Right, just been having a browse, and found this
Quote:
Temporary ramps
In situations where for whatever reason a permanent ramp cannot be installed in an existing building, a temporary ramp may be a preferred solution (though when designing new buildings this would not be acceptable).
Temporary ramps, especially long or heavy ones, can be awkward to handle. It may also be difficult to provide a top landing of recommended size. A temporary ramp’s rise should not exceed 500mm, and the gradient should not exceed 1:12. All ramps should be firm and secure in use.
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source
http://www.cae.org.uk/guidance_ramps.html