upright and rafter spacing

[Raptor Chicken]

Very nice. Thanks for the input. It makes a lot of sense. Last week I had never heard of a purlin. I am going to do everything 24oc. I’m doing a double top plate because I want an overhang of at least 1 foot maybe 2

Thats a good plan but the overhang has nothing to do with needing a double top plate.

If the studs for your walls layout with the rafters you don't need a double TP. The reason for a double TP is for the possibility of a rafter falling in between studs on your wall. Proper planning can prevent this.

We have about a foot overhang on our coop that I showed above.

 

[mqoh]

If you were nearby I’d bake you some cookies. Can’t tell you how much I appreciate your help

oh, and you want your roofing screws to have approx 3 full thread penetrations thru your purlin - because basicall they ifrst three threads constitue the point of the screw and have no effective grip strength.

Into purlin vs Thru purlin is the difference between your roof peeling in a summer storm and a cat 1 'cane. In theory, the roof is stronger than that, but the same excellent ventilation we provide for our birds also means a lot of air can get under the roof and push upwards. Those tiny screws have limits - as does the thickness of the roof itself. More purlins plus more screws = greater resistance to wind uplift forces.

Stormcrow, Do I need to add a fascia board and drip edge to the high side of a lean to roof. I'm not worried about the low side as I plan to leave it open like your picture.

Since there is no reason to build it like a people house, it only need be strong enough that you can carefully walk on it occasionally for maintenance, I use 2' on center, purlins spaced approx 24" oc - and I use 5/4 x 6 pt deck boards instead of 1x4 grade 2s for my purlins. Locally, they are cheaper, pressure treated (in case there should be a leak), wider (easier to hit with screws from the top), thicker (more thread grip), and much less likely to have a knot in them which renders it structurally useless.

Did I mention they are often cheaper?

Here are some pictures of one I threw together in a weekend. That's the goat shed. I did something similar with the bunny barn I just extended off the shed.

/edit Thickness of your rafter is based on Span. For my purposes, I'll take a 2x4 to almost 10' unsupported length (meaning a 2x4x12, to allow me 1' of overhang on each end (roughly). I weigh about 165# and of course we have no snow loads. 2x6 for anything of greater span. Whether that's sufficient safety margin for you or not?? I can't answer that. they do make span tables.

Do I need to finish the high end of a lean to roof with a fascia board and drip edge. I plan on leaving the bottom open like your picture above.

 

[U_Stormcrow]

Stormcrow, Do I need to add a fascia board and drip edge to the high side of a lean to roof. I'm not worried about the low side as I plan to leave it open like your picture.

Do I need to finish the high end of a lean to roof with a fascia board and drip edge. I plan on leaving the bottom open like your picture above.

yes, I would fascia and drip edge the high side as insurance against windblown rains and as small deterrent against direct intrusion during high wind events.

 

[Raptor Chicken]

I'll just add that unless your coop is anchored to the ground in some way hurricane ties are a waste of time.

This coming from someone who's coop is NOT anchored to the ground.

 

[3KillerBs]

I'll just add that unless your coop is anchored to the ground in some way hurricane ties are a waste of time.

This coming from someone who's coop is NOT anchored to the ground.

Mine is built post-and-beam style with the posts buried 2 feet down.

 

[3KillerBs]

Likewise, with 120 or 160# of concrete attached to each post. I won't say it's not going anywhere, but I will say it's not going anywhere easily.

 

[mqoh]

Yes on center but thanks for checking

But doesn’t the roof attach to the pelum which is attached to your rafters so spacing the rafters would have more to do with strength than fitting material or am I wrong?

 

[Captain13]

We did ours as a post and beam structure with posts 8 feet apart and 2x4 uprights to serve as "nailing strips" for the hardware cloth.

Build thread here: https://www.backyardchickens.com/threads/large-open-air-coop-in-central-nc.1443812/

I really like your build. You might consider (if you didn’t already), adding Simpson Strong Tie straps to the rafters. That’s a lot of sail area and I saw some barns/outbuildings with the shed roofs lifted off when the remnants of Hurricane Michael came through here a few years ago. The Strong Ties will reduce the chance of that happening.

That is some fine building work you guys did there.