I am a big suporter of many of these products especially for heritage buildings where replacement is not an option. (and not just for big old substantial doors, sometimes a plank door with just a couple of ledges can be part of the listed provision.)
Yhey have convinced English Heritage and National Trust of the benefits. The key is accurrate examination of the test certificates to ensure that the test reports and the samples tested are relevant to the case in point. Someimes companies put together large panels of various different materials and thicknesses to obtain a satisfactory test of various samples in one hit. If this is the case then you have to question the relevance of a panel test being used to justify door construction.
It is most unlikely that the manufacturer will have tested an identical door with the same joints, glues, beading profiles, density of timber as the one that you are upgrading. Provided the evidence derived from the test is used carefully it can inform your decision but will never be definitive. In heritage buildings we aim to use this information to improve a door TOWARDS a particular fire resisting standard, fully recognising that we can never say with absolute confidence what its fire rating will be.
Why face all this hassle if there are other options? But also beware- there are several door manufacturers marketing fire doors - particularly hardwood doors who have simply copied other peoples test results and never actually submitted their own product for test.Is this any better than a door upgrade? If buying a purpose built fire door look for a reputable company such as a member of the ASDMA, BWF certification or similar.
But as others have pointed out, for upgrades standards of application on site are absolutely critical.
