Is 45 degrees too steep for a stair?
Tuesday, March 24, 2020
A stair at a 45-degree angle is not allowed by code due to the maximum riser and minimum tread standards. The maximum riser allowed by the International Residential Code (IRC) is 7-3/4”, but a 7-3/4” tread is smaller than the minimum tread depth of 10”. Conversely, matching a 10” tread to a 10” riser would exceed the 7-3/4” max riser. It’s a no go either way.
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