How far a span can I build a Pergola over?
 

We'd like to put a pergola over part of the pool area for some shade but the span it would need to cross is 30ft (ish). How can I do this without putting posts in between? It may be unavoidable but I'm starting my research on it. Thanks

There is no real loading on a pergola, so that makes it easier. But 30 feet is not an insignificant distance. Are you willing to have structure to support it on both sides? It's possible to lend support from above with tension cables if you extend the supporting posts on the sides above the pergola height.

Are you planning to use solid lumber, laminated beams or I-beams?
Good luck finding solid lumber in 30' lengths. Laminated beam or I-beam - no problem. Do you want 18 inch high support beams though?

Not sure where you’re located or what time of day you’re typically using the pool but depending on the above you could construct it at an angle so that it casts a shadow without spanning the pool.

It wouldn’t fully block the sun but provide a dappled effect.

what is max. wind loading in Omaha?

you may want to look at glue-lam

there are some new wood products in Orygun that they are using to build 4-5 story buildings from; maybe in demo stage

i just did some rough numbers.

30 foot span. simply supported at the ends. a 250 lb man can do a chin up in the middle and deflect a 4x12 beam 0.48 inch. i think the code allows 1/360 deflection. (?)
i dont know how deep this thing will be so i couldnt add the weight of the pergola slats.

Might want to go with welded and sealed end boxed (or I-beam) metal instead of wood.
Welded and sealed with seriously heavy duty paint.
Braces on corners.

No guarantee on rust in ten years.

Cables and canvas.

Probably knee braces, at the very least (assuming posts/support on either side).

Good call. Forgot about those. There are several pre-fab metal-beam/frame pergola kits out there (still using wood slats/ribs). Usually with heavy-duty/weatherproof coatings/paint.

Sun Sail?

Keep in mind the sun warms the pool. Cover it and you'll drop 5-10 degrees plus.

Just changing our plaster from white to grey raised our pool a few degrees.

Damn, nice to have Vash around.

Anything that catches wind...

Just to give you a bit of reference. I am building a 24' (with 3' over hang on both side) second story deck. My engineer called out for 7.0' x 11.85" Parallam. I am debating on getting Alaskan glue lam for wet areas ( It never rains in socal but when it does, I not a happy camper). I can't get Parallam Plus plus here on the west coast or socal so am beating my head against the wall because that big ALaskan beam is 1400 bucks.

maybe a couple of these instead

http://forums.pelicanparts.com/uploa...1588718853.jpg

Cantilevered stuff looks great. Wind could be a deal breaker.

This gets my vote. The welded triangular steel truss/beams or whatever won't look nearly as heavy as wood beams and more light gets through.

^^$$$ probably.

Is snow load a consideration in Omaha????

Around here, our county Building Dept would be your best source of info.......

Snow can’t build up on pergola, can it? I don’t think you even have to account for any live loads (people).

Snow builds up on my pergola, which is covered by an American Wisteria. The damn thing grows so fast if you're not careful, it'll grab you as you walk by. It's always trying to get into my house, too.

thanks for all the responses. I'm not an engineer but have a math degree so not afraid of doing some calculations. Wind and snow are a factor here for sure--40-50mph gusts are fairly common on windy days so some type of sail is a consideration but I have to be able to remove it easily. The pergola will just shade one side of the cement deck to the North of the pool so it wont affect the pool temps. I'm looking at some of the DIY canvas shade curtains that are easily deployed/removed. We've also got a large weighted umbrella that is portable but a permanent solution would be nice.

roller furling is eazy to do with cloth

pvc pipe over a cable/rope to roll up on by the house

simple drum and rope to pull on to roll it up

or just buy an awing pre made like sunsetter brand ads

snow loads ? why have it up in winter

Dude how big is your pool?!!

pool is 20x40 with 5ft walkway around 3 sides and a larger pad on the 4th side (this is the area I'd like some shade on). I'm guessing I'll need some type of truss design to make the span. Researching truss design now.