How do I keep the rain out of the treehouse?
The most obvious answer is with a good roof. In more detail though, you should use a pitched (sloping) roof of at least 30 degrees (about 1:3) rather than a flat roof, you should overhang the walls by 10% of the width of the treehouse and you should avoid rainwater draining onto any deck areas. It is much easier to waterproof a treehouse if branches or the trunk do not pass through the roof. Branches that pass through walls will be less of a problem as the walls are sheltered by the overhanging roof, although heavy rain will run down all branches.
