HIP ROOFS Created BY Michael Martin July 2004 / revised may 2007

Hip & Valley Roofs “3 Basic Principles” All ridges must be level & parallel to wall plates All rafters must be placed at 90° to wall plates – regardless of the roof shape All hip and valleys must bisect the angle of the corner Roof members are set out on centre lines (Page 316 of text)

Components - handout Wall plate Ridge Centering rafter Crown end Hip Common rafters Creepers Purlin

Set out – all relates to center lines Centring Rafters Ridge Hip Crown end rafter

New Members – summary to complete in handout Hip – Inclined member from wall plate at external corner to end of ridge Crown end rafter – special rafter running from wall plate (center span position) to end of ridge Creeper rafter – rafter cut in length to join hip

Set out Ceiling frame also depends on set out of rafters Set out as opposite Refer to handout Page 3

The Ridge for a hipped roof Length = length of the building – width of building + rafter width See hand out for reference, last page

Pattern Rafters – page 347 Now include Common / centering Crown end rafter Creeper rafters Centre line to centre line first

Pattern Rafters Remember Common / centering – reduce by ½ thickness of ridge Crown End – reduce by ½ thickness of common rafter / ceiling rafter Creepers – are calculated on pattern – by determining long point

Determining long point of creeper 1st mark out spacing from centre line 2nd take off half mitre thickness of hip 3rd add on half thickness of common rafter You now have long point Continue to mark out other creepers

Pattern Rafter – page 347 or handout

Bevels – common rafters & centering rafters – from P 333 Plumb bevel Rise Level bevel ½ span

Bevels - hips Create another triangle in the roof Plumb bevel Level bevel Rise Plan length hip

Bevels - hip Relate to true length per metre again As you do for common rafter

Bevels – hip (eg) 30° pitch Rise per m run – tan 30° = .577 Use Pythagoras to create plan length of hip √1.0² + 1.0² = 1.414 (plan length of hip) True length per 1.414 run √1.414² + .577² = 1.527

Bevels - hip True length 1.527 Rise .577 Plan length hip 1.414 You have now created that new triangle You can reduce this to fit steel square Take bevels from this True length 1.527 Rise .577 Plan length hip 1.414

Bevels You now have your first four bevels Plumb bevel common rafter Level bevel common rafter Plumb bevel hip Level bevel hip In a hipped roof, there are eight (8) bevels all up

Bevels These 8 bevels can be developed in a number of ways Eventually you’ll choose which one suits you Geometric (we will draw ourselves) Steel square (from P339 text) Direct method (from P343 in text) Or combined triangles (not in text) We will cover each one separately, one by one later

Main Roof Components 1st lets concentrate on what we know Common rafters Centering rafters Hips Creepers ridge

What we’ve done already Common rafters – set out on pattern Crown end rafters – set out on pattern Creepers – set out on pattern Hips – we need to look at further

Hip rafters Before you erect hip You have to take into account Reductions Ref: P16

Hips 1st at the ridge the hip must be reduced in length You can calculate it or Measure it in place In principle it is reduced as shown opposite Hand out – shortening at “x”

Hips 2nd at the birdsmouth you must reduce as well Calculations of length give you position at outside of plate Typically you cut corner to give better seating Therefore birdsmouth must be reduced to suit Handout – shortening at “y”

Hips Set-out of birdsmouth on hip Top of rafters, including hips, must be on the one plane Set out of hip birdsmouth as opposite See handout

Hipped Roof Now you can build the main structure of the roof Edge bevels for creepers and hips we’ll show you in workshop Purlins we’ll look at after we develop other bevels Drawing boards next week