Pergola Project

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Established Member
5 Apr 2010
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Going to be building a Pergola .. welcome a sanity check on my ideas. Pergola will lead up onto a deck area, length of Pergola run will be around 7.2m ... (ideally 3m wide)

Which will be created by a run consisting of 4 ‘bays’ between each 100 x100 upright. Bolted to cast-in concrete supports – had these custom made in 6mm plates and galvanized -

The Pergola will have 4 bays - each bay looking a bit like

Assuming I use 150 x 50 for horizontal beam pairs, which will be through bolted to the 1`00 x 100 posts ... and 150 x 50 for the cross rafters with 100 x 50 for decorative longitudinal infill’s ...

First Q ... What is the max span practical width of the walk through .... I would like to have at least 3m width of walkthrough ... with bolted pairs of 150 x 50 ... making effective 150 x 100 beam ..supporting the 150 x 50 rafters it seems to me that 3m span would be OK ?
General construction will be as in...

Second Q is what is Max spacing between each ‘bay’ ... ideally I’d like bay to be 1.8m between posts ... giving overall length of 7.2m
The ‘far end’ of Pergola will be built into a roofed area over one half of a deck ... so extra rigidity provided there.

Also any thoughts on spacing of the rafters ? if each bay is 1.8m long I could use pairs of rafters either side of each post ,,, and a separate pair mid way along span ... as per sketch ..

Might be better than just simply regular spacing of them.

The longitudinal in-fill will be 100 x 50 ... and although will provide some rigidity ... mainly just decorative.

Comments ? suggestions ? ... eg should I add gallows brackets at start bay

Sorry about all the link ... but seemed easiest way to describe

Rob Platt

Established Member
21 Nov 2010
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i cant see any problems with any of your sizes 150x50 will span 3m without any load on it without any problems. it may given long enough slowly deflect under its own weight but this will be insignificant i wouldn`t bother with gallows brackets. 1.8m is not a problem either.
all the best

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