by samanwita
Instructions
Things You’ll Need:
Check your site plan to ensure that there are no water, gas,
sewerage or drainage lines under your proposed pergola site –
you may need to mark their position before you dig footings.
Lay out your pergola using string lines. Check for square by
measuring the diagonals.
Dig post holes to allow at least a 300mm x 300mm x 450mm
concrete pad to be poured for the post stirrup bracket. For free standing pergolas, dig the holes a little larger to
accommodate a larger concrete pad for added stability.
Mix concrete according to the manufacturer’s instructions,
allowing a generous amount for each post hole. Pour concrete
into hole and set a stirrup bracket in the centre of the pad
allowing around 75mm clearance between the ground and the
bottom of the post.
Check the post is vertical using a spirit level or a post
level.
Temporarily brace the post and allow to set for 48
hours. Note: fast set concrete mix is available at your Magnet
Mart store, simply add water – sets in 15 minutes.
With the aid of a string line, trim the posts to the desired height.
Use the table below to calculate the length of rafters depending
on the desired angle of the roof.
Calculation Table – per 2 metres of chord length
Pitch Rise Rafter Additional Length
for every 450mm overhang
24 degree 460mm 1100mm Add 530mm
30 degree 600mm 1166mm 550mm
45 degree 1 metre 1414mm 640mm
NOTE: Add extra 150mm to total length to allow for angle cuts.
• The roof frame is constructed on the ground and erected as
a complete unit called a truss. Once you have constructed
the first truss you have a template for the remainder.
• Lay out the truss on a level surface commencing with the
bottom chord (the rafter of the traditional flat roof pergola
design). Mark the width of the pitched roof on the face of
the chord. Halve this measurement to find the centreline
and mark on the chord.
• Place the rafters on the chord so that they cross at the
centreline at the desired pitch (the angle of the roof). If the measurements on the chord are accurate, both
rafters will be the same length and will meet exactly in the
centre of the chord.
• Mark the point where the rafters cross each other and mark
the chord where the rafters cross it.
• Allow for overhang and mark the rafters accordingly. For ‘Pitched on Flat’ and ‘Saw Tooth’ roofs, mark the
rafter length level with the top of the chord.
• Cut the rafters and chord to length and use them as patterns
for the remaining trusses.
• Lay out the components for a truss, butting them together
firmly and gang nailing on both sides.
Commence with an end truss and temporarily nail a length of
timber to the mid point of a rafter and the centre of the chord
With help from an assistant, lift the truss into position on the
pergola frame, nailing the timber brace to a post,
check that the truss is correctly positioned and plumb.
Nail the truss to the beam with joist straps at each end. Repeat this
process at the other end of the roof, when the end trusses are
secure, nail a batten to them about 50mm down from the top on
each side of the apex.
Fix the remaining trusses evenly between the two ends, securely
nailing them to the beams and battens. Remove the temporary
braces from each end truss and fit battens across the trusses at
around 400mm centres.
A wide range of timber finishes is available at Magnet Mart to protect
your pergola, come on in and talk to one of our helpful Associates
about your needs.Tips & Warnings
How to Build a Pitch Roof | Provided by eHow.com
