# What size timber is used for roof trusses?

## What size timber is used for roof trusses?

We usually opt for the 35mm thickness in timber when designing standard timber roof trusses. This could be for Fink Trusses in a house construction or Queenpost trusses for a garage. Meanwhile, the 46mm thickness option is used for attic trusses due to fire regulation guidelines.

## How do you calculate timber for trusses?

Truss count = ((roof length * 12) / 24) + 1 The simplest form of this equation is to take the length of your roof and divide it by 2. For example, if your roof is 40-feet long, it will need a total of 20 trusses.

**What is the maximum span for roof trusses in meters?**

The new regulations have simple line drawings for: Four-bay Howe truss with a maximum clear span of 6 m (the same as centre right above) Six-bay Howe truss with a maximum clear span of 8 m (called a King Post Truss above)

**What is the spacing for roof trusses?**

Roof trusses should be 24” apart, on center. Trusses are allowed to be closer together, at either 12” or 16” on center, but building codes allow for 24” on center spacing without using heavier duty fasteners for truss to wall connections.

### Why is timber used for roofing?

The popularity of timber as a roofing material is because it has been hitherto widely available, is generally light and easy to work with, has an excellent strength-to-weight ratio, can be an economic choice, usually has pleasing looks and can be an environmentally-friendly option when sustainably sourced.

### How do you calculate span of a roof?

Calculation set out

- Rafter run = external width between the wall plates divided by two.
- Rafter span = rafter run divided by cos °.
- Overhang = eaves width divided by cos ° (add dimensions for brick veneer).
- Ridge strut = rafter run times tan °.
- Decide whether an underpurlin is needed; if it is place it at mid-span.

**What is the spacing of roof trusses?**

**What is the standard distance between roof trusses?**

#### What is the distance between purlins?

The maximum distance between purlins is five (5) feet on center. If your building site is in a region that is prone to heavy snow loads or high winds, then we may place your purlins closer together for added strength.

#### What are the steps to building a roof?

10 Steps to Building a Roof

- Tear off the old roof.
- Install the drip edge.
- Roll out the underlayment.
- Cover the roof with felt paper.
- Waterproof the valleys.
- Apply starter shingles.
- Install the shingles.
- Install the flashing.

**What size are roof joists?**

Wherever possible, joists should span the shortest distance. Common joists sizes are 200 x 50mm, 175 x 50mm, and 150 x 50mm.

**How do you calculate roof beam size?**

How to Size a Beam to Hold a Porch Roof

- Determine the load per square foot that the roof must support.
- Multiply the load per square foot by the total area of the roof.
- Divide the total load according to how many supporting beams the roof will have.
- Write down the beam strength formula: Total load in pounds = FBd^2 / 9L.

## What is the minimum spacing of purlins?

In order for the sheets to be easily fixed to the purlins, as a rough guide they should be at least 50mm wide. When positioned, roof purlins should be spaced no further than 1.2 metres apart when using sheeting with a thickness of 0.7mm, and 1 metre when using 0.5mm sheeting.

## What is the size of purlins?

Purlins are typically anywhere from 4” up to 12” with a flange width of 1-½” up to 4”. They are available in a variety of custom sizes and lengths depending upon what a project requires.