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crypterman 09-24-2012 03:05 PM

post & beam deck construction question
I am building a deck where my beam for the joists will rest on top of a 6x6 posts or post and beam construction.

I do not want posts every 8 or 10 feet because it will take away from my downstairs view. I understand when doing post and beam that at least one beam should span the top of the post to the next post so that not all the beams should end and begin on top of a post and that any joining be done over beams

Is this correct should I NOT end and begin my beams on top of a post. If that is correct then without ready treated lumber over 16ft posts are going to have to be every 8 feet.

How do I spread my posts out wider

GBrackins 09-24-2012 03:28 PM

if you want to span a distance greater than allowed by the use of 2x12 pressure treated wood you could use one of the following:

1. steel beam
2. treated parallam beam

just to give you some information this link will provide you with the American Wood Council's "Prescriptive Residential Wood Deck Construction Guide." It is based upon the requirements of the 2009 International Residential Code, basis for most local and state building codes

it will provide the span of commonly used wood species for beams based upon the size of the deck.

Hope this helps

notmrjohn 09-24-2012 04:13 PM

If I understand "... at least one beam should span the top of the post to the next post so that not all the beams should end and begin on top of a post and that any joining be done over beams," you mean you want to sister 2x beams to get longer span between posts and make longer beams then only one joint of the sisters should be on a post, the joint in other sister should rest on another post, and not next one in row. All beams should end and start on a post. Adjacent beams should not have joints on same row of posts.

I do not understand " any joining be done over beams." If your joists rest on beams their joints should be over beam and should be sistered both sides a foot each side of beam or at least lap jointed same distance.

Generally speaking, a site built sistered beam is not going to be as strong and not span as far as factory built engineered beam. A steel flitch plate ( sometimes pronounced fish plate) sistered and bolted between 2X will give more span, but add lots of weight.

And considering that weight, longer spans mean more weight on each post. You will want to have deeper and larger diameter footings and larger posts. 6x6 is minimum for second story deck with normal spans.

I don't know size of the deck, or span you want, spacing or depth of beams or weight of them weight could be considerable. Just judging from your question, and not being judgmental ( Now that was confusing) or based on my understanding of questions, in which case I am being judgmental, I do not think you have experience to engineer this yourself, even with all the expert advice from perfect strangers you will get here (though you could post plan), online tables or free pamphlet from HD. If 'twere me I'd call in structural engineer.

Rocket98 09-24-2012 04:16 PM

You need to find out what type of load you have berring on the wall that are building. You can splice the beams on top of your posts with a post to beam connector. I would look to glu-lams. They are made in 5 1/8" widths. You could then furr them out to your wall size with 3/4" plywood furring. Hope this helps.

Daniel Holzman 09-24-2012 05:57 PM

GBrackins has given you the link to the standard guide for constructing a deck. The guide discusses in considerable detail exactly how to construct a beam, the allowable span for beams of different materials and sizes, where to make the splices in the individual lumber making up the beam, how to attach the beam to posts, minimum post size, required bolting pattern, and a lot of additional information. You should also discuss your project with the local building inspector prior to construction, as there may be local regulations, or your area may operate under a different code.

If you elect to construct using material not specified in the standard guide, typically you are going to need an engineered plan (a plan prepared by a registered professional engineer or architect) to get a permit, since you will not be designing strictly to code. This is fine, it is almost always permissible to deviate from code if you get professional design advice. This would apply if you choose to use laminated lumber, steel, aluminum, or any other material not discussed in the code. Unless you do not need a permit to build (this is still the case in some areas), in which case you have flexibility to construct based on your own design method.

Davejss 09-24-2012 07:29 PM

What are the dimensions of your deck? Can you post a pic of your plan?

mae-ling 09-24-2012 08:20 PM

How far aprt do you want the posts, size of deck, location, etc. all come into play.

Sounds like you are going to have to get an engineered solution.

peakcelln 10-04-2012 05:11 PM

You could also try a Box beam built out of 6" steel studs and track. You can get them up to 24' long at HD and then cut them to size. The two studs get screwed together(Back to Back) and the track fit over the top and bottom. Use a good #10 3/4" Tek screw to attach all pieces every 8". You can have it powder coated prior, or just get some good steel paint if its gonna show. I did this myself and it was easy AND inexpensive. You'll also find the lower in gauge you go in the track and stud, the longer the span can be. Steel is obviously straight and true, so no need to worry about warped wood, now or in the future. Hope this helps.

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