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.
Thanks very much,
You have me confused.
3x3x3/16 is light for lintel iron
Lintels carry the masonry load over openings.
In order to carry the load, the masonry rests on the lintel.
Where does this gap come in?
(top posted for your convenience)
Keep the whole world singing . . . .
DanG (remove the sevens)
This is for a kiva style fireplace. I'm building an arched opening into
the firebox so won't need the lintel there. The damper manufacturer shows
two places for a lintel. One is for the span across the opening. The
other is up near the top of the smoke chamber to support the flue liner.
Their recommendation is the 3x3x3/16". I will have brick on top of this
piece of steel as well as at the sides (ie. completely "embedded" in the
fireplace masonry). I don't want the mortar joints cracking down the road
due to expansion/contraction so was asking how much "air gap" around the
steel itself I should use to allow for the steel. Make sense?
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?
Hmmm, hadn't thought about stainless. I purchased just the standard angle
already. We see very little moisure here in NM but I may have to make some
phone calls tomorrow to see what a stainless piece will cost. Thanks for
Coefficient of expansion for steel is about 0.000007 per degree F. For
brick about 0.000003. For a 300 degree rise, if the lintel is 24 inches
long, the total expansion of the steel will be --
TE = 0.000007 x 300 x 24 = 0.05 inches.
The brick will expand about half as much, making the differential expansion
about 0.03 inches, totally inconsequential I would think.
Many years ago, my neighbor and I built a brick grill on the property line
for joint use. We used imbedded rebar for the grate right above the
firebox. Never noticed any adverse effects.
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