Lean to Rafter Calculator(aligns with spreadsheet)
Pitch of Roof		degrees
Tile Data Concrete Interlocking Plain tiles Natural Slates Artificial Slates Red double pantile Clay single pantile Clay double pantile Fibre cement slates Natural Welsh slates		60	kg/m2
Battens and felt		5	kg/m2
Timber 100 x 50 timbers 150 x 50 timbers 200 x 50 timbers 225 x 50 timbers		8	kg/m2
Insulation		5	kg/m2
No plasterboard 1 layer 12.5mm plasterboard 2 layer 12.5mm plasterboard 3 layer 12.5mm plasterboard 4 layer 12.5mm plasterboard		15	kg/m2
None Ceiling (5 kg/m2) Services (3 kg/m2) General contingency (8 kg/m2)		0	kg/m2
Total		93	kg/m2
On plan		102.6	kg/m2
Permanent Load		1.01	kN/m2
Design Snow load 0.60 Design Snow load 0.75 Design Snow load 1.0		0.60	kN/m2
Roof Snow Load adjusted for pitch		0.60	kN/m2
Total		1.61	kN/m2
Rafter	Data Entry
Clear Slope Dimension		m		Eff
Clear Span on plan	1.86	m		1.96
Centres		m
Trial Depth		mm
Trial Width		mm
timber grade	C16 C24
			stress	deflection
Rafter satisfactory			72.2%	97.3%