Purlin size?

[RoeDylanda]

Hi, all, I'm heading into the home stretch with the coop, but I have a question that the mighty Google has not helped me to solve. I'm putting Ondura corrugated plastic roofing on the coop, and while their website told me all kinds of useful things about purlin spacing and nails and panel storage, I need to know what size wood to use for the purlins! Here's the coop:

It's 4 x 6, but with the slope and the extra overhangs to keep the rain off me

the actual depth of the roof will be 6 feet 4 inches x 6 ft 4" wide. The coop itself is framed with 2 x 3s except for under the deck, which is 2 x 4s. Edited to add-- it's way off center on the deck right now because it's not attached yet, so we can carry it into place without extra help. It actually lines up right!

Purlins look skinnier than framing in the illustrations, but I can't tell how much smaller. Any thoughts? Thanks!

 

[ChickenCrazed]

We used a 2 x 4 rafter with a 2 x 2 purlin on our coop roof...It has worked very well!

 

[RoeDylanda]

Thanks, Laura! I'm going to pick them up later this afternoon. Your reply is *much* appreciated!

 

[patandchickens]

I'd be real tempted to use 2x4s (or at least 2x3s) in your situation... if the purlins only going to be supported on the side walls, that is a 6' span, which is awfully far.

Well *actually* what I would do in your situation would be to put in at least one (maybe two, if you live in a snowy area, I am sadly too lazy to go back a screen and see if your post gives a location

) extra pieces of framing first, basically "rafters". In fact, looking at your structure, two would actually be a LOT easier to put in than one, b/c you could attach them to the vertical members on either side of the door on the high long side, and hopefully that would line up with the 'studs' on the low long side. You could use 2x2 or 2x3 for this if you want; just make sure they're lined up so as to be flush with the purlins.

So now you will have installed one or two intermediate "rafters" to support the middles of the purlins. In that case, 2x2 purlins would be fine as long as you are accurate with the placement of your roofing screws; you can even in principle use nominal 1" boards although I must warn you that a) the screw points will protrude and b) it will not be as strong in high winds.

Just for the sake of completeness, purlins on "normal" sheds are generally 2x4s. It gives you more leeway for inaccurate screws, and is stronger *and* cheaper than 2x2s

Good luck, have fun,

Pat

 

[RoeDylanda]

Thanks, Pat, I had the same thought after feeling how heavy the roof panels are, plus we get a ton of snow here. I'm adding 2 more 2 x 3 rafters front to back and then the purlins will be supported at 4 points. I've reinforced the heck out of this thing so far, why stop now?