Broken Hip Roof. Lay out of Hip & Valley Roof Roof Pitch = 25⁰

Broken Hip Roof

Lay out of Hip & Valley RoofRoof Pitch = 25⁰


What Members define Creeper side cut



• Half Span•Common Rafter

What Members define Valley Creeper side cut




What Members define Valley Creeper side cut


Lay out of Hip & V RoofRoof Pitch = 25⁰



Lay out of Broken Hip RoofRoof Pitch = 25⁰

No new bevels need to be developed


All Bevels and edge cuts are the same as a hip roof

Broken Hip As Span is not the same the rise will not be the same


Rafter 90 x 35 @ 450 c to cHip Rafters 140 x 35Ridge 140 x 35

Common Rafter Major Span

Common Rafter Minor Span

Hip Rafter Major Span

Hip Rafter Minor Span

Valley Rafter Minor Span

Crown End Major Span

Crown End Minor Span

Centring Rafter Major Span

Centring Rafter Minor Span

Crippled Centring RafterBroken Hip

Gathering Point



With the more complex roof a roof is. It is important to plan & determine as much of the roof offsite that you can

Lay out of Broken Hip Roof

Determine Required LengthsCommon Rafter Major Span =

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰

Rafter 90 x 35 @ 450 c to cHip Rafters 140 x 35Ridge 140 x 35Rafter Spacing 300mm


Determine Required LengthsCommon Rafter Major Span

= Plan Length x Rafter Length / m= (1000 – 17.5) x 1.103= 982.5 x 1.103= 1084

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰


Common Rafter – Major SpanPlumb Cut

1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span =

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span

= Plan Length x Rafter Length / m= (675 – 17.5) x 1.103= 657.5 x 1.103= 725

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰


Common Rafter – Minor SpanPlumb Cut

• As Major & Minor Span are the same pitch the plumb cuts must be the same

1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof

= (½ Span – ½ Ridge) x Rise / m

= (1000 – 17.5) x 0.466

= 982.5 x 0.466

= 458

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458

= (½ Span Major – ½ Ridge) x Rise / m

= (1000 – 17.5) x 0.466

= 982.5 x 0.466

= 458

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof =

= (½ Span Minor – ½ Ridge) x Rise / m

= (675 – 17.5) x 0.466

= 657.5 x 0.466

= 306

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



We recall that all hips & valleys bisect corners.

In this building it means that they are at 45⁰.


To develop other Roofing Members we need to determine the plan length first


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span

= Plan Length Crown End Rafter x Hip length/m

= (1000 – 17.5) x 1.489

= 982.5 x 1.489

= 1.463

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰


Hip Rafter – Major SpanPlumb Cut

1.103

√2

0.466

1.489

1.000

Plumb Cut


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span =


= (0.675 – 17.5) x 1.489

= 657.5 x 1.489

= 979

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰



Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span =


= (0.675 – 17.5) x 1.489

= 657.5 x 1.489

= 979

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰


Valley is the same as the hip

Hip Rafter – Minor SpanPlumb Cut

• As Major & Minor Span are the same pitch the plumb cuts must be the same

1.103

√2

0.466

1.489

1.000

Plumb Cut

Lay out of Broken Hip RoofDetermine Centreline LengthCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major

Plan Length = ½ Span – Spacing + Correction

= 1000 – 300 + (1.414 x -17.5 + 17.5)

= 693 x Rafter Length / m

= 693 x 1.103

= 764

1.103

√2

0.466

1.489

1.000

Roof Pitch = 25⁰


Note these measurements are directional as it goes back towards the Top Plate it must be a negative

Creepers– Major SpanPlumb Cut

• Creepers are the same pitch as the Common Rafters. They must have the same Plumb Cut

1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Centreline LengthCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major = 7641st Creeper Minor = 406

Plan Length = ½ Span – Spacing + Correction

= 675 – 300 + (1.414 x -17.5 + 17.5)


= 368 x 1.103

= 406


1.103

√2

0.466

1.489

1.000

Creepers– Minor SpanPlumb Cut


1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major = 7641st Creeper Minor = 4061st Valley Creeper = 698

Plan Length = ½ Span + Valley Correction – ½ Ridge

= 675 - (1.414 x -17.5 + 17.5) – 17.5


= 633 x 1.103

= 698


1.103

√2

0.466

1.489

1.000



Edge Bevel for Valley Creepers

What Triangle forms the Bevel

Crippled or Valley CreepersPlumb Cut


1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Crippled Centring Rafter













1000-675 = 325

Hips at 45°

½ Span Major – ½ Span Minor





Therefore where the Broken Hip intersects the Ridge Minor Span must be 325mm from the Centreline of the Ridge Major Span







