Frank Z wrote:
I'm not sure how much a 31" length of steel will expand. My
guess is less than 0.5mm. To stop the masonry cracking
at each end of the lintel, I stuck some foam draught excluder
onto each end of the lintel so it will simply be compressing
the foam, not the masonry. I guess plaster will expand when
hot too. With a bit of luck, it'll expand the same amount as
the steel - but that may still not prevent cracks occurring.

The coefficient of thermal expansion of mild steel is about
0.0000126/DegC. Assuming a possibility of a 100 degree
temperature change, that's 0.03906", near enough 1mm.

Perhaps I'll follow Andrew's idea and stick something onto
the lintel, like brick tiles or something... not sure...

I don't understand your setup. Have you used a square section
tube, or what? Can you supply an ACSII cross-section?


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