By continuing to view this resource, you acknowledge that Housebuild is not liable for any injury incurred as a result of the information provided on this page.
Care and attention to detail are required in this type of lean-to construction when fixing the head of the rafters in order to ensure rigidity while still ensuring the party wall contains sufficient fire-stopping and sound insulation. The sketches opposite show the approach recommended for such details. The rafters and ceiling joists are omitted from the sketches for clarity.
Diagram D57 - Duo pitched roof with party wall detail with fire stopping
Diagram D58 - Duo pitched roof with party wall strapping detail
Detail – Shows positive fixing of rafters to prevent horizontal thrust at eaves.
Diagram D59 - Duo pitched monotruss
Diagram D60 - Duo pitched roof with party wall
Prefabricated mono trusses as shown above can be used as an alternative to “cut timber” back-to-back lean-to construction.
Diagram illustrating a typical “back-to-back” detail where prefabricated mono trusses are used.
Lean-to Roofs
Diagram D61 - Lean to abutment detail
Abutment Detail
The diagram above shows the flashings detail for abutments of porch and lean-to roofs. Flashings should be built into the cavity tray as shown and ventilation should be provided to the roof as explained previously.
Fire safety Ventilation Roof Cavity External insulationCavity wall insulationUnderfloor insulationWall tiesAir to water heat pumpAir to air heat pumpAir to ground heat pumpTimber frameCeiling insulationRoof insulationJoistsTime and temperatureFire stoppingFire masticFire wrapsFire boardSound insulationTongue and grooveBead insulationPumped insulationPump cavityExternal wall insulationRoof lightsFire doorsWall tilesVentilationEaves boxMechanical ventilationNatural ventilationFire cableDamp proof membraneDamp proof coursePitchUnderfloor heating pipesPilingPIPlanning permissionPlumbingPlanningPlasterboardEmployers liabilityPLPlugsStructurally insulated panelsSolar panelsFireline boardELElectric showersLight gauge steelBER