Historic Structural Detail: Stairs

by Don Friedman on May 17, 2016

A lot of old buildings with wood-joist floors have their stairs contained within brick enclosures. It’s an early form of fire-resistant egress path. So how do you create a non-flammable stair under those circumstances?

Here’s the top side of the stair, looking down (my apologies for the vertigo):

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And here’s the underside, looking up:

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Each step is a single block of ashlar stone, set into the side walls and spanning between those walls. The top of the block is the tread, the front face is the riser, and the bottom and back face form an inverted stair-like configuration on the underside. You’ve probably seen this effect elsewhere.

It’s a ridiculously simple way to build a fire-resistant stair as long as the stone blocks are strong enough o span between the walls, and they are. Don’t underrate simplicity.

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