Wood shed roof advice wanted

[TheRambler]

Howdy folks, I have started building a wood shed. So far I have the floor framed out and was hoping to get some advice on posts and the roof.

the details:
I have a metric butt ton of PT 2x6s from a deck that I redecked a year or two ago. Ranging in size from 8ft to 20ft. I am using this wood as I can to save on costs, mainly for the flooring in the shed. I used new PT 2x6s for the joists. So far I have the basic foundation laid out, all constructed of 2x6s, doubled up on the sides with 2x6 joists at 16 OC.

The area is not level and is gently sloping, I leveled the floor/frame off with cinder blocks. There is about a 24in height difference across the 20ft span

Dimensions are 20ft x 8ft, and aiming to be 8ft tall or so.

My plan is to use either polycarbonate panels or the other panels, (I forget what they are called, they generally have the same appearance as the poly panels but are solid/not translucent) that are right by them in places like lowes and home depot.

Questions:

How many posts do I need to support a 20ft span of polycarbonate panels? at least I think span is the correct term. I understand about the rafters, and the nailers or whatever they are called in regards to the number and spacing of those.
- My idea is to put up 6 4x4 posts, 1 on each corner and two in the center(1 front and 1 rear).
Would 6 posts be sufficient?

I plan on using a 20ft 2x6 as a header on the front, and the same on the rear. Do I need to notch the 4x4s to set the header into them or can I simply attach the header to the face of the 4x4?

Rafter sizing. Can I use 2x4s for the rafters or should they be 2x6 also? I was thinking that since polycarbonate panels are so light that 2x4s would be sufficient.
-I live in NW CT and we get a decent snowfall, so I would need to have sufficient strength to support a snowfall.
Would 2x4 rafters at 24in on center with nailers 12in on center be sufficient?

Hope that all makes sense, and thank you very much for the help!

 

[Doc C]

Don't nail the rafters to the face of the 4x4's with snow and really ever. You want your weight transferring straight down to the ground. If the rafters are on the face the nails might pull out.

It's hard to notch a 4x4 to accept a 2x. Your not left with a whole lot of the 4x4 left. If your set on using 4x4 post then look at Simpson strong ties to attach your 2x to your 4x4. They make many different fasteners and some are adjustable for your situation. Or make your own.

I will read this again in a minute and try to digest the rest of what your asking.

 

[Doc C]

This is my covered deck. It's overkill for a wood shed but you get the idea of what I'm talking about above.

 

[Doc C]

You mention poly panels so I'm guessing you are not using any type of roof sheathing under them? I have never worked with polycarbonate so I'm not sure how strong they are. But consider the snow will add alot if weight to your structure.

Based on the materials you have I would do 4x4 post with minimum of 4 across the 20' span including the corners. I would put a doubled up 2x6 across the top of the 4x4 the length of the 20'. Secured as the pic above or similar.

If you have 2x6 left over I would use them for rafters at 16" OC. 2x4 could probably be used at 16" OC but 8' is pushing it in North Idaho snow load, you might be ok where you are.

In a perfect world I would sheath with OSB or plywood on top of your rafters and then roof it. But it sounds like you want to run your poly on top of your rafters which is why I suggested 16" OC because I don't know how much the plastic will hold. Maybe someone else has that answers? If your are going to essentially skip sheet on top of the rafters with 2x4 then poly on top you might be able to get out to 24"OC but in all reality it's only a couple extra 2xs to do 16" OC. And if your poly goes direct on top of your rafters then you will probably need blocking between rafters.

Hope this is fairly clear.

 

[WoodyIsGoody]

In this application of poly-type roofing, you will need to insure the roof doesn't try to go from rectangular to a parallelogram because the roofing panels are not designed to add shear strength. In other words, you will be depending upon the rigidity of your vertical timbers which will need to be properly cross braced to insure the roofing fasteners don't encounter shear forces.

 

[Poindexter]

I looked into this a couple years ago. If you dont sheathe your rafters with wood, you will need a bunch (whats your anticipated snow load?) Of cross pieces, purlins, between each rafter.

For my local corugated stuff, if i didnt sheathe, for anticipated 50 psf snow load i was going to have to put purlins at 16 " on center between rafters on 12" centers, so the open sky visible from the shed floor would all be in 12 x 16 " boxes.

There is probably better corugated available in the lower 48.

