[Bronson77]

Hi everyone,

I have a few questions about building a ~28x40 off-grid cabin. I've been studying foundation options and we want to go the sonotube pier and beam route.

- Does it make more sense to get the floor level by raising the sonotube concrete footings to achieve level or to attach a 6x6 or 8x8 in a bracket on the sonotube to achieve level for the beam/floor work?

Is there a certain number of sonotube piers I should be using for 28x40 dimensions?

In either of those situations, I'm not sure what to do once the concrete is established, especially on the corners of the foundation.

Let's assume the sonotubes dictate a level starting point, would I put brackets to hold (2) 2x6s for a beam? Is that strong enough or what is the standard? I would assume putting one beam at 0ft, 14ft, and 28ft would be the best option? Then nail single 2x6 boards at the ends tying the beams together?

Thanks for your help in advance.

 

[rjniles]

You need an engineer to design a foundation plan based on soil conditions and frost depths. This is not something you can wing


Sent from my Moto E (4) Plus using Tapatalk

 

[Bondo]

- Does it make more sense to get the floor level by raising the sonotube concrete footings to achieve level or to attach a 6x6 or 8x8 in a bracket on the sonotube to achieve level for the beam/floor work?

Ayuh,.... Level is established before ya dig,.....

That's why corner frames are put up, 'n string-lines are run, to measure off from,....

If necessary, different length tubes can be used to maintain level,....

Is there a certain number of sonotube piers I should be using for 28x40 dimensions?

A sonotube every 8' in every direction,.....

 

[Bronson77]

I mean building level, where the beam work starts. Not actual level level.

For instance, the first picture shows the sonotubes being level...

http://jjbventuresllc.com/images/0.jpg

The second picture shows the 6x6 posts being level, but not the sonotubes.

http://jjbventuresllc.com/images/1.jpg

Didn't know if it was better to use one method over the other?

 

[Nealtw]

With a foundation you my get away without and engineer, often just cheaper to over build.

When you go to post and beam you get into all kinds of stuff that is more critical than a foundation. Size of footing and steel required, size of tube and steel required.. Cross brasing and span of beams considereing live and dead loads of the building and other loads like snow and wind.

Then when you have all that figured out you have to consider wind under the structure as well as criters, are you back trying to figure out how to skirt the house with gound contact material and the chance that that could cause frost lift.

 

[Bronson77]

Then when you have all that figured out you have to consider wind under the structure as well as criters, are you back trying to figure out how to skirt the house with gound contact material and the chance that that could cause frost lift.

Yeah I was wondering how that is handled in colder climates. I'm sure insulating / heat tape pipes is required as well as using pex for incoming water since they are less likely to bust when freezing. I would also box the flooring with insulation and make sure it's tight to combat critters.

 

[de-nagorg]

I built a few off-grid cabins, in days gone by.

What we did was to use a transit, and sight everything to a level height, then build the floor on that.

You will need to be precise with your tube height, to insure that the floor is level, before the pour, and adding a strong-tie bracket in the fresh concrete, is the best way to anchor the cabin on it's piers.

And I would space the piers closer together than you proposed.

More like 5 rows of 4 piers each, to have them 7' apart in the 28' direction, and 8' apart in the 40' direction.

Using a double rim joist all the way around, a center double joist, and the cross ones as singles at 8' .


ED

 

[Bronson77]

I built a few off-grid cabins, in days gone by.

What we did was to use a transit, and sight everything to a level height, then build the floor on that.

You will need to be precise with your tube height, to insure that the floor is level, before the pour, and adding a strong-tie bracket in the fresh concrete, is the best way to anchor the cabin on it's piers.

And I would space the piers closer together than you proposed.

More like 5 rows of 4 piers each, to have them 7' apart in the 28' direction, and 8' apart in the 40' direction.

Using a double rim joist all the way around, a center double joist, and the cross ones as singles at 8' .


ED

ED - thank you! That's what I was looking for.

Any special treatment you need to consider for this type of foundation for cold weather like you have in Wyoming?

We'll be at 8000ft in Colorado. I mentioned earlier that I would box in the floor with insulation and heat tape/insulate pipes.

 

[Nealtw]

I built a few off-grid cabins, in days gone by.

What we did was to use a transit, and sight everything to a level height, then build the floor on that.

