In the case of CE EN13229 test for inset stoves, the safe distance to combustible materials above the stove is measured and this distance should be clearly stated in the handbook which came with your stove. It should also be referenced on the stove's CE dataplate. However, measuring a safe distance to a combustible 'shelf' or mantel is not actually a requirement of the CE EN13240 test for free-standing stoves, although it is for the sides and rear of the stove.
So, how can you determine the safe distance to a combustible or wooden mantel when a free-standing stove has been installed? Unless the manufacturer stipulates this distance in their handbook and this 'safe distance' has been derived from a valid set of tests under a wide-range of installation scenarios, then really you're on your own.
The view that Hetas take in these situations is, where the manufacturer has not supplied the safe distance, then the installer is advised not to fit a combustible mantel or to fit the stove where there's an existing combustible mantel which is being retained. For years installers used a simple rule of thumb based on the safe distances used for flue pipe. Unfortunately there is no basis for applying this rule to combustible mantels and therefore Hetas no longer support this and therefore we won't repeat it here.
The problem a manufacturer and installer has is that there are just so many variables in the way a stove can be fitted and the impact this will have on a combustible mantel. Does the stove fit well inside the front of the fireplace or is it a rear flue installation where the stove usually sits proud of the fireplace so that more direct heat is applied underneath the mantel? What is the depth of that mantel? A deeper mantel will be subject to more of the rising heat because it prevents it from safely passing. Is there a lot of space around the stove in the fireplace so that heat can gently radiate and avoid a potential heat build-up, which could create intense heat underneath the mantel? What happens to safe distances to combustibles (including the side and rear) if the stove is overloaded and over-fired and what if the door is inadvertently left open after re-filling and the stove is also left unattended so that flames exit the fire chamber – is there a sufficient safety margin? Over the years as stove dealers and installers we've witnessed many a scorched wooden mantel where the previous installer has ignored these basic safety considerations.
Considerations when installing a wooden mantel
Is there space around the stove?
How Deep is the mantel?
How proud does the stove sit?
How far away is the mantel?
Can you minimise the heat impact?
Can you be sure it is really safe?
All of these are sound reasons why many manufacturers do not recommend using combustible mantels – a safe height for one installation could be unsafe for another installation. However, an experienced stove installer who's on site should be able to take all of these factors into consideration and to make a safe 'belt and braces' judgement. Alternatively, there's now a good choice of highly convincing 'wooden' mantels made from non-combustible specially formulated cement which will allow you to position your 'wooden' mantel as close to the stove as you want.