Homeowner Forum / Construction / March 2006

i have heard of building without sheathing--in fact in my young and
poor days i built an outdoor sauna without sheathing.  the most
important function of sheathing is structural...it provides resistance
to racking.  diagonal braces (either let-in 1x or steel) can also serve
this function.  not that i'd recommend building without sheathing.  it
also provides a layer of protection against air infiltration for one
thing.

I think adding sheathing is a good idea.  you might want to walk around
the house and make sure there aren't issues that adding a half inch of
thickness would cause...like how are the windows and doors installed?
if you sheath around them, will water still be kept from penetrating
the structure. another question to ask is what kind of sheathing.
presumably, if your house has stood for almost 30 years without
collapsing like a house of cards, it must be adequetely braced.  so you
could consider foam sheathing (like R-board or the like) or perhaps a
product like Bilt-Rite.  Good luck.

Nawh, some builders do the minimum necessary to get by with...

Assuming that the HardiPlank is nailed to every stud and the studs are on
16" centers, I don't think that you will get waves in it... Personally, I
would try to make sure that the butt joints line up on studs...

My philosophy is that is it's better to start with an airtight house and
worry about adding ventilation than a drafty house and trying to stop all
the leaks...

Depending upon the style of the house, stucco might also be an option for
you... Putting sheathing in addition to stucco is probably a bit of
overkill... You still have to put some sort of vapor barrier between the
stucco and the wall studs -- tar paper, Tyvek, etc...

Good idea.  Mine looks great after 2 seasons.  Like it was painted
yesterday.

Sheathing will make it easier to put the Tyvek and siding on straight.
Your marking and nailing surfaces will be more uniform.  The drawbacks
are the cost. I think it is now $12 around here for 7/16 OSB 4x8. (I
only paid $5... before the Iraq war and Katrina.)  Another drawback is
the sheathing will hide the studs, so you'll have to make sure you mark
their locations since the Hardiplank is supposed to be nailed to the
studs, not the sheathing.

No.  Probably the strategy used in your house was to let it breath to
prevent mold... smart in a hot humid climate.  And cheap.  Plus as
someone else said, as long as you have bracing you don't need the OSB
for bracing... but the OSB sure will make the house seem sturdier in winds.

I would avoid stucco in GA... seems like that would cause problems with
wood rot, especially the fake Dryvit "stucco" that is causing lawsuits
in NC.

If you're replacing with Hardie horizontal lap siding, you have to double up
the studs.  You can't nail (or screw) as close to the end of the siding as
you would in wood siding.

If the house has integral bracing in the walls, for instance a 1X4
diagonally cut into the studs at the corners, you don't really need OSB for
this purpose.

Many builders also use OSB on the walls prior to Hardie lap siding as its
much easier to nail the product to the studs.  Also, the siding won't mirror
a wavy stud wall as much.

IF, IF, IF you have doubled up studs, a straight non-wavy stud wall, and
integral wind bracing, you don't need OSB.  You can use 1/2" fiberglas
insulation bonded both sides by aluminum foil for slight insulation
increase.  I did my standalone garage in that fashion.  The wall length is
only 20', so it was easier to maintain straightness and nonwavy appearance.
Paying attention to nailing (or screwing), not to compress the insulation
during the application phase of the siding.

If you have studs with excessive bow outward or inward, consider replacing
these.  The Hardie siding will mirror all imperfections.  A bowed inward or
outward wall at the sole or top plate line can be hid to some degree.  Some
use taut nylon stringline at each corner offset with a 1 by lumber from the
wall to get absolute straight reference for this.  I can't overemphasize
straight framing that supports the siding enough.

When the crew is finished, check the laps.  These may show lack of flush to
wall by virtue of gaps at the lap joints.  Be sure they're tight at the lap
joints.  Little caulking should be needed here.  Corner, butt, and inside
joints may be another matter.  These should have some minor flex.  This
allows growth and shrinkage due to moisture and heat.  Proper caulking will
absorb the flex.