Pergola construction questions

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Old 02-25-16, 11:57 AM
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Pergola construction questions

Hey everybody,
I'm going to build a pergola in my backyard which will go over the paver patio which is being built this spring.

I've included a pic from the google sketchup that I've made and a photo of a pergola which is my inspiration.

Outdoor-Canopy-and-Pergola-by-Corradi-Photo-1.jpg Photo by JPDSODPB | Photobucket

Little bit of background. The paver patio is slated to go in at the end of march. Once they dig down for the patio I'm going to have them dig the holes for the 6 posts that I need.
I'm going to use 6x6 pressure treated wood for the posts with the bottom wrapped in vycor.
Few inches of gravel, Post then a couple more inches of gravel. Concrete and will slope the concrete away from the post.
Once the concrete is cured, they will put in the gravel and sand for the pavers and finish the patio.

The wood for the pergola is going to be Western Red Cedar and I'm planning on wrapping the PT Posts with 1x6s. The beams are going to be 6x6 which will be notched so they rest on the beams. The largest span is going to be 15' which is longer than recommended but I'm using a single 6x8 piece for each beam the whole 20' length of the pergola, one post is 5' left of center. Considering I'm doing roman shade for the top, I shouldn't have a weight problem.

Here are my questions.
1. Do you think I should wait to wrap the PT beams for a couple years so they fully dry out? I've heard that PT does warp over time and I might have gaps on the beams if I put up the 1x6s too early.
2. I'm going to do cutouts for the Beams/posts so the beams rest on the posts. My only concern is the corners. I've included a drawing of what the post will look like before I place the beams on top of them. There will be a 3x3 square which is left of the 6x6 post. Will this not be strong enough for the lateral forces on the pergola?
3. This design doesn't have any cantilever on the beams which might be a problem. I've looked online for any information about beams without cantilevers causing more sag but couldn't find anything. Will the no cantilever be a problem?
4. Is this overkill by using 6x6 for the posts and 6x8s for the beams?

Thanks
Rob
 
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Old 02-25-16, 01:27 PM
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Where are you located? There are specific/specialized considerations with some regions.

What is the concrete you mention? Are you pouring a concrete slab over the whole area and then base and sand for your pavers or are you pouring a concrete ring around the top of the post holes?
 
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Old 02-25-16, 07:13 PM
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What is the concrete you mention?
OP wants to set the 6 x 6 posts in concrete.

I would recommend setting the posts on footings, using stand off post bases.
 
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Old 02-26-16, 04:58 AM
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Have you consider using cedar posts? That eliminates the need to wrap them along with any issues with the miter joints opening up with weather/humidity changes. I agree the post should not be embedded in concrete.
 
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Old 02-26-16, 08:01 AM
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This is what I was questioning "...Few inches of gravel, Post then a couple more inches of gravel. Concrete and will slope the concrete away from the post." I not certain if they are just doing a ring of concrete around the top of the posts.

And, the OP mentioned that they will be using Cedar posts. I assume they will be wrapping them for cosmetic reasons.
 
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Old 02-26-16, 08:38 AM
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I'm going to use 6x6 pressure treated wood for the posts ..... and I'm planning on wrapping the PT Posts with 1x6s.
..........................
 
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Old 02-26-16, 08:59 AM
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Answers

Sorry I was having issues with access, had to reset my login.

I'm in the Northeast US (Long Island, New York)

My plan for the posts was the following in detail:
Dig my 6 post holes, 45" deep by 12" round (Frost line here is 42")
Fill the bottom 3" of gravel"
Wrap Pressure treated 6x6 with Vycor quite high (Probably 4 feet up).
Put post in hole and fill with another couple inches of gravel.
Fill hole with concrete, plumb/anchor the posts.

I was not planning on doing concrete slab and using anchors. My concern with that is the lateral force that would be on these. Its going to be quite heavy as my beams are 6x8s and we do have some strong winds from time to time.

The reason using pressure treated posts and wrapping them is from the ground contact. If I use Cedar posts and wrap them in vycor, it probably won't last more then 10 years.

I don't mind leaving the PT Posts exposed for a couple years until they fully dry out so when I wrap them it will last a while.

Do folks think there isn't any concern with lateral forces?
 
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Old 02-26-16, 11:18 AM
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No, you are correct to be concerned about the lateral forces. I like the post brackets when there will be support from above like diagonal bracing. If you are going for a clean looking post and beam without bracing then the posts do need to get much of their lateral support from the ground.

With most soils I simply back fill around posts with compacted crushed stone. I put a few inches of stone down the hole around the post then use a long 2x4 as a tamper to compact the stone. Then keep repeating until the hole is filled. Very quickly it grabs the post rock solid and there is no waiting or bracing required while concrete cures.
 
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