Simpson Post Base Selection

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Old 05-18-16, 02:36 PM
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Simpson Post Base Selection

I'm doing a plan for a free-standing patio cover and looking at Simpson post bases. The structure will be 12'x15', with 8x8 DF #2 posts (columns) and 8x10 DF #2 beams. I am going the use knee braces in both directions on all 4 posts for lateral stability. I've read just about everything on the Strongtie website and also read a few threads about this. I know some people like to use the embedded type (CB, CBSQ, or CCSQ) but I was favoring the ABU so I don't have to trust the concrete guys to get the placement exactly right. With the ABU I can install them myself so I will get the placement right. I have read that some like the embedded ones because they say it will resist rotation more, but as Simpson points out on the website, you should not rely on the post base for resisting rotation. I would think that as long as the uplift and load capacity is enough, since I'm using full knee bracing in both directions, any post base's limited ability to resist rotation is pretty-much irrelevant.

BTW, I would be installing the ABU88 with 2 Simpson 5⁄8"x6" Wedge-All anchor bolts as specified by Simpson.


So, what's the real story here? Opinions, favorites, rants, raves?
 
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Old 05-18-16, 02:52 PM
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ABU is fine. You don't worry about twist, you worry about lateral movement, which will be at bay with the 5/8" bolts. I prefer the ABU's for the same reason. 8" lumber is massive for such a small deck, but it will make a statement, for sure
 
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Old 05-18-16, 03:13 PM
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Thanks Chandler. I know I could go with 6x, but I'm going for the heavy timber look. And, my beam span is 12' and don't want ANY noticeable sag. I've attached a pic of a pergola that is a very similar structure, but mine would have a metal roof. I'd have the guy who built this pergola come and built my patio cover too but he's is out in California.

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Old 05-18-16, 03:27 PM
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OK, now the post-beam connection.

I was going to start another thread regarding the post-beam connection, but since the pic I posted relates to my question I'm going to ask it now. I see various post-beam connectors from Simpson, but I think the t-straps as used in the structure in the pic are the most attractive for this sort of design. However, it seems to me that the t-straps would make for a less rigid connection than a Simpson CC or CCQ. I notice that their PCZ has pretty good specs too, and has a lateral rating as well. And, I have seen many cities in earthquake country show t-straps as an option for patio covers, so I'm confused but maybe I'm missing something here. I've even seen t-straps used in non-braced structures, so I have to ask, "what's up with that?". If I went with a t-strap, I'd be looking using at the Simpson 1212HT or 1616HT.
 
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Old 05-18-16, 06:09 PM
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Are you going to brace your deck as shown on the pergola with angles? If so, you may can install a 1" dowel on top of your posts with coordinating hole in the beam, then install your t braces. I think the t braces will look so much better than anything Simpson will have. I would not, however, use decorative ones. I would move up to 1/4" steel. You may need to have the custom made, but lagging them in the beam and post would be rock.

No, don't start another thread. We read them all anyway.
 
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Old 05-18-16, 10:14 PM
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Thanks again Chandler. The heaviest t-straps Simpson has are the 1616HT which are 7 gauge (3/16") so I guess I could get some 1/4" made up. I hadn't thought of the dowel through the top. I know some guys will put in a couple of 1/2" lag screws in through the top, countersunk into the top a bit.

Check out this pic of my neighbor's patio cover. I talked to him when he was building it. The beam and columns are 16"x16" green Ponderosa Pine, with the beam 20' long. He had to hire a crane to place the beam. The rafters, which you can't really see, are 6"x8". There's no knee bracing since it's not freestanding and he has about 18" of ledger along the house. He had the L-straps made up. I think I would have done the straps made differently, so that 3 lags went into the beam and 3 into the column (and not so close to the end of the column).
 
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Old 05-18-16, 10:40 PM
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T-plate

I like this one. 1/4" steel. Sold by timberplates dot com.

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Old 05-19-16, 04:32 AM
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I like that hole arrangement, too. More meat for connectors. Driving fasteners from the top will first, require long fasteners, and second will create a hole for water to bypass directly into your post grain. I would avoid it if possible. Allow water to naturally shed would be best.
 
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Old 05-19-16, 03:11 PM
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Dowel questions

I'm thinking about the dowel idea. I understand now that the dowel would be between the mating surfaces only and would not come to the top of the beam. Wood or metal dowel?

I think I would need to get the alignment of the dowel holes exactly right or I wouldn't be able to square up the beam on the column.
 
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Old 05-19-16, 11:23 PM
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I found a picture that might be closer to what I want to build. I'll tell you why I like the design in this picture. We have what may seem like an odd building requirement here in Albuquerque. Any shade structure that is closer than 10 feet to the house must be attached, though the code enforcement guys tell me the attachment can be almost anything as long as it's attached at 2 points. I'm not sure why they have this requirement, except maybe they think that if it's attached then it can't fall over on the house? One of the city code guys also suggested that I make it self-supporting so I don't have to get an engineering report showing the vertical load capacity of the house structure and footings. So, I'm thinking, why not use these the required attachments for lateral support, eliminating the need for the braces perpendicular to the house. I also think this would eliminate the need for the braces parallel to the house on the inner beam. I would still use the braces parallel to the house on the outer beam for the lateral forces generated by wind. Now, the picture below seems to show just what I'm thinking. Of course mine would be on a slab and not on a deck as in the photo, and I would size the knee braces smaller than those HUGE ones. I would also put the inner beam closer to the house (maybe 2 feet) so there's no significant vertical load on the house at the attachments. So, now I have more questions:

1. What do you think of this design in general?

2. What do you think about the angle plates they used on the post-beam connection? I like them and Simpson has a very similar product (HL55 or HL76). I'm curious why I don't see my pictures with these used.

3. It has occurred to me that instead of just 2 attachments I could put a ledger on the house and use hangers for all the rafters. Maybe that is what is in the picture but it's too dark to see under there. What do you think of that idea?
 
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Old 05-20-16, 03:20 AM
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Yeah, your dowel placement will be a trick. Wood or metal (galvanized), either one would work.

1) I like the design. Obviously not built for snow load, nor extreme drainage. I would question the flatness and the flashing method. I feel this one is not attached via a ledger mainly for that reason.

2)I like the use of massive painted steel plates in this type construction.

3) Again, I don't think it is attached due to the flatness of the roof. I am not sure, but "attaching" it to the house by rudimentary means according to the inspectors may cover the loophole with insurance coverage, meaning an attached portion is covered where one that is not attached may need separate coverage.
 
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Old 05-20-16, 11:19 AM
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Thanks for your input Chandler.

I like the angles but I'm a little hesitant to use them simply because I have searched extensively and could only find that one picture of them in an actual structure. I understand that given the use of the knee braces, the angle really only serves to hold the beam down and position the top of the column on the beam (lateral). But still, I am troubled by the scarcity of examples of their use. I would think that if this is a good idea, it wouldn't be so difficult to find it actually used.

The t-strap, on the other hand, seems to be used extensively. However, I'm not totally comfortable with the t-strap either, even with a knee brace, since it seems like the t-strap really won't keep the top of the column positioned on the beam (laterally) like the angles would. I hope that makes sense.

Not being a structural engineer or builder, I'd like to go with what is conventional.

Hey, maybe I could use the t-strap AND the angles! In that case maybe I would just use a smaller angle. Hmm.
 
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