Troubleshooting Panel Wood Foundations

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This checklist can be used for troubleshooting a problem foundation inpart with a third party inspection.
Third Party Inspection can be done with this checklist yourself, or by a designer of wood foundation.
This checklist may help you with your foundation problem.

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.

Troubleshooting
Made simple with out a design

A.      At the Bottom of the Foundation Wall

Water or moisture on the top of Bottom Wall Plate and/or high humidity in the basement

Causes:

a. No Sump.

b. No or too little gravel under the floor or under the footing plate or floor.

c. There is something damming the water under the floor or under the footing plate.                

d. The Vapor Barrier has been extended under the footing plate.

e. The Vapor Barrier has not been cut off at the bottom of the footing plate, but is instead extended into the gravel.                 

f.  The Vapor Barrier has been left off the Wall or omitted under the floor.

g. The bottom of the sump has not been perforated or open to the gravel.

h. The sump is not drained to a positive drain (by gravity or pump).

i.  The sump is not surrounded with at least 4 inches of gravel.                               

Foundation wall sinks out of level at any point along the foundation wall.

Causes:

a.   The axial load is too heavy for the size of the footing plate.

b.   There is not enough gravel depth or width under the footing plate.

c. There is too much building weight for the gravel depth under the footing plate (gravel shear).
 note this can happen only with undersize footing plates.

d.       The footing plate is too wide giving rise too induced tension. (oversize footing plates)

e.       Plywood stiffener is too thin.

f.         Plywood stiffener face grain is not perpendicular to footing plate grain.

g.       Plywood or concrete concentrated load pad is missing or too small for the point load.

h.       The load pad is not thick enough for the concentrated load.

i.         If a plywood pad, the adjacent pieces are not perpendicular to each other.

j.         If a plywood pad, the adjacent pieces are not glued together.

k.       The footing plate is plywood, the adjacent pieces are not perpendicular only when required,
 are not enough layers thick, are too wide, or are not glued together as required by some 
 designs.                

The foundation wall is bowed, out of plumb, or deflecting inward.

Causes:

a. There is not enough bearing against the floor by the bottom edge of the studs.

b. The grade for the species used for studs is too low.

c. The spacing of the studs is too great.

d. Insufficient number and/or size and diameter of nails used to nail bottom top plate to studs.

e. The grade for the species used for top plates are too low.

f.  Nail spacing is too far apart and/or size and diameter of nails used to nail the two top plates
together.

g.       Nail spacing is too far apart and/or size and diameter of nails used to nail band joists to top
plates.

h.       Floor joists not adequately attached to the band and the top plates (this may be done with pwf
 framing straps, joist angles, or joist hangers---The number of nails, size, and diameter is
significant for each type of framing anchor).

 i.         Shear wall(s) may be needed.

 j.         The length of the shear wall(s) may be too short.

 k.    The nail spacing at the plywood panel edges of the shear wall(s) may be too far apart at the
 plywood panel edges, and/or the nails are the incorrect length or diameter.

 l.         Horizontal blocking may be left out at a horizontal plywood joint in the shear wall.

m.     Holes were drilled in the tension half of the stud or near the point of maximum moment.

n.       At end walls where the floor joists run parallel to the foundation wall, blocking between the 1^st,
2^nd, etc. interior joist space(s) may have been left out or removed for ducts, pipes, wires ,etc.
The block spacing is significant.

o.    In all blocked joist spaces the minimum joist spaces must be at least as wide as the blocks
are high.

p.    The sub-floor above the foundation may not have been nailed to the 1^st, 2^nd,etc. interior joists
at the correct nail spacing; or the correct number of nails were not used to nail the sub-floor
to the blocks; or the nails are not the correct length or diameter.

q.       The sub-floor is not a rated sheathing.

r.        When a stairwell or other opening is in the floor-ceiling diaphragm, adjacent to and less than
4 feet from a foundation wall with a backfill, the top plates of the wall become a horizontal
beam. Depending on conditions, the beam is constructed by adding plates to the top and
thru-bolting all the plates together. The lateral  load on the beam is blocked into the
floor/ceiling diaphragm through headers to the inside of the opening. If this is not done
correctly the top of the foundation wall will deflect into the opening. The grade, species, and
size of the top plates are significant in determining the number of pieces to us for the beam.
The size of the bolts are important in order to determine the spacing of the bolts. All bolts
used in wood foundations should always be hex-head machine bolts with washers. (Never
use carriage bolts).
          

The wood basement wood floor is up-lifting or sliding or sinking.

Causes:

a.       Uplifting: The lateral soil loads at the bottom of opposite foundation walls are
       forcing the wood floor to rise near the center. A short kneewall under the floor joists and
       connected to the floor joists will correct this. Also, bearing walls, shear walls, partitions, or
       posts on top of the floor will do the same thing.

b.       Sliding: This can occur when a high backfill is opposite a walkout wall. Sliding can occur if there
       is no frost wall or anchor wall under the walkout wall; or if the wood floor is not adequately
       connected to the top of the frost wall. Nailing patterns become significant at the bottom of the
       walkout wall where it connects to the frost wall.

c.       Sinking: This occurs when the spacing between the sleepers is too wide for the width of the
       floor joists or floor joist spacing, or if the sleepers themselves are too narrow in width to
       adequately transfer the floor load to the gravel and ultimately to the bearing soil; or if there are
       no sleepers and the floor joists rest directly on the gravel under the floor.

d.    Uplifting near walls: The plywood floor system has not been cut back 1/4" away from all wall
        studs.

e.    Center barring wall:  Walls are not supported by the correct size tee under the wall.

Need design help?  Call us at 810-955-4305 or e-mail us at woodbasement@comcast.net.

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.
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