You will need to be precise with your tube height, to insure that the floor is level, before the pour, and adding a strong-tie bracket in the fresh concrete, is the best way to anchor the cabin on it's piers.

And I would space the piers closer together than you proposed.

More like 5 rows of 4 piers each, to have them 7' apart in the 28' direction, and 8' apart in the 40' direction.

Using a double rim joist all the way around, a center double joist, and the cross ones as singles at 8' .


ED

Ed, when have we ever disagreed?
Support in the center of the house is directly related to bearing walls above and there is nothing wrong with 2x10s 14 ft long and 2x12 16 ft long which also allows more insulation. Cost is easily off set with a the cost and labour of more piers. I do agree with smaller beams and shorter spans and slight variance in pier height and be spaced up to make level during construction. :biggrin2:

 

[de-nagorg]

We get nearly the same weather as northern Colorado, So, here Goes.

Set your piers back from the rim edge about 2 " to be able to use T1-11 siding as your skirt, around the perimeter to the ground, this will keep the wildlife out from under your cabin.

You will need to paint the T 1-11 every few years to keep it looking good.

Use 1/2" CDX plywood, as the underside of the joists to hold the insulation, and insulate the $#!^, out of the floor, then use standard T&G flooring as the floor.

Then you can build your cabin right on top of the floor.

We used a log kit, that had uniform 8" diameter logs, that stacked like "Lincoln Logs". using a 2" wide by 1/4" thick strip of foam insulation between each log, all the way up to the ridge beam.

Get all plumbing in before insulating and enclosing the floor, because tearing up your work later to plumb is wasteful.


ED

 

[Nealtw]

Beam on concrete pier.

 

[Bronson77]

We get nearly the same weather as northern Colorado, So, here Goes.

Set your piers back from the rim edge about 2 " to be able to use T1-11 siding as your skirt, around the perimeter to the ground, this will keep the wildlife out from under your cabin.

You will need to paint the T 1-11 every few years to keep it looking good.

Use 1/2" CDX plywood, as the underside of the joists to hold the insulation, and insulate the $#!^, out of the floor, then use standard T&G flooring as the floor.

Then you can build your cabin right on top of the floor.

We used a log kit, that had uniform 8" diameter logs, that stacked like "Lincoln Logs". using a 2" wide by 1/4" thick strip of foam insulation between each log, all the way up to the ridge beam.

Get all plumbing in before insulating and enclosing the floor, because tearing up your work later to plumb is wasteful.


ED

Ed, that's very helpful. When you say set back the pier from the edge, I'm not sure how to do that. I know why you say it, because you need the T1-11 to be flush against the outside edge of the board, but i'm unsure of how to get the pier underneath the outside boards unless the pier itself is a smaller diameter or the bracket is off center?

See the image below:

 

[Bronson77]

Beam on concrete pier.

Nice! Yeah that definitely helps me visualize what is going on. Thank you! As I mentioned to Ed in my last post, I'm not sure how to keep the pier from protruding the outside edge of the boards as to use T1-11 for siding without it hitting the pier. Any ideas?

 

[Nealtw]

Build your floor above the beams or hung from the beams. Build the exterior wall with 2x6s and bump them out an inch or two just like they do when the insulate the outside of a foundation.

 

[Bronson77]

Build your floor above the beams or hung from the beams. Build the exterior wall with 2x6s and bump them out an inch or two just like they do when the insulate the outside of a foundation.

Got it! I'm an idiot haha. I'm a newbie. Thanks for clarifying.

 

[Bronson77]

Would this be a good example of what you were explaining to me about building above the beams?

 

[Nealtw]

Would this be a good example of what you were explaining to me about building above the beams?

That is normal with decks where we keep them back a foot or two but with out an engineer there are better ways to cheat.

You can straight side a sono tub by adding a piece of plywood down to ground level

You build the floor with the rim on the edge of the beam and add another rim to the outside. Then if you kick the wall out a bit, you can get there.

 

[Bronson77]

What size diameter tube should I go with?

 

[Nealtw]

What size diameter tube should I go with?

the 64,000$ question and what size footing? :biggrin2:

 

[Bronson77]

I'm gonna draw up your recommendations in Sketchup and I'll post an image later so you can see. I really appreciate the help. You guys are an awesome resource.