|
Types
of Soils and Related Design Properties
(Most pwf's are designed on 2000 lbs soils).
|
Soil
Group
|
Unified
Soil Symbol
|
Soil
Description
|
Allowable
Bearing Sq. ft.
|
Drainage
Characteristics
|
Frost
Heave
Potential
|
Soil
Expansion
|
|
Group
1
Excellent
|
GS
|
Gravels,
gravel-sand no fines. |
3000 |
Good |
Low |
Low |
|
GP
|
Gravel-sand
no fines. |
3000 |
Good
|
Low |
Low |
|
SW
|
Sands,
gravelly sands with fines. |
2000 |
Good |
Low |
Low |
|
SP
|
Sands
gravelly sands with fines. |
2000 |
Good |
Low |
Low |
|
GM
|
Silty,
gravel, gravel-sand-silt. |
2000 |
Medium |
Medium |
Low |
|
SM
|
Silty
sand, sand-silt. |
2000 |
Medium |
Medium |
Low |
|
Group
2
Fair to Good
|
GC
|
Clayey
gravels, gravel-sand-clay |
2000 |
Medium |
Medium |
Low |
|
SC
|
Clayey
sands, sand-clay. |
2000 |
Medium |
Medium |
Low |
|
ML
|
Inorganic
silts, fine sand, clayey silts (l-p). |
1500 |
Medium |
High |
Low |
|
CL
|
Inorganic
clays, gravelly clays, sandy clay (m-p). |
1500 |
Medium |
Medium |
Medium |
Group
3
Poor |
CH |
Inorganic
clays of high plasticity, fat clays (h-p) |
1500 |
Poor |
Medium |
High |
| MH |
Inorganic
silts, fine sandy or silty soils, elastic silts. |
1500 |
Poor |
High |
High |
Group
4
Unsatisfactory |
OL |
Organic
silts, organic clays of low plasticity (l-p) Test
Soil. |
400 |
Poor |
Medium |
Medium |
|
OH
|
Organic
clays of medium to high plasticity (h-p) Test Soil. |
0 |
Unsatisfactory |
Medium |
High |
|
Pt
|
Peat
and other highly organic soils. (Test Soil). |
0 |
Unsatisfactory |
Medium |
High |
Allowable
bearing value shall be check in Group 4 soils.
Presumptive load bearing values of foundation materials.
(Michigan 2000 code).
Note: Clay soils work well for the permanent wood foundation
system.
Note:
Heavy soils will need a custom design.
Note:
Panel foundations can be site built or made in a
shop. When made so it cover up items that need inspection
by the Building Inspector. Third Party Inspection may
be required. (inspect for grade stamps, treatment stamps,
stud spacing, insulation, nailing, dip of saw cuts,
plywood requirments are some of the item that a third
party inspection will note.
All
Panel Wood Foundations must be designed and installed
in accordance with:
All current Building Codes Standards
While
wood foundations are easy to build, this is only true
if one is building from an accurate well designed plan.
When such a plan is incorrect, or if something is left
out of the plan or absent, or if a design is made using
a guide manual (these are not design manuals); major
mistakes can be made during the construction process.
These errors cause problems for the owner, builder,
and the building department.
Woodbasement.com a service of Permanent
Wood Foundation System (PWF), supported by Southern
Pine lumber users affiliated with the training and installation
of wood foundations.
.
.
|
Official Web
Site for the Permanent Wood Foundation System
