Pergola Problems

You should be able to lap the plexi under the shingles at the top. You might have to add some flashing and the sides could be done with a barge rafter type set up with a fascia board. Putting a 1 x ? on edge cut on an angle from nothing to the major neight you could seal the sides. The plexi could be screwed down with rubber washer screws, just don't put too many in or too tight.Finish tightening the screws at the end with a screwdriver, not a screwgun to make sure not to blow out the washers or crack the plexi. A dab of clear silicone on the screwheads for extra measure wouldn't hurt. Make sure that the plexi or the flashing goes high enough under the shingles to get above the rain ways(slots in the shingles). If you have to have joints in the plexi make sure they are not crosswise and you can leave about 1/8" gap between the pieces and put an aluminum strip over the seam after a good bead of silicone, For the seams use small wood screws counter sunk to hold the plexi edges then rubber washer screws on the covering strip, Overhang the plexi about 2" on the sides and bottom edge so runoff doesn't run back to leak or damage the wood edges. Hope this helps.

Thanks for the response. If I understand correctly, the method you suggest will see a stepped roof with the existing roof overlapping the pergola roof to close the gap then the pergola roof would start stepped down fronm the extended house roof ?

The first way creats a step. the extension would creat a v. L or \_

Try adding to the eve of the roof to drop it down to the needed hight to connect the roof of the pergola. then glass the top. Another option is to extend the roof to the pergola to create the seam. Both can look nice and work. The former being the cheaper but if done right can add caricature with a decorative trim.

We would call the roof type a "shed" and it creates a transition. As long as the flashing starts above the transition there shouldn't be any problem and the elongated triangle fascia boards on the side can be sealed to the original roof surface with silicone or blackjack and the apearance is entirely dependant on the care you put into the application. If you look around there are roofs done just like that all over as it's probably the easiest way roof an addition

Not knowing where you live I don't know what the weather is like.

You state that the pergola wasn't originally designed for a roof.

So you have a few other issues to think about.

If you get snow, are you sure your pergola is built strong enough to handle snow accumulation after you add the roofing. Most pergolas I've seen have almost no slope whats so ever. Snow & ice will accumulate quite fast with almost no run off.

Rain & wind loads are other factors you may want to think about. Once you put a roof on it the wind may get under it and try to lift the whole thing up.

You also may need a permit to add a roof depending on your municipality.

Thanks, I've considered all the variables that you have mentioned. I built it, it will hold the snow. When I originally built it there was not going to be a roof. Had I some forsight I would have adjusted the pitch to match closer to that of the roof.

At this point you can still adjust the pitch and or adjust the structure; in effect, to realign the pergola to the existing roof line.

Example:

Remove gutter and facia of existing structure, shorten outboard upright posts and extend inboard posts. Join pergola rafter to existing rafter extensions and/or fasten to exterior wall with plates/brackets check local codes.

bwise

Another answer would be to talk with a canvas and vinyl awning manufacturer, I have done applications like this in the past with a aluminum frame and vinyl material to achieve a very nice look, the spacing on your joists (?) on the pergola may have to be somewhat closer together to support plexi.

Thanks, I like the way you think. I'm considering a retractable awning, it would need to be 14 feet by 7 feet; ever come across a beast like that? The more I think about plexi and the proliferation of pine trees it would be a mess after one season.

www.sunsetter.com/moterized_awning_new.asp

You have had some good answers, but before you do anything ask yourself the question :- when it rains and blows, which direction does it come from generally speaking? because you may want to make sure that under extreme conditions, the rain does not get blown into any gaps.....

Here the bad weather comes mainly from between SW and NW......but I am mainland Europe!!! That is normal for us.....we build roofs to make sure that water is generally not blown in anywhere by westerly winds and thats our weather angle!!.....

Good point

without knowing the run to rise it is going to be a problem with keepting the plexi on the safters. as the pictures show. andy points out it looks like you will have a real problem with wind lift. best check your county codes office for going any furhter with that idea.

'da ber