Building a wooden carport, free standing, plan on using 4 x 4 for the posts. Cement slab is 10 x 20 with posts at 10 foot spacing.

Trying to determine the "smallest" size douglas fir to use for the beams. There isn't going to be any larger span than 10 feet involved in either direction (center posts at 10 foot). The only thing that is going to be going on it for a roof is some type of shade cloth or at the very most latice.

I had figured on using 2 x 8's for the perimeter beams, bolted to the posts. Running 2 x 6's for the rafters, on 16" centers, on hangers. With supports at each post. This all seems good enough for me.

Please don't tell me to go see the building committee about this, I already know that. The diagrams I have gotten from the city show the use of 4X lumber for the beams...just think this is a bit overkill in this case. I am just trying to find the chart to use for span and weight requirements.

If you can give me some information on this, it would be appreciated.

 

You are limiting your reponses since you infer you do not care about doing it to the minimum accepable standard.

Code also apply to how you put it together. What you going to do to give it lateral strength for the next earthquake or do you plan on letting it drop on whatever (a person or maybe a car that costs more than the temporary carport?).

Maybe you should take the time to find out what is really required? - OH - I see you do know what you should do.

Most DIYers want to do it right and save the labor cost instead of doing it cheap at any cost.

Dick

 

I will try to clear up a couple of things.

The sheets of paper I got from the city leave a lot to be desired. The opening sentence states, "This information summarizes certain portins of the Uniform Building Code....Where the details provided here cannot be followed or where other choices are desired, the U.B.C should be consulted."

So when they "suggest" that a 4 X 10 beam be used for a span of 10', to support a lattice roof, I have to question if that large of a beam is really necessary. So in a effort to "find out what is required" by the U.B.C. I thought I would post the question here. If someone happened to have one handy and was willing to look it up it may have helped. I will still be making a trip the library to see if they have one there I can look at. If the poster and myself both came up with the same answer, I would bring it up to the building inspector to get his take on it also.

So in brief I am not concerned (at this time in planning) about the lateral strength of the carport. All the bracing issues will be dealt with when the time comes.

 

Check out the web site below. Hope it helps.

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

 

Wirepuller,
Thanks, that did help out some. However, that gives me the lumber size I need for the rafters, using different spacing on centers. What I need is something to help figure the lumber size for the span between columns (the load bearing beam, the rafters are going to be supported by).

I tried to call the building department this morning, but it is Friday and they are all gone today. Tried to search the library catalog on-line, but it wasn't working either, so will have to venture out there in person later.

Small towns can be fun, but sometimes it is hard to locate the needed information.

The good thing, I have gained some additional knowledge!!!

Thanks and I will keep looking....

 

If you are just attaching the posts to the slab, you will need some lateral support or bracing for the posts somewhere.

Good luck.

Dick

 

Ok, maybe I am not using all the correct words here.

I am putting up a "free standing" carport, which is on the 10 x 20 slab. The "posts" are mounted in Simpson galv. post anchors, with the needed footing poured. I am going to use 4 x 4 posts, with three along the length of the slab on 10' centers.
I am planning on putting a roof on it which consists of nothing more than a shade cloth (at the most lattice). I was planning on using 2 x 6 rafters on 24" centers (may move that to 16").
Each post will have some sort of Post to Beam brace, for lateral strength. This may consist of a bolted on metal "L", "T" or Saddle bracket, with a diagnal brace. The diaginal brace will be notched into the beam and post (1") and bolted in place, or be bolted in place and have a 2" kicker on it. If this still doesn't give me a warm and fuzzy feeling as to the safety of the carport and lateral strength, I will run 1 1/2" strips of galv. strapping from corner to corner on top of the beams to further reduce the shear.

My only question is what size beam do I need to use to support a lattice roof, with 2 X 6 rafters on 16" centers, with a span of 10' between support posts?

Is that better, or still clear as mud?

 

I was just worried about the over-all lateral strength. It sounds like you are aware of the need for it.

All too often people forget about bracing because it is for a load that is not obvious and you cannot see. The more the deck/roof dead load is, the more bracing you need. In your seismic area it is really important. In other areas, wind is usually more important.

I spent time doing building failure analysis both during and after the Northridge earthquake after shocks. I saw many structures laying on the ground with no real sesmic damage to either the columns or beams. The failure was in the connections that were not able to handle the horizontal shaking. - I quickly learned about what I should have done when I was designing. The loads you see are the easy part - the stability is the hard part.

Again, good luck!

Dick

 

Appreciate your concern and I understand where you are coming from. I have seen the same things out here from time to time. We have to deal with some wind dangers also, so have tried to ensure this thing will not turn into a umbrella during a wind storm also, one of the reasons for going with lattice or shade cloth.