The weight of a fire door is a key factor in determining which closer will operate most effectively with it. If you are installing a door for the first time, you will probably be able to obtain its weight from the manufacturer – some even provide handy weight calculators on their websites – but what if you are faced with a door that is already in place?
Fortunately, there is a useful formula which can be used to provide a good approximation of any fire door’s weight.
The ‘density formula’
Each type of timber used to construct fire doors has its own density, expressed as its weight in kilograms per cubic metre. For example, the core of an FD30-rated door could typically be made from European redwood, which is a softwood with a dried weight of around 510 kg/m³.
Dried hardwood densities can range widely from poplar at about 450 kg/m³, through Sapele at 640 kg/m³, to oak which is about 720 kg/m³.
If you are able to identify the type of wood used, the following formula will give you your door’s approximate weight.
Door Weight (kg) = Density x Door Height (mm) x Door Width (mm) x Door Thickness (mm)
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For example, a fire door 2 metres high, 850mm wide and 44mm thick, using timber with a 510 kg/m³ density, would be calculated as follows:
510 (density) x 2000 (H) x 850 (W) x 44 (T) = 38,148,000,000 = 38kg (to the nearest kg)
1 million
Where the density of the wood core is unknown
If you cannot identify the exact type of wood used, but can establish whether the timber used is hardwood or softwood, our experience has shown that you can get a ball-park door weight by assuming a density of 385kg/m³ for a softwood door and 585kg/ m³ for a hardwood one.
Feeding these values into the formula would produce results (again, to the nearest kg) of 29kg for a softwood door and 44kg for a hardwood door.
Finally, allow for the hardware
Having calculated the approximate weight of the door panel itself, add on the weight of any door hardware, such as handles and kick plates (which are small enough to be easily weighed on scales), and consider the impact of glazing. If there any vision panels, the weight will depend on whether the single, double or triple glazing is fitted. In weight checks Rutland have performed, a double-glazed unit (DGU) weighs about the same as the section of hardwood core removed from the aperture, while a single-glazed unit is roughly equivalent to the softwood removed to make an aperture.
When choosing the right door closer for the job, the best practice would be to select one with a power rating a grade or two above what your door weight nominally requires under the EN1154 standard (see table). This then allows leeway not only for the elements of approximation that have gone into your door weight calculations, but also for real world variables – for example, the impact of air pressure – that can affect a fire door in operation.
Door closer sizes for different door weights as set out in EN1154
*For fire doors, it is usually recommended to fit a minimum size 3 closer
We’re here to help
In an ideal world, we would all know the exact weight of every fire door we encounter, but we hope the above suggestions help to overcome some of the problems the real world can present!
If you need specific advice, we are always glad to help, so give our team a call on 01246 261491 or email us.
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