Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 29·2.35
Factory-made metal chimney wall penetration and access
Sleeves should be provided where chimneys pass through walls to prevent damage from thermal expansion, and joints must remain accessible for gas-tightness checking rather than being concealed.
Where a factory-made metal chimney passes through a wall, sleeves should be provided to prevent damage to the flue or building through thermal expansion. To facilitate the checking of gas-tightness, joints between chimney sections should not be concealed within ceiling joist spaces or within the thickness of walls unless proper access is provided.
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