Protecting projects from sun and rain takes know-how
When
it comes to building outdoor-tough wood projects, you need a new
understanding of glue, finishes and fasteners.
Don't be fooled by product label claims that describe regular wood
glues as "water-resistant"-that alone isn't sufficient for outdoor duty.
Choose
a product designated either as "weatherproof" or "100 per cent waterproof."
My favourites include PVA carpenter's glues carrying a Type II
water-resistance
rating or polyurethane glues. Many two-part epoxies perform well outdoors,
but they're more expensive and often troublesome. Why bother when the right
kind of single-part glue does the job?
While it's true that ordinary steel screws and nails will survive
outdoors for years, they'll streak your woodwork with rust, even through
paint. You
need something better. And even though gold-coloured deck screws resist
corrosion well, you're better off with hot-dipped galvanized or
stainless-steel
fasteners. In fact, these are essential for the new arsenic-free
pressure-treated lumber that's on store shelves now. This lumber is
substantially more
corrosive than the older-style pressure-treated wood, which in turn is more
corrosive than untreated lumber.
Whatever material you use, reduce wood-to-wood contact areas as much as
possible. Trapped water promotes rot. Separate adjoining parts with spacers,
allowing joint areas to dry after a rain.
The finish you choose should depend on your expectations. If you want a
stained finish that resists weathering and lets the wood's beauty show
through,
fine. Just be prepared to maintain that finish every 12 to 36 months. Since
the late 1980s I've used Sikkens Cetol on outdoor wood, and it works well,
particularly when I sand all surfaces with an 80-grit abrasive before
applying.
Film-forming finishes aren't too much work on large, flat surfaces, but
in situations with lots of nooks and crannies, consider a peelproof
approach.
For the past three years, CHW contributing editor and outdoor project
specialist Rick Campbell has applied Circa 1850 Tung 'N' Teak Oil on outdoor
work
that still looks as good as the day it came out of his shop. It can't peel
since it soaks in, yet it keeps wood from greying. For projects I never want
to futz with again, I use a Canadian product called Lifetime Wood Treatment
(
www.valhalco.com).
It's a powder you mix with water and spray or brush on. In less than a day,
the wood turns a rich grey colour, protected against decay by the nontoxic
formula.
It should even work on a mailbox.
. sand before finishing to extend the life of all film-forming exterior wood
coatings.
. use nothing finer than an 80-grit abrasive before you apply exterior wood
finishes.
. maintenance-free, rot-proof composite deck stock is useful for more than
decks: it makes hardy outdoor tables and benches.
. rounded or chamfered edges hold a finish better than square ones.
. hot-dipped galvanized ardox nail
. hot-dipped galvanized carriage bolt
. stainless-steel flathead wood screw
BOTTOM RIGHT
. choose weatherproof glues for all exterior applications: ordinary
water-resistant wood glues are not sufficient for use outside
