External door steps, upvc threshold height and the 150mm dcp.

4 Mar 2011
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United Kingdom
To the left is the extension, on the right at 90deg to this is the original house wall. To the right of the patio door is next doors garden wall, running parallel with the extension. I have removed the existing concrete slab, which was less than 150mm below dcp level. We had no issues stepping in or out with the previous concrete level. I planned to pave the area around these two doors, 150mm below the dpc with a channel drain running along both walls (we have dogs and I want to be able to keep it clean).


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However it has come to my attention that the maximum outdoor step rise is 150mm.

Do you measure step height to the threshold level, or internal floor level?

My assumption is that you measure to door threshold, so paving at 150mm below dpc puts the step height at around 260mm.

If I was to build a 150mm step down from the threshold it would be roughly 40mm below the dpc. On a single doorway I understand this would be a negligible breach of the 150mm rule. Unfortunately with the two doors so close to each other the area of step close to dpc would be much larger. I feel two individual steps close to each other would look clumsy, and likely present a trip hazard. It actually makes more sense to raise the whole patio near the doors to the 150mm step level, and then step down to the rest of the patio. However this massively breaches the 150mm dpc rule.

Basically I'm open to suggestions and guidance as any current search won't bring up a definitive answer.
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