Building Paper Under Vinyl
After looking at picture D on page 24 of the February issue of
JLC, I wondered why sheathing paper is not required under vinyl
Editor Don Jackson responds: Though it's always been a good
idea to use it, the IRC didn't require building paper under
vinyl siding in earlier editions, allowing it an exemption in
Table R703.4. However, that's been changed in the 2006 IRC:
Vinyl, like other claddings, must now be installed over a
"water-resistive barrier" (called a "weather-resistant
sheathing paper" in previous editions).
Page 38 of January's JLC (Q&A, "Sealers for Porch Floors")
states that "research has shown conclusively that solid wood
products back-primed with a WRP [water-repellant preservative]
retain paint better — and perform better overall —
than those coated on one side only."
On page 26 of the accompanying Coastal Contractor [a supplement
to JLC readers who live near the East Coast], the advice is
exactly the opposite: "... one thing you never want to do is
back-seal the bottom surface of any decking. The top surface
will inevitably break down quickly due to UV exposure, and once
it does, the wood will absorb water. If the bottom surface is
sealed, the boards essentially fill up like troughs, hastening
the deterioration of the remaining finish and the wood
In my home-inspection business I frequently rely on information
supplied by the experts and building scientists in your
publications. Contradictory guidance is frustrating. It would
be relatively simple for building scientists to compare notes
or research and come to an agreement on a best practice for
back-priming exterior decking.
Chapel Hill, N.C.
Editor Don Jackson responds: While a "one-size-fits-all"
solution would be nice, in this case there isn't one. The two
applications you refer to — a partially protected T&G
Doug fir porch floor and an exposed coastal ipe deck —
are very different animals.
It's well established that it's futile to put a film-forming
finish, like paint or a solid-color stain, on a wood deck: The
finish will break down, allowing water to get into the deck
boards but preventing it from easily getting back out, thus
hastening the deck's demise. That's why the treatments most
often used on decks are penetrating water-repellant
preservatives, which help keep moisture out of the wood and
resist UV degradation but don't form a film.
All of these products have to be maintained with regular
cleaning and recoating. How regular depends on many factors,
including sun exposure, climate, type of wood, and how durable
the finish product is. One of the beauties of ipe is that it
weathers well without surface treatment, as long as the client
doesn't mind the silver-gray color it takes on.
The recommendation in the Coastal Contractor article not to
seal the bottom of a deck, but to allow good air circulation,
is consistent with what most deck-finish manufacturers
As for the traditional painted porch floor, Bill Feist's
recommendation to seal all sides of each tongue-and-groove
floor board is based on solid field evidence.
The National Park Service has been using this method for many
years when replacing porches and has found that it greatly
extends the service life of the flooring by helping to prevent
cupping and checking. It also makes the top coat last longer,
for the same reason. The NPS is careful to use only one coat of
primer, an acrylic, which doesn't completely seal the wood but
allows water vapor to escape, thus allowing the porch floor to
dry to the bottom if necessary.
More specifically, Feist's recommendation to use a paintable
water-repellant preservative for the prime coat is based on
field-testing done at the Forest Products Lab, in which this
type of product outperformed conventional paint primers on
hardboard siding. Earlier work at the lab had established that
exterior wood holds paint better if it's primed on all
Quick Newel Layout Tips
I read the article "Quick Layout for Stair Rails and Balusters"
(2/06) with great interest. I marveled at its simplicity and
usefulness, but one thing caught my eye.
On the subject of shortening the newel, the example newel is a
box type with a built-up base. So if you were to lay the rail
on the tread nosing to mark the newel, you would not actually
be touching the newel in the intended location, because of the
3/4-inch built-up base. In this case, the newel would have to
be shortened more, because the rail line would extend further
by the 3/4-inch thickness of the base while descending at the
given angle of 37.3 degrees.
Author Phil Springer responds: You have a good eye. Yes,
the mark would have to be adjusted to compensate for the
3/4-inch skirt wrap.
This newel was purchased with the base wrap already attached,
so after making my mark on the post while the rail was down on
the treads, I referred to my full-scale drawing of the rise and
run of the stair. I measured 3/4 inch back from the front
(nosing) corner of the triangle and drew a line up
perpendicular from the base to the hypotenuse to find the
additional amount of height that needed to be cut off the
bottom of the post. This amount can make a difference, as many
newel posts don't leave much extra room for the rake cut of the
handrail to land. Box newels take quite a bit of time to cut
and fit well, and having to cut them off a second time gets
expensive. Thanks for pointing out this potential
I'd be lying if I said that I've never made that mistake
before, but the days you don't get richer, you get smarter. Now
I generally remember to cut the extra length off the first