Another Foundation Question

[DaveOrr]

I am currently researching info prior to building my weekend get away cabin and I haven't found any info regarding the type of foundation and design needed for my location. We are located in Canadian shield country and my cabin location is exposed granite. My cabin location is 7 miles or so up the lake and inaccessible for pouring concrete and hand balming hundreds of concrete blocks and 80# sacks of concrete or cement mix is really out of the realm of feasibility.
I think my best bet is a pier and beam setup but I'm having difficulty figuring out the best way to go about it.
Should I
a: level out the areas that the piers will go with small pads pinned to the granite and use blocks to build it up
b: level and use timber saddles and 8"x8" PT posts
c: pin concrete filled sono tube columns to the rock

The lot slopes from the rear to the front of the cabin site by a few feet (won't know how much until the snow melts) and I am planning for a crawl space that is skirted to store stuff as well as house my fresh water system.

If I were to use the PT timbers I believe it would be fairly strong and resistant to shear as the areas between the piers would be 2"x4" framed construction sheathed with 3/8"-1/2" plywood.

Here's a look at the site from the lake
My plan is to build left of the tallish spruce just in front of the granite dome in the rear of the picture.



A closer look @ the location.



And a sat image. 



Any advice you could lend would surely be appreciated.   

[MountainDon]

So are you dealing with permafrost, or not?


I've been as far north as 62 degrees but only in summer.

[DaveOrr]

No permafrost in solid granite.
You need soil/peat/gravel etc in order to have any kind of frost issues.   

[MountainDon]

Sorry I should have re-read the OP.... granite was mentioned 

Which I think is good, better than permafrost at least.

If I were to use the PT timbers I believe it would be fairly strong and resistant to shear as the areas between the piers would be 2"x4" framed construction sheathed with 3/8"-1/2" plywood.

That is on the right track I believe, but the plywood should be 3/4 and PT as well as the framing being PT.  There is a foundation technique called PWF, permanent wood foundation. The plywood gives lateral strength to the  "box" the foundation is.  Just how to secure to the granite is the question needing an answer.

PWF 1

PWF 2

ED: fixed link 2

[DaveOrr]

Thanks for the info Don.
Reading through some of the other posts on foundations I came across these: https://www.permacolumn.com/sturdi-wall-sw66
This would mean using 6x6's though. They do make single L's and I could use 2 to do the same thing with an 8x8.

[DaveOrr]

Forgot to add that PT framing and plywood is a given.

[hpinson]

Is that near the Rae Lakes? 

I'm curious what is the best practice for similar structure foundations in the area? As I remember that granite outcropping is all over the place around Yellowknife, and many small houses are built on it.  What are others doing?

[UK4X4]

Granite- pain in the rear to drill- you'd need a descent full rotary hammer SDS drill

Then either use expanding bolts or resin in all thread- rebar depending on what type of pier you'd be planning on

This type of drill- multiple bits

http://www.bosch-professional.com/gb/en/gbh-3-28-dfr-16877-ocs-p/


Use putty or plasticine and mold a circular donut- fill with water to keep the bit cool

add a friend with a plant sprayer to re-fill while drilling

Takes a while but will give you a solid connection to the rock.

if your planning rebar into a concrete footing then drill the holes at an angle to assist with uplift.

I think I'd set all thread- use some sonotube to make a level pad- then bolt in your posts to the allthread

really depends on what the level diferences will be across the build - room for bracing - or if low then rebar and just sonotubes or blocks

[Squirl]

I second Don.  PWF is the lightest and fastest for that location.  If you can get the wood in for the cabin, you can get the wood in for the foundation.  No hauling concrete.  If you are in granite and not clay drainage shouldn't be an issue.  With the cold weather most of the year, it should last lifetimes.  In addition to the PWF guides, there are specs for design built into the ICC.
http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_4_par082.htm
If you aren't familiar with it or have any questions, just ask away.

If you used 2x6 PWF timbers spaced 16" O/C and 19/32 or 15/32 PWF plywood you could skip the 8x8 timbers. 

[Squirl]

Also with the PWF, you skip those beefed up timbers for the girders on a pier and beam, and can just start building the floor.

[DaveOrr]

I second Don.  PWF is the lightest and fastest for that location.  If you can get the wood in for the cabin, you can get the wood in for the foundation.  No hauling concrete.  If you are in granite and not clay drainage shouldn't be an issue.  With the cold weather most of the year, it should last lifetimes.  In addition to the PWF guides, there are specs for design built into the ICC.
http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_4_par082.htm
If you aren't familiar with it or have any questions, just ask away.

If you used 2x6 PWF timbers spaced 16" O/C and 19/32 or 15/32 PWF plywood you could skip the 8x8 timbers.

Good points.
I had thought about dropping the 8x8's and using 2x6 framing on grade and all thread to lag it down.
I'm going to have to rent a drill as my little 1/2" hammer drill is not up to the task.
I will know more when the snow is gone. I'm not sure what the rock looks like underneath the snow.   
Hopefully it's smooth and not broken as it will make things a lot easier.

Most people just use blocking placed on the ground for a foundation and I could do that but I want the crawl space storage under the cabin. I want to store my cabin building lumber in there while building (things tend to walk otherwise) and I want to put my domestic water system in there as well as store various cabin stuff (fuel cans, tools etc).

Wood, even untreated wood lasts a very long time up here. Might have something to do with stuff being frozen for 7 months of the year. 

[DaveOrr]

Is that near the Rae Lakes? 

I'm curious what is the best practice for similar structure foundations in the area? As I remember that granite outcropping is all over the place around Yellowknife, and many small houses are built on it.  What are others doing?

About 60 miles up the highway.   

[JRR]

Does the area have stones that can be stacked by hand?

[DaveOrr]

Does the area have stones that can be stacked by hand?

Nope, it's all solid granite.
4 billion year old Canadian Shield rock.