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PATHChat
| SUBJECT: |
RE: Exterior basement walls(NAHB Research Center)
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| FROM: |
DEAN YOUNGKEIT
guruofhousing@netscape.net
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| DATE: |
4/14/1999 8:22:00 PM |
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Gary:
I did a cut and paste from the NAHB Research page for
you. http://www.nahbrc.org/
Question:
I am considering buying a house that was
built five years ago with a pressure-treated plywood
foundation. I am interested in a short rundown on
pressure treated wood foundations. What are the plusses
and minuses, particular items to look at during a home
inspection, etc.?
Answer:
Description: A pressure-treated plywood
foundation, typically referred to as "Permanent Wood
Foundation" or simply a wood foundation,is a foundation
wall type constructed of pressure-treated 2x6 or 2x8
wood studs and pressure-treated plywood. The wood
preservative is similar to that used for decks, but has
a higher level of preservative content (0.6lb.per cubic
foot instead of 0.4 lb. per cubic foot).The use of this
preservative, in combination with proper exterior
waterproofing and drainage,prevents fungal decay. There
is not enough experience with these foundations yet to
know if they will eventually suffer from decay, but at
least one manufacturer is offering a 75 year warranty.
Wood foundations may be used for full basements
(finished or unfinished), crawl space walls, stem walls
below slab edges, and floors below grade. Wood
foundations can provide several advantages including:
reduce construction time and construction in any
weather; ability for carpentry crews to build the
foundation, then move directly to framing the rest of
the home; energy efficiency -- stud cavities can be
easily insulated; dry basements; absence of cracking;
and ease of finishing-off the interior --drywall can
simply be applied to the studs. These types of
foundations vary in cost--they may be more or less
expensive than conventional foundation types.
Inspecting: When looking at a house with a wood
foundation become familiar with the design practices
for wood foundations or hire an engineer or home
inspector who is. Be sure all requirements were
followed faithfully by the builder. Understand that
many details will be concealed. Key items to check
include: sizing, grade, and spacing of wood framing
members, and grade and thickness of sheathing materials
(typical basement walls use 2x6 or 2x8 studs at 16" or
12" on center, and 5/8" thick plywood.); proper
preservative treatment of wood members, as indicated by
the treater’s stamp; use of proper corrosion-resistant
fasteners; exterior polyethylene water barrier
(protected above grade), proper backfill, and proper
drainage; floor slab poured against bottom plate of
wall; Proper fastening of walls to floor system. signs
of excessive bowing or cracking of studs, or of
movement of top of wall; and signs of water entry.
Consult the design, fabrication,and installation manual
for the Permanent Wood Foundation for detailed
information on proper construction. The manual is
available from the American Wood Council (AWC) by
calling 800-890-7732; or on the internet at
http://www.awc.org. The AWC also publishes Basic
Requirements - Technical Report No. 7 for wood
foundations.
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Partnership for Advancing
Technology in Housing (PATH)
451 7th Street, SW, Rm. 8134
Washington, DC 20410-0001
Telephone: 202 708-4277 Fax: 202 708-4250
E-mail: pathnet@pathnet.org |
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