did some quick numbers. 12inx48in sono tube with post base will cost me $45.

rpe
Member
# Posted: 12 Sep 2020 10:53
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4' x 10" sonotube: $8
Bigfoot: $29
Concrete: 8 bags @ $5.50
Rebar: 10ft $12

Totals $81 here in Ontario before taxes. Everything around here seems to be going up in price daily since Covid.

If I had a mini-ex accessible property, I'd probably just go with the Bigfoot (or preferably the 'Foottube'). However, given the week it took me to dig my smaller diameter pier holes by hand, I wouldn't want to have to repeat that with hole sizes to suit the BigFoot.

If you're in Ontario, here's the link to the guys I bought from. Even though their business is primarily installing the screw piles, they were quite willing to help out a 'diy-er' with advice, even to the point of loaning out tools no charge.

rpe
Member
# Posted: 12 Sep 2020 11:01
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Based on the pier work I did on my cottage a couple years back, I think multiple full-height rebar is important even with the BigFoot. The BigFoot itself should hold the pier down to prevent heaving upwards, but differential freezing could put huge side-loads on the sonotube portion of the pier. When I re-did the piers on my cottage several of the existing sonotube piers were cracked right through just below ground level. The rebar was holding the pieces in alignment so it would still carry the load come spring time. These could have easily collapsed completely without the rebar in place. Also, without rebar, the frost loading could easily snap that bigfoot section right off the rest of the pier, and then you're back to frost jacking again...
Here's a video of another BigFoot style product with integral rebar.

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