Common problem situations include tight workspaces, fittings installed too closely to structural timbers. You can often pre-solder fittings that must rest against structural timbers or be installed deep inside cantilevers or wall.
Solder deep-set fittings, like this freezeproof sillcock, to their pipes before installing them.
When you can't avoid soldering against studs or joists, you can keep from scorching the wood by sliding a double thickness of sheet metal between the fitting and the structural member.
Use a double thickness of sheet metal to keep from scorching the wood.
It is handy to keep a 6-inch fold of sheet metal in your toolbox for this purpose. The sheet metal must have two layers. Plumbing outlets also sell squares of woven fireproof protective fabric, which also work well.
You can also use a flame shield of fireproof woven fabric to protect larger areas.