Carport Build

[RobitussinPR]

Hi All,
Im building a carport lean-to attached to an existing garage. Haven't done anything this extensive before so learning a lot on the fly. Basic design is a 12x30ft carport, either 2/12 or 3/12 pitch with metal roof with 4 6x6 PT posts, and 3 10ft 6x12 beams on top of the posts. Planning to use 2x12 on 18 or on 24 for rafters. I am using some rough cut lumber for the rafters and beams (salvaged from a neighbor barn tear down,) wheras the posts are nominal, so it makes the joining a bit tricky. My main questions are:

1 - We set our footings and sonotubes (12in diam - 30in deep with about in above grade) for our posts, and got them square, but I think they are very slights out of level from one another. No more than 1-2inches. What is the best way to make sure the posts are trimmed to the the correct length? I suppose setting a new string line at the height of the highest post/bracket and measuring down and trimming as appropriate, but Id be curious about other ideas.

2 - Is metal hardware sufficient to join the beams and posts? I was thinking Simpson LPC Zmax 6x on either side of each post, since it appears I could slide the hardware out a bit to have it flush with the dimensional 6x12. The beams will **** onto each other over each post, and from my reading the 2.25in of support for each beam end should be sufficient, though I was considering a half lap joint to bolt the beams together. I was thinking to rest the beams directly on the posts rather than do any notching.

3 - Do I need knee braces to support the posts/beams? Ive seen them on some other similar builds but not on all. Id think the raftors coming off the ledger board to the beam should provide enough support to prevent racking, etc.

4 - Any reason to go with 1x4s on the rafters vs OSB before placing the metal roofing?

5 - I was thinking to throw some felt paper under the roofing to prevent drips, any reason to do this or not?

Thanks very much! I appreciate all the collective wisdom in this group.

 

[Hank11]

By your numbers:

1. If the tops of the concrete footings are obviously out of level I would cut them to match. If looks don’t matter, then either measure the differences and take it out of each post. Or mount the posts up and trim them in the air. You should buy or borrow a laser. What you have in front of you will get lots easier with a laser.

2. Metal can do the job, but I have no idea which you are referring to. I like your idea of half laps over the posts. I’d bolt through the beams with a T plate on each side. If you can buy rough sawn 6x6s will they come close to your repurposed beams? That would make a simpler and cleaner assembly.

3. Yes to knee braces.

4. OSB will be ugly as hell and likely start decomposing in a few years. A leak will make it worse.

5. No paper, just nailers. I’d go 2x4 to keep with the beefy look and no nails poking through.

You do know this is massively overbuilt? Unless you have six foot snows to deal with.

 

[RobitussinPR]

By your numbers:

1. If the tops of the concrete footings are obviously out of level I would cut them to match. If looks don’t matter, then either measure the differences and take it out of each post. Or mount the posts up and trim them in the air. You should buy or borrow a laser. What you have in front of you will get lots easier with a laser.

2. Metal can do the job, but I have no idea which you are referring to. I like your idea of half laps over the posts. I’d bolt through the beams with a T plate on each side. If you can buy rough sawn 6x6s will they come close to your repurposed beams? That would make a simpler and cleaner assembly.

3. Yes to knee braces.

4. OSB will be ugly as hell and likely start decomposing in a few years. A leak will make it worse.

5. No paper, just nailers. I’d go 2x4 to keep with the beefy look and no nails poking through.

You do know this is massively overbuilt? Unless you have six foot snows to deal with.

Appreciate the feedback. I live just east of the cascade crest, so we routinely get 4ft snow loads, and the carport will be north facing so it wont melt off all winter most likely. Even then its probably overbuilt but I got the lumber and dont really want to store it so figured I might as well use if for this.

 

[bb29510]

im doing the same thing but i poured (3) 10 inch, 12 ft concrete post with four feet in ground, then I going frame with 8 inch 20 ft metal cee and 20 ft purlin with metal roof the cee are attach to the concrete post with weld plates

my posts has 5#5 rebar with a #3 spiral holding it all together

 

[hefnerconstructionlc]

Your not over building. Those dimensions seem reasonable. Building a covered deck with similar beam, size, dimensions,piers,etc and my engineer plans had very similar sizes.

