When building a birdhouse, you can choose from a variety of woods that will provide a haven for wild birds for years. Wood is ideal for birdhouses because of its durability and affordability.
Most types of solid wood are fine for birdhouse building. Among the longest-lasting and decay-resistant woods are cedar and redwood, but a B- or C-grade exterior plywood is also a good choice. You can also use teak or other exotic woods, but they are more expensive.
Wood for birdhouses should be at least 3/4-inch thick to give nesting birds adequate insulation. If you use plywood, paint the outside or coat it with a clear polyurethane finish designed for exterior use.
Since birdhouses are usually small, you can often find good wood for your project among your local lumberyard's scraps. You can also recycle wood from old furniture, houses or construction projects. Pieces that are 8 by 12 inches are large enough for most birdhouses.
Painting the wood a bright color and decorating it with designs makes for an attractive birdhouse, but the birds don't really care. A coat of clear stain, polyurethane or earth-toned exterior paint will keep insects and the elements from damaging the wood.
Don't use pressure-treated wood, since toxic chemicals or vapors could leach out and harm the birds. Never paint the inside of the birdhouse for the same reason.