Needing some advice building a lean-to.

[RobJ]

I'm reading this - and is the sugggestion here that 2 - 2x10's can carry a 14' span of roof?
What about snow?

The Texas Gulf coast doesn't get that much snow. In the weekend place I built I have 2x8's spanning 14 and 12 feet with a 2 story above, no bounce...they are on 16" centers. There is a little overlap in the center that may help some. They are also SYP which makes a big difference.

Rob

 

[Chuck K.]

Eddie

What kind of straps should he (we) use? Do you have a pic you can post?

Also, I'm sure that you mean that the 4x6 post should be notched, but could you clarify? I am doing a similar build and it will be my first pole-built.

PS .... sorry to barge into your thread with these questions, Chuck, but I hope that the answers will benefit us both.

Thanks!

No problem what so ever CJ.. And thanks everyone for all the great information.

I believe I will attempt to find a 2x10 or 2x12' 24' long that will span the 14' opening and the 10' enclosed area, this way I will not have a "seam", one board seems stronger to me than a 14' butted up against a 10'. The 24' header board will be through bolted to the 4x6's with 1/2 or 9/16 all thread and washers

I doubt I will double the header because I plan on using joist hangers: Joist Hangers using this method I will not have the joist sitting on top of the headers .. OR I will go on 6' centers butt nail joists to the headers and cross nail into the 4x6's.. Yes Eddie I am heeding your advice about nails not made to support a load, if I go the later route I will use a through bolted jack stud to help support the load on the joists. Its very slow at work tonight so I may attempt another "high tech redneck CAD drawing" like the others

I realize placing them on top makes it stronger but using the KISS theory that I have to apply to myself (Keep It Simple Stupid) I can nail the joist hanger at equal distances to the headers while on the ground. Once the headers are up then I can cut to fit the joists and drop them into place. Beings this is going to be a one person job (with little expierence) this appears to be the best/easiest method.


I will then nail perpendicular (perlins?) 2x4s on 2' centers across the joist that I will screw my metal sheeting to..

I think I have a resonable game plan that I can do by myself but anyone wishing to come down is more then welcome beer and BBQ would be served

The most challenge part of the job in my opinion is getting my 4x6 posts in straight and square.. I have to do additional homework on a sting line batter box?

Thanks again all..
Chuck.

 

[EddieWalker]

I doubt I will double the header because I plan on using joist hangers: Joist Hangers using this method I will not have the joist sitting on top of the headers .. OR I will go on 6' centers butt nail joists to the headers and cross nail into the 4x6's..

I'm getting confused. A header is a beam that is strong enough to support the load of the entire house above it. A joist is just strong enough to support it's share of the floor and what's stored on that floor. The size of the joists is dependent on the span and the spacing of the joists. A header is sized on the distance it spans with the expectation that it will hold the maiximum weight of the roof and walls above it.

I might be wrong on this, but I've never seen a joist hanger used to replace a header. I do not think this is a good way to do this. I also don't think it's very dificult to cut the post and attach the header to the top of the post. This way, the post will support the weight of the header.

I'm also confused on what size lumber that you plan to use for the header? Are you downsizing it to just a single piece of lumber? A 2x6 is just $3. There is no reason not to double up your headers. They are cheap, easy to make and used in tens of millions of homes.

Eddie

 

[cjcocn]

Eddie

It sounds like Chuck essentially plans to build a floor and use it as his roof? I say this because his "rafters" will become joists (at least the way that he is describing the proposed construction).

Chuck

(Eddie, correct me if I am wrong here, please!!)

The header is that span that you have running 14' across the opening. There may be 24' long 2x10s or 2x12s around, but I have never seen one and if they do exist I imagine that they'd cost a pretty penny. As Eddie said, the header's purpose is to support the weight of the structure above it. The header can only do that adequately if the structure above it is attached securely enough.

Using joist hangers may not do that since the "rafters" will only be held to the header by a few nails (okay, maybe 10 per rafter). However, resting the rafters on top of the header will greatly reduce the chance of failure and will (my layman mind believes) better transfer the weight of the roof to the header.

As for the single piece header, I would advise that you reconsider this as well because a doubled header will provide greater strength (vertically - as in it will not sag as easily) and will also provide greater lateral strength (it will not twist as easily).

If you are concerned about the butt joint being too weak, then you could always use a 14'er and a 10'er to create one header. For the exterior portion of the header (the one that will show from the outside), you could lay it out so that the butt joint falls directly on top of the 4x6 post (right next to your tanks in the pic).

For the interior portion (that side of the header that you will only be able to see from inside your lean-to), reverse the order of your next 14'er and 10'er so that the butt joint is over the 14' opening. If you want to strengthen it, you could always run a fairly short piece inside the lean-to that equally covers the joint. You would essentially be adding a third layer of header that will help strengthen the joint. If you used a 10' "third" piece, just put 5' on each side of the joint.

If you are set on using joist hangers to make the rafter installation easier, then use 16' rafter material, nail your joist hangers to two separate pieces of lumber of the same thickness and width (if you are using 2x6 rafters, use 2x6 "end plates"). That way your only challenge will be to get the two end rafters up and nail up the end plates. Being slightly over 16' long (16' plus the width of the 2 end plates), you will have a bit of overhang on each side of your 12' wide lean-to. This will mean that the rafters are still sitting on top of the header (where they belong) and you can still use joist hangers to make roof construction easier.

Sorry for the long post, but I'd hate to have you build something that may fail.

If this is all as clear as mud, then I'm sure that Eddie can clear things up for us or offer up some better advice.

 

[Chuck K.]

