Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 48·3.25
Combustible material beneath constructional hearth
Combustible materials placed beneath a constructional hearth must maintain either a minimum 50 mm air-space from the hearth underside, or be positioned at least 250 mm below the top of the hearth.
Combustible material should not be placed beneath a constructional hearth unless –
(a) there is an air-space of not less than 50 mm between the underside of the hearth and the combustible material; or
(b) the combustible material is not less than 250 mm below the top of the hearth.
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