Foundation and Type II Soil

[bill2]

I am going to build a log cabin, 1.5 stories, 32'x34'. I am almost certain that the soil is Type II. Does anyone know what type of foundation design I should use? I was going to use a regular strip foundation on the perimeter and 4 piers in the middle. Location is West Central Virginia and the frost depth is 18". I planned on 3 lengths of rebar tied together in the strip and 4 at right angles in the pad for the piers. However, it is mystifying to me what compaction you need to do and how deep under the strip and the piers. Do you use the soil you excavated or bring in gravel and sand or what? Any advice would be appreciated.      

[Redoverfarm]

Hi Bill2. What area of VA are you located?  Doesn't sound like you will be far from me.  What type of logs are you going to use.  Manufactured or reclaimed logs? 

Here is a pretty good article on what you are going to do.

http://www.diydoctor.org.uk/projects/foundation%20project.htm

[bill2]

Hi Redoverfarm, thanks for the link. The logs are manufactured white pine 6x8 square although I might have to go to 8x8. That is another question I have about R Values because as I read the code (2003 IRC) I don't see how you can pass but maybe there is an exception in old Virginny.

[Redoverfarm]

Bill if you are buying the logs as part of a kit home then the manufacturer should be able to provided you with the in's & out's of code reference to their material.  If you are planning on cutting your own then a visit to a manufacturer to find out what you need and proceed from their.  Their are several companies that build in your area.  Appalachain, Jim Barna and North Eastern arejust a few that come to mind. 

Mine are the original hand hewed built on a standard crawlspace and half basement with a bumpout to the rear.  You can view it at the links on the signature line.

[MountainDon]

The logs are manufactured white pine 6x8 square although I might have to go to 8x8. That is another question I have about R Values because as I read the code (2003 IRC) I don't see how you can pass but maybe there is an exception in old Virginny.

As far as the energy code compliance goes, follow the link below to ResChek. ResChek not only works with conventional wood stick construction but the last couple versions works with Logs, metal, masonry, ICF and SIP's. Virginia is one of the states that uses it to determine energy code compliance.

http://www.energycodes.gov/implement/state_codes/index.stm

For the structure itself, have you asked what building code you have to comply with? There's a newer code, IRC2006 that may be applicable.

[Don_P]

hi bill2,
I'm a carpenter down in Grayson County. MountainDon is right in that ResCheck can be used to figure your log home. Many suppliers can handle that if not the building dept can probably refer you to someone who can do the rescheck calcs.

We are using the '06 IRC, this is a link to an online version;
https://www2.iccsafe.org/states/Virginia/Residential/Res-Frameset.html

Foundations most of the time are simply excavated, in this case to 18" below finished grade, the footings are then poured on undisturbed soil. Typically there is no compaction, if you hit unusual or weak soil then you need to get a geotech engineer (or don't build there.)On top of that lay up block, I like to get the logs a couple of feet above grade. to get them out of the soil splash zone. Also, forget decks, either put on a roofed porch or do a ground level patio, splash right at log level is not a good thing.

There is a new log code that we have not adopted in the state yet but I imagine most inspectors would respect. At 8" thick you begin to get into the mass effect of the logs in addition to their insulative properties.

[diyfrank]

Hi Bill, I'm not sure what Type 2 soil is.We go by class a, class b, class c
If type 2 is the same as class b then thats what most foundations get pored on. Class a is bed rock , hard pan. sand / gravel that has never been disturbed. and lacks the presents of water. Class c is crap and can be all the above when water is present.
Compaction is for placed fill.  Native ground, you'll strip off the top soil and anything containing organics.  wood, grass etc.
you go down till you reach your desired depth. If it too far out of level you can step your footings. You should aways probe the excavated ground to verify it's suitable. You can use a short length of rebar and press down  hard on the grade. If you go down an inch or two you should be fine.  Sometimes you can push it down a foot or two. Thats alright if your in sand but otherwise dig down past the soft spots.  You can fill it back in with rock and compact it to bring it up to the desired grade. I wouldn't use the excavated soil in any place where compaction is necessary unless you know it will go in tight and have the equipment to compact. Having a geotech look at your soil is a good idea if you plan on building on top of any placed fill. 

[Don_P]

If you go to table 405.1 in chapter 4 of the codebook linked above it describes Type II soils.
At the beginning of that chapter is a table (R401.4.1) of presumed load bearing strengths for various soil types.

Also notice R602.1.3 now specifically adresses logs, they must be graded.

[diyfrank]

A-ha a chart..
Sounds like Group 2 and Class b is about the same soil classification. It look fine for foundations except the ML list high frost heave potential.