 

[RobitussinPR]

im doing the same thing but i poured (3) 10 inch, 12 ft concrete post with four feet in ground, then I going frame with 8 inch 20 ft metal cee and 20 ft purlin with metal roof the cee are attach to the concrete post with weld plates

my posts has 5#5 rebar with a #3 spiral holding it all together

that sounds pretty rad, and also well beyond my skillset! do you have any pics of the posts? I dont think I quite understand what you did. I used 4 #4 rebar for my footings and 4 more for the sonotubes.

 

[jonesg]

its easier to cut wood than concrete.

 

[bb29510]

.

 

[Monza Harry]

You could add a well anchored cap to the concrete instead of, probably easier overall than cutting the existing cement or custom cut lumber. Harry
Edit at that height a decorative cap with concealed shimming may be the answer your looking for, my thought is some decorative trim attached to some ply/lumber height adjusted of course.

 

[bb29510]

,

 

[bb29510]

so we was doing some auger cast piles on the job and we had nine cages left over, so that how i ended up with the rebar, 10 ft cages 5#5 with #3 spiral

 

[Firebrick43]

There is no reason to put a 6x12on top of the post. 2x12x20 nailer/screwed on both side will do better as to tie things across multiple post better and still be overkill for the rafter loads. Place the joint on top of a different post inside vs outside

Make sure you use hurricane strap up and over the rafter with proper nails/nail schedule to prevent uplift taking the roof that is a problem with open sided structures.

There is no reason to use either osb or 1x4’s with metal roofing.

Almost all pole buildings use 2x4’s purlins on face if the trusses are 4’ or under. Depending on the metal thickness/design they can 18”-24” OC.

 

[Zeke]

its easier to cut wood than concrete.

For sure. Stand the posts and use a water level. If that can't be accomplished then the carpentry skills aren't sufficient to do any more. It just gets more difficult as you go. Rafters require some knowledge.

 

[RobitussinPR]

There is no reason to put a 6x12on top of the post. 2x12x20 nailer/screwed on both side will do better as to tie things across multiple post better and still be overkill for the rafter loads. Place the joint on top of a different post inside vs outside

Make sure you use hurricane strap up and over the rafter with proper nails/nail schedule to prevent uplift taking the roof that is a problem with open sided structures.

There is no reason to use either osb or 1x4’s with metal roofing.

Almost all pole buildings use 2x4’s purlins on face if the trusses are 4’ or under. Depending on the metal thickness/design they can 18”-24” OC.

I was under the impression nailing 2x12 to the post face to hang the rafters on moves the load from the post/footer to the fasteners between the post and those 2x12s, which decreases the load bearing capacity significantly. If I were to go with a 2x12 I thought I'd want to notch the post to have the 2x12 face flush with 6x6.
I don't have another use for the 6x12 so even though it's overkill I figured I would use it here. Also, last winter was heavy out here and I saw numerous barns and carports collapse so Id rather overbuild than have to rebuild in 5 years.
Happy to be corrected in these thoughts and I appreciate the perspectives! I am a novice builder so learning a lot on the fly with this project...

 

[Firebrick43]

Fasteners are fine but notching would be the best. Just setting 10’ long beams on top would be sufficiently strong in the vertical loads but doesn’t tie the post together well or doesn’t take wind shear loads well unless you have expensive steel brackets that tie everything together well

 

[u2slow]

Here's my 14x40' lean-to...


10" sonotubes were enough, per code. Each has a 1/4" steel galvanized post saddle. The posts are 4x 2x6" and the beams are 4x 2x12".

 

[Hank11]

I was under the impression nailing 2x12 to the post face to hang the rafters on moves the load from the post/footer to the fasteners between the post and those 2x12s, which decreases the load bearing capacity significantly. If I were to go with a 2x12 I thought I'd want to notch the post to have the 2x12 face flush with 6x6.
I don't have another use for the 6x12 so even though it's overkill I figured I would use it here. Also, last winter was heavy out here and I saw numerous barns and carports collapse so Id rather overbuild than have to rebuild in 5 years.
Happy to be corrected in these thoughts and I appreciate the perspectives! I am a novice builder so learning a lot on the fly with this project...

I think you are correct.