A common question we receive from customers when adding the final roofing skin for their Pavilions is how to make sure the center of the roof does not leak?
When installing shingles for your Pavilion roof, whether a gable roof or an arching roof, you need to add a Ridge Shingle cap at the tallest point. You always put your roofing on from the bottom up. As both sides meet up at the top of the roof, add the Ridge Shingle caps along the top across the entire roof.
The Ridge Shingle caps look like this:
I have question about your Pergolas and the 2x6 rafter span which states they can go 20 feet with just 4 posts. While our design is closer to 14 feet (11 feet between posts) I am concerned with sagging of the 2x6s with such a large span. Coincidently I was reviewing a plan which is on the CA Redwood Assoc. website which has an example of an 8 x 12 Pergola (Windsor Shade Shelter) which recommends a 2 x 6 rafter span of no more than 6 feet. http://www.calredwood.org/pdf/Projects/Windsor+Shade+Shelter.pdf
Yes, if you are just stacking individual 2x6's, you cannot go anywhere near 20' in length. I think a 6' span as mentioned by the CA Redwood Association is a bit conservative, but I understand they don't want any unhappy customers.
The way we can do it and have been doing it for decades now is with extensive notching. When you notch all the timbers of a pergola into one another, they share the structural strength of the neighboring timbers. We do the notching in both directions and it achieves a multiplier effect in terms of structural strength. And, equally important really is that the notching locks the timbers in place so that even if one timber wanted to twist or sag - it cannot move. Lastly, you must use fully season lumber at 12% moisture content or less. You definitely will have movement issues if your lumber is green or semi-dry.
