# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  pergola post heights for pitch

## Yeeha88

hey all so im going to give building my pergola a crack this month. its a fly over design and just wondering with the pitch i need 5° per metre. the roof itself is 5.5m projection so i understand thats 192mm fall. however theres 400mm overhang at the back from beam and 600mm overhang at the front from the beam. so question is whatever height my roof extenda brackets are do i subtract 192mm from that datum for my front post heights? if that makes sense

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## droog

Depends on the reference points.
Is the 192mm is based on 5.5m and are your support point 5.5m? Ie between your extenda brackets and the front post. 
If the 5.5m is the length of the roof then to work out the difference in support locations is :
5500 / 192 =X
Distance between extenda and from post x X 
Although unless there is significant difference between the roof length and support locations it is only going to be fractions of a degree. 
The blocklayer website may assist. https://www.blocklayer.com/

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## Yeeha88

hey mate yeah based in the 5.5 roof. so distance from extendas to posts would be 4.5. taking out overhangs

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## Yeeha88

so 157mm around there should be fine?

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## droog

Sorry got it a&$# about   
192 / 5500 = 0.035
0.035 x 4500 = 157 mm 
If the roof length is 5.5m and you want 192 mm fall over the roof, and your support points for the roof are 4.5m apart then the height difference between the support point will need to be 157mm.

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## Yeeha88

yes thank you clear things up sometimes i overthink haha

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