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Small Cabin Forum / Cabin Construction / Cabin foundation on bedrock help
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GSLaker
Member
# Posted: 22 Jan 2014 11:30am
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Hi folks,

I have a lease land title, and cannot pin to bedrock or pour concrete. If lease were to expire, cabin would have to be removed. Though very unlikely, it is a possibility.

So, thinking about building a cabin 16x24. I was going to use 8x8 timbers that are 16 feet long as the supports for my floor. The cabin will sit on bedrock, and I was going to run 5 of these 8x8 spaced at 6 feet. Once levelled, I would run 3 - 2x8 around the perimeter and 2 -2x8 nailed together at centre and sitting on the middle 8x8. I would then run 2x8x12 joist spaced at 12", using 2x8 hangers and tie into the centre doubled up 2x8. From there I would sheet the floor over with t/g 3/4" plywood.

The cabin would have a loft, measuring 16x12. The roof truss would be 2x10 with a centre beam of 3 - 2x10's extending through. And I was going to add a centre pole from the floor up to the beam at centre, for added support.

If anyone can share their thoughts, or if anyone has a similar cabin with pictures, I would certainly appreciate your help.

Thanks, Darren

Coastal
Member
# Posted: 22 Jan 2014 02:18pm
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I've built similar temporary buildings on treated 6x6 foundations, and they have really stood up well. Use the 6x6 as if they were concrete foundation walls, and frame up almost as normal from there.

Dekagoldwingers
Member
# Posted: 23 Jan 2014 11:33am
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I would consider building some kind of support under the 8x8's to use as levelling. That way water won't build up under or between the beams. Treated timber blocks would work. The 8x8's should be treated too, but if not, you can get some good stuff to apply to them before you stall.

Jim in NB
Member
# Posted: 23 Jan 2014 05:13pm
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I built my place 24x32 on 2x2 concrete pads - three rows of five pads and then used 3 2x6 posts leading up to three 2x10 beams. On top of this I built the floor joists with 2x8s. Has held up amazingly well with NO movement in over five years. Bedrock should be even better for you - but I would suggest you at least use pads similar to what I have - even if you have to take it out years from now not that big a job. And you cannot go wrong building from the a good foundation!
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SubArcticGuy
Member
# Posted: 23 Jan 2014 09:32pm
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Sounds like your plan is pretty beefy...I am building a 16x16 with a loft and I just have 2x6 floor joists and wooden cribbing holding it up.

Would GSLaker be Great Slave Laker? If so I would understand building a little more robust depending on how exposed you are to the lake. I am in a sheltered spot (south of the lake on a river system) so I don't have to worry about wind loads).

ChuckDynasty
Member
# Posted: 24 Jan 2014 07:08am
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Quoting: Jim in NB
I built my place 24x32 on 2x2 concrete pads

What is the thickness of your pads? Do they go below grade or sit on the surface? Thanks

OwenChristensen
Member
# Posted: 24 Jan 2014 07:43am
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Clean bedrock is the best foundation you can get.

Jim in NB
Member
# Posted: 25 Jan 2014 11:26am
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The pads are about 6" deep - used 2x6 for the forms - put in four pieces of rebar. I had a pad built and put them right on top of the pad. No issues with frost although the place is not heated in winter other than the odd weekend.

GSLaker
Member
# Posted: 7 Feb 2014 11:50pm
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Yes I'm building on Prosperous Lake. Are you around this area?

GSLaker
Member
# Posted: 7 Feb 2014 11:52pm
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Hey folks,

Thanks for the advice.

bldginsp
Member
# Posted: 8 Feb 2014 10:32am
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Since you can't pour concrete, I guess your only alternative is to stack rock for leveling, right? Even if you use pressure treated, I'd say the higher the better. One corner of the building will be closest to the bedrock, you need to decide how high up you want that corner. Log cabin builders say the sill logs should always be at least 18" above grade to avoid, or delay, rot, but that's not using pressure treated.

One thing people frequently neglect to do is dip the ends of pressure treated after they cut them. Then the ends rot where untreated wood is exposed. When possible, I try to cut the ends of pressure treated in advance, let them dry for months, then dip them for maximum absorbtion. Most pressure treated out of the lumber yard still has a high moisture content.

Tell us a little about the area there at Prosperous Lake. I see it is north of Yellowknife. Are there many cabins around the lake? Do people live there year round or is it strictly summer? How's the fishing?

SubArcticGuy
Member
# Posted: 8 Feb 2014 01:45pm
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I am south of the lake....east of the Slave River.

Fanman
Member
# Posted: 8 Feb 2014 08:12pm
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The original 18x18 part of my cabin (built around 1930) is built on 4x8 sill boards and interior crossbars, resting on an assortment of flat rocks and log sections, sitting on bedrock. It's no doubt been shimmed and jacked over the years (I had to do some major work six years ago when I got the place), but by and large it's held up well.

Modern pressure treated lumber would no doubt hold up even better.

When I built an addition a few years ago, I framed it out with (if memory serves) 2x8 or 2x10 PT sills, with an assortment of 2x6, 2x8, or 4x4 PT supports on the rock... cut to match the contour of the rock. In one case I chipped a flat spot on the rock to keep a support from sliding downhill. At one point I had to cut out a portion of a floor joist to go over a projecting rock, but mostly there's 1-2' of clearance between the joists and the rock (more like 4' in the front of the cabin).

GSLaker
Member
# Posted: 11 Feb 2014 09:11am
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Thanks for the advice. It's a beautiful lake. Not many cabins as there are many hoops to jump in order to secure a lease. As there are undoing land claims between the aboriginal people, Territorial government and federal government. There is a boat launch and the fishing is great. Lots of pike, whitefish, lake trout and the occasional pickerel. The lake is open June to The end of October, and then she freezes. Winter access is on the ice road via vehicle or snowmobile.

GSLaker
Member
# Posted: 11 Feb 2014 09:15am
Reply 


The area is mostly flat but I intend on building it up through concrete pads and treated 6x6. I'd like to get the 6x6 x12's up of and away from the bedrock by at least 18" and there is no issues with surface water, but when snow melts this will be the only concern with water.

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