 

[Jeffm1]

Mine is 8' x 24'. Four 4x4 posts (actually 8- front and back. Makes three 8x8 bays. 2x6 from each 4x4 post and 2x4 purlins every 18". Double 2x6 along the ridge running lengthwise. Snows in the winter here and holds up just fine. Ondura roofing panels. Holds 9 cords easy. (At 6 ft high all bays full)

 

[WoodyIsGoody]

Mine is 8' x 24'. Four 4x4 posts (actually 8- front and back. Makes three 8x8 bays. 2x6 from each 4x4 post and 2x4 purlins every 18". Double 2x6 along the ridge running lengthwise. Snows in the winter here and holds up just fine. Ondura roofing panels. Holds 9 cords easy. (At 6 ft high all bays full)

Looks nice! That's what I was talking about - the good cross-bracing on the vertical members.

 

[TheRambler]

Thanks for all the advice everyone. Pretty much all finished except for putting up some lattice on the sides to please the wife's aesthetics , putting on purlins, and the roofing panels. I ended up going with metal roofing...believe it or not it was dramatically cheaper when compared to the polycarbonate panels.

For my purlins, I am either going to do 16in OC or 12in OC, still researching that a bit. Should I use PT purlins or no? I know PT wood can do a number on fasteners, not sure how the metal roofing fasteners hold up to PT wood. Havn't been able to find a lot of info on them. The package says they are corrosion resistant but that doesn't mean a whole lot.

The purlins shouldn't ever get wet really, maybe on the ends a little. Would there be any real benefit to using PT?

Lastly, would I be better off using 2x4 purlins or would it be preferred to use 1x4? Locally the 2x4 is about $2 cheaper than the 1x4.

 

[Doc C]

Thanks for all the advice everyone. Pretty much all finished except for putting up some lattice on the sides to please the wife's aesthetics , putting on purlins, and the roofing panels. I ended up going with metal roofing...believe it or not it was dramatically cheaper when compared to the polycarbonate panels.

For my purlins, I am either going to do 16in OC or 12in OC, still researching that a bit. Should I use PT purlins or no? I know PT wood can do a number on fasteners, not sure how the metal roofing fasteners hold up to PT wood. Havn't been able to find a lot of info on them. The package says they are corrosion resistant but that doesn't mean a whole lot.

The purlins shouldn't ever get wet really, maybe on the ends a little. Would there be any real benefit to using PT?

Lastly, would I be better off using 2x4 purlins or would it be preferred to use 1x4? Locally the 2x4 is about $2 cheaper than the 1x4.

I don't think I would use PT. You might get a little water leaking through several years down the road when your rubber on your roofing screws start to dry out buy if you have good air flow I can't see it causing a problem.

As far as 2x4 vs 1x4...my initially thought was the screws might Crack the 1x4 but the more I think about it seems that either size board would probably be fine. 2x4 will add a little extra strength.

 

[kennyp2339]

Im also using the same ondura roofing, I have been mounting the roofing on 1"x4" perlins at 18" on center, the perlins are mounted to 2x4"s which are sloped at 13 deg pitch (roof is only 6ft long) So far I'm impressed with the ondura product, it really stiffens up when nailed using the companies nailing guide, I'm also building for snow load as we do get 30" nor'easters with heavy wet snow every year up my way.

 

[Jeffm1]

Thanks for all the advice everyone. Pretty much all finished except for putting up some lattice on the sides to please the wife's aesthetics , putting on purlins, and the roofing panels. I ended up going with metal roofing...believe it or not it was dramatically cheaper when compared to the polycarbonate panels.

For my purlins, I am either going to do 16in OC or 12in OC, still researching that a bit. Should I use PT purlins or no? I know PT wood can do a number on fasteners, not sure how the metal roofing fasteners hold up to PT wood. Havn't been able to find a lot of info on them. The package says they are corrosion resistant but that doesn't mean a whole lot.

The purlins shouldn't ever get wet really, maybe on the ends a little. Would there be any real benefit to using PT?

Lastly, would I be better off using 2x4 purlins or would it be preferred to use 1x4? Locally the 2x4 is about $2 cheaper than the 1x4.

I only used pressure-treated wood on the posts and end pieces that might be exposed to the weather but underneath the roofing panels is just untreated two by fours. I think that will be fine because it won't get exposed to the weather. So far it's been good...

 

[bob95065]

I used galvanized corrugated panels on my woodshed. No problems so far...