Fireplace hearth flush with wooden floor

Hello all
looking at fitting a fireplace hearth in a new build which is flush with a wooden floor - no step.
Sales guy at suppliers stated that this was against building regulations for a solid fuel fire - is this correct ?? I have seen such an install before.

Any ideas, what exactly are these regulations- had though of cutting into concrete floor to provide a space to insert a standard hearth. Another optipn was a solid fuel insert stove into the fireplace and using a 1+ inch gnaite slab as a hearth. would this suffice or would I still be faced with problems with cracking due to heat etc

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1650,en.pdf

look at paragraph 2.18

there is no requirement for the hearth to be over the floor level.

but there is a requirement to keep any combustible material 500mm from the front of the fireplace, and 125mm on either side of the breast.

plus the hearth needs to be at least 125mm thick... and there should be no combustible material a further 50mm away..... this will probably cause problems in a typical floor build up as the insulation is usually only 150mm under floor level...

if you are thinking of cutting into a concrete floor to achieve this i would advise against it, for the reason above, and also because of the loss of structural stability of the floor by cutting a (approx) 1.5 x 1 m hole in it...