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Forum topic by handofdoom posted 03-01-2010 07:09 AM 1045 views 0 times favorited 7 replies Add to Favorites Watch
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handofdoom

6 posts in 2472 days


03-01-2010 07:09 AM

Topic tags/keywords: redwood pergola help patio covers wood concrete post beams

Im building said pergola in my yard, and need some help with the spans.over all its 18’ x 16’ , back part of pergola sits on top of block wall and front part rest on a redwood beam 4×6 or 4×8, post will be 4×6s about 14’ apart, joist are 2×6s 20” apart with 2×4s on top, bypassing city so cant go there for advise. Is 4×6 beam 18’ long on top of 2 post 14’ apart gonna hold up the 2×6s and 2×4s. HELP is this thing gonna come crashing down on me. gonna cement the post in concrete 30” of concrete.

18'x16' redwood pergola

-- Before you criticize someone, you should walk a mile in their shoes..... .....That way, when you criticize them, you're a mile away and you have their shoes!


7 replies so far

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handofdoom

6 posts in 2472 days


#1 posted 03-01-2010 07:44 AM

my pics didnt show up in my post so im trying again.

Photobucket

18'x16' pergola

-- Before you criticize someone, you should walk a mile in their shoes..... .....That way, when you criticize them, you're a mile away and you have their shoes!

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shopdog

576 posts in 2946 days


#2 posted 03-01-2010 02:30 PM

It depends on the condition of the 4×6. A bad knot in the wrong place could be a problem. Also, is there ever going to be a snow load on top?
I build pergolas as part of my business, and I like to use doubled 2×10s for that beam. I wrap them around the post, and double bolt with 1/2” bolts.

-- Steve-- http://www.urbanexteriors.biz

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SKFrog16

661 posts in 2661 days


#3 posted 03-01-2010 05:33 PM

I agree with shopdog but would also like to know what you are doing at the back wall!! Is this facing into the prevailing wind? Are the rear supports just resting on the wall? How are you going to address twisting of the rafters without cross blocking? How long is the cantilevered front?(not visible in drawing).

-- Methods are many,Principles are few.Methods change often,Principles never do.

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handofdoom

6 posts in 2472 days


#4 posted 03-02-2010 05:04 AM

the back wall has 5 anchor bolts and i live in los angeles so no snow and little wind to worry about. the front cantilevers about 4’ and the lumbers gonna be construction all heart redwood.18'x16' pergola

-- Before you criticize someone, you should walk a mile in their shoes..... .....That way, when you criticize them, you're a mile away and you have their shoes!

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Dark_Lightning

2632 posts in 2570 days


#5 posted 03-02-2010 05:14 AM

Drop by the City Engineer’s office and ask for a Form V- it’s free. You do not have to commit to anything there, and they’ll even give you pointers. For LA, I’m not sure you have the right sizing. The new earthquake codes are much more stringent than you might believe. I’ve skated around the Building Code in the past, but it was more the letter of the law than the actuality. For instance, I had to have a handrail above my retaining wall when I terraced my back yard for a shed, if it exceeded 36 inches. So I poured the footing and slab 3-5/8 inches (2X4 width) above grade, for a total of 33 inches. Harrrr

Oh, is the base for your posts 30 inches by 30 inches? Another size issue that can be resolved by picking up that Form V. I think I downloaded mine, many moons ago…though I don’t even live in Los Angeles County any more.

-- Random Orbital Nailer

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handofdoom

6 posts in 2472 days


#6 posted 03-02-2010 05:39 AM

the post will be set in concrete 30” deep and 14” wide,the post are all heart redwood (measure 3times cut once post alone cost $50 and 1600$ in redwood lumber).

-- Before you criticize someone, you should walk a mile in their shoes..... .....That way, when you criticize them, you're a mile away and you have their shoes!

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jayjay

639 posts in 2507 days


#7 posted 03-02-2010 06:07 AM

I built a redwood pergola for my back patio about 6 years ago. It measures 16’ x 32’. I used 4×8 pressure treated lumber for the posts, which I then wrapped with cedar. 6 of them spaced out about 14’, two rows of 3 basically. For the cross beams, I doubled up 2 ea 2×8’s to span between each post, and bolted it with 2, 1/2 bolts on either end. For the joists, I used 2×8’s every 24” or so. On the very top, I used 2×2’s spaced every 2”. When I originally drew up my plans, I was going to use 2×6’s, but I spoke with a building inspector, and he told me that because of the spans I was using between my cross beams, 2×8’s needed to be used instead of 2×6’s. It cost a bit more, but in the long run, I think it really made for a much sturdier build.

-- ~Jason~ , Albuquerque NM

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