1000-675 = 325

Both Hips at 45°

½ Span Major – ½ Span Minor



= (½ Major Span – ½ Minor Span) x 2

Or

= Major Span – Minor Span



This must be 2x

This



As the valley is at 45⁰ the intersection with the valley must be a further 325mm




Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major = 7641st Creeper Minor = 4061st Valley Creeper = 698Crippled Centring Rafter = 689

Plan Length = Major Span – Minor Span + Valley Correction – ½ Ridge

= 2000 – 1350 + (1.414 x -17.5 + 17.5) – 17.5


= 625 x 1.103

= 689


1.103

√2

0.466

1.489

1.000

Crippled Centring RafterPlumb Cut

• Crippled Centring Rafter is the same pitch as the Common Rafters.

• It must have the same Plumb Cut

1.103

√2

0.466

1.489

1.000Plumb Cut



Edge Bevel for Crippled Centring Rafter

What Triangle forms the Bevel

Simple Bevel Development

1. Plumb Bevel Rafter2. Level Bevel Rafter3. Edge Bevel Creeper4. Edge Bevel Purlin5. Plumb Bevel Hip6. Level Bevel Hip7. Edge Bevel Hip8. Face Bevel Purlin

From Previous



Every Valley Creeper must have an opposing creeper










From previous calculations we determined the following




Centreline length is the same as distance from the gathering point




To determine true length Long Pt

Centreline length 325

+/- Long Point Correction -7.5(-17.5 x 1.414 + 17.5)

Deduct ½ Ridge 17.5

Plan Length = 325 + -7.5 - 17.5


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major = 7641st Creeper Minor = 4061st Valley Creeper = 698Crippled Centring Rafter = 689Crippled Creeper Matching = 331

Plan Length = ½ Span Major – ½ Span Minor + Valley Correction – ½ Ridge

= 1000 – 675 + (1.414 x -17.5 + 17.5) – 17.5


= 300 x 1.103

= 331


1.103

√2

0.466

1.489

1.000

Crippled Matching RafterPlumb Cut

• Crippled Matching Rafter is the same pitch as the Common Rafters.

• It must have the same Plumb Cut

1.103

√2

0.466

1.489

1.000Plumb Cut


Determine Required LengthsCommon Rafter Major Span = 1084Common Rafter Minor Span = 725Rise Main Roof = 458Rise Minor Roof = 306Hip Length Major Span = 1.463Hip Length Minor Span = 9791st Creeper Major = 7641st Creeper Minor = 4061st Valley Creeper = 698Crippled Centring Rafter = 689Crippled Creeper Matching = 331 Creeper Shortening = 331

Rafter Spacing x Rafter Length / m

= 300 x 1.103

= 331


1.103

√2

0.466

1.489

1.000



As both spans are the same pitch they are SIMILAR so Creeper Shortening is the same for both spans

Roof Pitch = 25⁰



So the roofing members we have previously looked at are determined the same way


Roof Pitch = 25⁰




Edge Bevel for Crippled Centring Rafter

Edge Bevel for Crippled Centring Rafter is the CREEPER EDGE BEVEL

The same is for•Valley Creepers•Crippled Creepers



Edge Bevel for Crippled Centring Rafter is the CREEPER EDGE BEVEL

The same is for•Valley Creepers•Crippled Creepers

It follows that all the The purlin bevels are The same as the hip end



Determine Centreline Length Broken Hip



Broken Hip Run325 x 1.414 = 460

1.103

√2

0.466

1.489

1.000

Determine Plan Centreline Length = 325



Broken Hip Run325 x 1.414 = 460

1.103

√2

0.466

1.489

1.000

Determine Plan Centreline Length = 325

Centreline True Length

= Plan Length x Hip Rafter / m

= 325 x 1.489

= 484

Broken Hip Edge CorrectionAt Base

Broken Hip Edge CorrectionAt Base

Valley at Base of Broken Hip

Valley at Base of Broken Hip

Broken Hip Edge Correctionat Top

Broken Hip Edge Correctionat Top



Plumb cut is the same as the hipEdge Bevels are the same as the hip

1.103

√2

0.466

1.489

1.000



With the more complex roof a roof is. It is important to plan & determine as much of the roof offsite that you can

Documents

Broken Hip Roof. Lay out of Hip & Valley Roof Roof Pitch = 25⁰