I apoligize for using wrong terms between joists, headers, trusses, girts, perlins, etc. I screw them up regularly The reason I thought a single 2x12 24 foot long would be adequate is the open span is only 14' and the weight the 14' span would be supporting is the rafters and the roofing material which is standard gauge metal sheeting used on metal shops.. I am not sure what gauge it is.

Eddie sorry for the confusion wished I could describe what I have in mind better. If I doubled the header and set the rafter on top I do not know how to cover this area. I am trying to secure the rafters with joist hangers inside the frame work instead of on top... clear as mud?

I really appreciate you guys having patience with me.. My carpentry skills are second only to my brain surgery skills

If you understand what I am proposing and still think its a poor idea, I will double the 14' span of the "header" and place the "rafters" on top..

Here is a crude drawing of the overhead veiw of the framing of the roof.. Click on the "X" on the lower R/H corner to enlarge picture..

 

[cjcocn]

Chuck

No need to apologize! I am not an experienced builder myself and I can imagine that pros like Eddie have "fun" reading my long-winded posts that contain inaccurate terms. I believe that Eddie's attention to details such as terminology is due to his wanting to give the best advise/suggestions possible and he can do that a lot better if he is clear on which portion of the build that you are discussing. Heck, as far as that goes, I should be apologizing for my looong post that I put up last night!

Eddie is certainly the one that I'd listen to over my suggestions, but I still think that putting the rafters on top of the header is the best way to go. I would also consider using 2' centers for your rafters as opposed to the 6' centers that your drawing shows.

I am not sure what you mean when you say that "If I doubled the header and set the rafter on top I do not know how to cover this area."

If by "cover" you mean you are not sure how to put it together (construct it), then my response would be that it would be even easier if you did it this way. Use at least 14' rafters and you will have a 1' overhang on each side of your 12' lean-to (I would use 16' rafters and give myself a 2' overhang on each side). This would give your implements more protection from the elements as rain would be less likely to get at them. It would also make it easier to construct as your rafters would rest on top of the header and you wouldn't have to worry about holding them up while you were toe-nailing them into the header - they would simply rest on top of the header.

If "cover" means leaving less holes for the rain to get into, then the only extra thing that you would have to do is cut some short pieces of 2x6 (assuming 2x6 rafters) and put them in between the rafters to cover the gap in between them.

HTH

 

[MarkV]

Chuck you really need to use two 2x10’s for the header. One is not going to be strong enough on that long of span. If you join the 2x10’s together and set them in a notch on top of the posts you could hang your rafters with hangers if you want. I think it is extra work and expense though and you loose the ability to let the rafter run past the beam so you have an over hang. As far as closing or covering the space between the rafters you cut “blocking”, pieces of the same size material placed between the rafters to fill the gap. I still think for this application that you can run you rafters on six foot centers to line up with your rear posts. Many full size pole barns are built with trusses on 8’ centers. This is a light weight roof with no snow loads to speak of. If you were going to deck the roof and use asphalt shingles then you would need closer spacing for the rafters.

MarkV

 

[EddieWalker]

Chuck,

No worries about terminology, I get them confused all the time also. I still don't have a clear picture of what you are trying build, and maybe I need to start from the beginning. Are you building a lean-to that is attached to an existing building? Or is this a stand alone building?

Eddie

 

[MarkV]

Are you building a lean-to that is attached to an existing building? Or is this a stand alone building?

Eddie

Free standing with a shed roof Eddie.

MarkV

 

[EddieWalker]

OK, for a free standing building with poles, the big question is the roof design.

You will have to use a truss of some sort to span the distance from wall to wall. It's only 12ft from each wall, so this is pretty simple. First question is how much of an overhang do you want? None? a foot?

This is the starting point for the roof trusses. Decide on that, then you will know how long to buy the 2x4's that will make up the bottom part of the truss.

Next is to figure out what pitch you want the roof to be. Is there an existing house or building close by that you want to copy the pitch? The steeper it is, the nicer it looks and the better it sheds water, but the harder it is to walk on. 4:12 is a good all around pitch. 5:12 is about the max you can walk on safely. Less of a pitch down to 1:12 will still shed water, but it will also hold leaves really bad if you have any trees close by. It's also not very attractive.

Decide on your pitch and figure two 2x6's for the top parts of the truss cut at the angle of your pitch. For a 12 foot span, you can finish off your truss with a single 2x4 that is centered on the bottom 2x4 and goes straight up to the 2x6's.

The trusses will rest on the headers at the tops of your poles. To keep is at simple as possible, you can simply bolt your boards to the tops of your posts. Two 3/8's bolts per post will do the job. With your posts on 6 foot centers, I'd use 2x8's on either side of the posts. For the ten foot span and 14 foot spans, I'd use 2x12's sandwiched together with half inch plywood between them. For this, you will have to cut off the top of the post and rest this header on top of the post. This is the maximum way to gain all the strength out of the header.

To attach the header to the tops fo the posts, I would first toe nail them in place so it doesn't fall off while working on it. You can also install temporary boards up the sides of the posts to cradle the header in position. To make it easy on yourself, you can build the header in place. That's how I do it when working alone. Just put one 2x12 in position. then tack in the plywood, and then attach the other 2x12.

When done, this will give you a level line around the top of your poles to attach your trusses.

Putting the trusses on 4 ft centers will allow you to use 2x4 purlins on the flat to attach your metal. This is what I like myself, but you can spread them out further if you want to. If you do,then you have to put the purlins on edge. The further out you go, the bigger your purlins have to be. Rule of thumb is that for 6 feet, 2x4's on edge and for 8 ft, 2x6's on edge. You can make fewer trusses, but getting those purlins secure is tougher.

I'll stop here for now. Hopefully some of the others will catch any mistakes I made or clear up areas that are confusing. LOL

Eddie