Metal corrosion:
Some environments in New Zealand are quite corrosive to metals. Metal fixings used in exterior building applications are therefore required to be protected against premature failure by either hot dipped galvanising (HDG) or in more aggressive environments the use of stainless steel. You should consult your local council for advice on the appropriate type to use.
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For this example the deck shape determines the shape of the pergola
(see illustration 1).
Step 1:
To establish the pergola height, measure up from the deck for the position of the ribbon board and mark a level line. (See illustration 2) (Allow for rafters and battens)
Establish existing wall stud locations and mark on wall just below the ribbon board. Ensure you are fixing to the stud as the weatherboard alone is not strong enough to support the structure. Fixing the ribbon board to the fascia board is acceptable if there is sufficient depth below the gutter to allow adequate solid fixing.
Mark end positions of ribbon board on wall then measure ribbon board and cut to length. Place on wall and nail to fix at correct level and height.
Mark stud locations on ribbon board and drill for coach screw fixings @ 900 centres. (See illustration 3).
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Step 2:
Check top of 100 x 100 posts for the depth of beam with a 12mm deep seat. If the pergola is to be covered then remember to allow for adequate fall to ensure run off. Measure post length in the correct location, temporarily brace or have assistance, to plumb at the correct height. Mark bolt locations and drill for bolt connections (see illustration 4). Mark and drill bolt locations on the pergola posts and piles (see illustration 5)
Two other alternatives to this are:
A) Set the posts in a concrete foundation 350 x 350 x 450 deep (see illustration 6) - these posts could be part of the deck construction or freestanding but will require to be treated H5.
B) Use U-shaped post base brackets set in a concrete foundation where a concrete slab is planned (see illustration 7).
For pergolas that are to have a roof covering remember to allow for water run off. The check at the top of the posts will have to allow for the roof fall. Minimum fall is 50mm over 3m.
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Concrete Smarter
REMEMBER: outside drains only drain RAIN. If you are using cement or concrete around the home or at work never let concrete enter a stormwater drain. If you spill concrete slurry sweep it up with a broom (or wet vac) and avoid adding water. Dispose of left over or unused cement and concrete in a sealed rubbish bag – not in an open bin where rain could mean it leaks out and into a nearby drain. Remember to wash your tools on the grass (away from stormwater drains). Use sandbags to divert concrete wash water away from stormwater drains to an unsealed area.
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Step 3:
Measure the length of the 2 / 200 x 50 H3.2 beam; include the span between the posts plus the detail end lengths. Cut the detail shape to the ends of beam (see illustration 4). Raise beam up to sit on the cut seat at the top of the posts, drill for the 2 / 12mm diameter bolts to each post. Grease bolts, fix beams to posts.
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Step 4:
Measure and mark rafter locations @ 600 centres along the ribbon board and on the outside beam. Fix proprietary rafter hangers along the ribbon board (see illustration 3). |
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Step 5:
Select the rafter timber, measure and cut to correct length. This is the length from the house to the beam plus end detail overhang. Shape the end detail (see illustration 4). Offer up to rafter hanger locations and on the outside beam; securely fix (see illustration 8). |
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Step 6:
Cut to length 50 x 50 battens, lay on rafters in a selected pattern or to suit the chosen roof covering materials manufacturer’s specification. Lay on selected roof covering and fix down according to manufacturers specifications. |
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