Concrete Piers on sloped lot - help

[cabin fever]

Hi guys, I am about to start digging my piers but thought I would post up here for a little reassurance before I get started.

Here is what I am building - right to the point:

-12'x14' 1.5 story bunkie
-10" concrete piers burred 4 ft. with 4x15m bars in each
-3 rows of piers (4 piers per row)
-6x6 P.T. posts on top of piers
-3 layer 2x10" girders (x3)
-2x8 joists (box framed)
-10' 2x6 stud walls
-balloon framed loft / 2nd floor
-12/12 tin roof
-2x10 rafters
-3"x16" glulam ridge beam


The slope is what worries me.  The angle finder is saying 20 degrees or about 1:5 slope (1 vertical to 5 horizontal).  The test hole I dug revealed 1-2 ft peat with a dense sand below with large cobbles everywhere (I couldnt get below 4.5 ft with a post hole digger).  All posts will have cross bracing where ever possible.

The question is:
-is a 10" reinforced sono tube buried 4-5 feet sufficient?  This will all be dug by hand as I'm in a remote spot, so going any deeper or increasing to 12" tubes will be difficult.  Record frost in the area penetrated 5 feet... I am also in a snow belt, not uncommon to see 5 feet of snow on the ground or 60PSF snow loads, but the 12/12 metal roof will help with this.

-what is best orientation - eg.  Should I run the Girders parallel or perpendicular to the slope (girders run the 14ft length)?  - But also consider the ridge beam will put most of the weight to the gable sides

[Urokidd]

I am doing a 20x32 and doing piers on a sloped lot also (@ 15 degrees).

I decided against just doing Sonotubes and instead will do the 24" plastic footing with a Sonotube @ 5ft. That will give me greater load capacity, prevent or reduce the frost heave and allows me to carry weight out to a deck (further out on the slope) where I can have storage underneath for the kayaks etc.

I'm not sure that you need a Glulam for that size building a 2x10x16 would be more than sufficient.

As for the positioning of the bunkie  I will have my gable ends facing west and east so I can take advantage of some solar and PV panels on the roof which will be facing south.

Post some photos, we all like to see whats going on! Good luck

[cabin fever]

After spending a few days up there laying out the construction lines ect... We decided it was a bad idea to build on the slope.  From the highest to lowest point was about 7 feet over the 14 foot run... Turns out it was a 2:1 slope.   This just creates too much work for everyone, especially since most of my helpers work for beer and boat rides.  Just thinking about mixing and pouring the concrete by hand, working from a ladder 99% of the time, make my stomach turn.

I decided to use up one of the only flat spots with a view of the lake instead, this will make things easier but I will have to re locate the fire pit / drinking area.


thanks for the suggestions Urokidd and good luck with your build, 15 degree slope is much more dooable