James "Cubby" Culbertson wrote:
Hiya,
I'm currently constructing an outdoor fireplace. I intend to use 3x3x3/16"
angle in a couple of places where I'll need a lintel. I intend to paint it
with high temp paint. Anyway, I'm wondering just what sort of clearance I
need around the steel for thermal expansion? Obviously I need some mortar
in there to hold the bricks together but just not sure of how much of a gap
around the steel I need.

No matter how conscientious you are about painting that lintel, it will
eventually rust. The rust expands, the mortar cracks - I'm sure you've
seen it a million times. Since you're doing it yourself and there's a
potential elimination of maintenance, have you looked into a stainless
steel lintel? It doesn't sound like you'd need a lot, so the premium
would probably be under a $100. Is it worth it to you?

R