We often get asked – ‘Do I need to leave a layer of ash in my wood heater?’
A bed of ash can actually be quite beneficial. It can take a while for the firebox to heat up from a cold start, so a bed of ash can help to get the fire going more quickly and to also burn more efficiently, as the ash helps to insulate.
Too little or no ash left in a wood heater can cause damage to the base of the firebox, as metal firebox bases can become warped over time, while other types of materials can begin to crack. Too much ash, however, can block the airflow from the vents around the base of the firebox.
As a guide, when cleaning out the ash, leave a layer of approximately 10 – 20 mm, but check your manufacturer’s guidelines, as their recommendations do vary between different makes and models.