I need a carpenter's (pro or hobbyist) advice

[tpathoulas]

My sugar shack is located in my sugarbush, 3/4 mile from the farm or roads. I built a versatube metal carport and closed it in added windows and a cupola. Here's my issue. When cooking, the metal roof provides enough rain inside the shack to put out a california wild fire. I'm thinking off replacing the roof this winter before the sap run. I will use plywood, a water shield and then a metal roof.
My question, if I make rafters and attach to the metal roof rafters, is the spacing good enough or should I add more rafters in between the metal rafters. My building is 12x20 feet. and there are 5 metal rafters approximately 55 inches apart. too wide? rafter in between? Purlins?
Thanks in advance,
Tom

[Brian]

why not add hoods to the pans to control the steam instead of building a new roof.

[Pdiamond]

I agree with Brian.. Adding a hood to remove the steam will be much less expensive than re-doing the roof. With the span you have you would have to add rafters. Besides this time of year is not the best for completing a project like that. If you don't do things like this is there a local amish metal fabricator near you?

[tpathoulas]

Guys, good advice. I have given thought to a hood and will look into it. The problem will unfortunately still exist. As the cold metal warms, condensation begins and water starts to drip. The humidity accentuates the problem. Even today, I was in the shack and started my 2 burner sunflower heater and within minutes I had water dripping. The daytime is usually less severe, if sunny, the roof warms and water does not condense. But I tend to cook all night and you know the saying, when it rains it pours.
I'm thinking roof and hood might be best.
Thanks

[minehart gap]

Your plan to replace the roof will prevent the rain inside your sugar shack. The problem will move to between the plywood and the tin. The water shield will help but because the plywood on one side will regularly be a different temperature than the tin on the other side keeping your roof screws tight will be a nightmare and eventually your plywood will start to rot because roof screws will be missing and steam will saturate the underneath.
A different approach would be to install 2" closed cell foam insulation on the underside of the tin. That would lessen the temperature difference and therefore reduce the condensation. Plus it should last a longer time with less cost and less work. But make sure to have an air space between the insulation and the tin and also ventilate the inside cathedral ceiling peak.
I think that the advice stated earlier to look into a hood will help also but after you get the temperature/ventilation controlled.
And yes, that is too much distance for wood rafters to support purlins unless you would use 4x4 as your purlins.

[TapTapTap]

Unless you're a carpenter and a structural engineer, then you shouldn't modify a prefabricated metal building, especially the roof framing. Even the modifications you've made with the cupala may have compromised the structure.

From a structural perspective, the only correct and safe plan would be to rebuild the entire building frame - roof and walls from the ground up. At the very least, I would expect you'll need to add rafters but the extra roof weight will require more robust walls.

[johnallin]

I wholeheartedly agree with Ken.

That car port is only designed for a 22 lb/sq ft snow load! Adding anything to the roof will just increase the dead load - on the walls - and decrease the live/snow load capacity. You may be able to insulate with some lightweight foam board but adding anything like plywood or wood rafters is a recipe for collapse.

As it is, a 22 psf snow load is Not Suitable for any part of MN where 35 psf is the norm for the southern half and 42 is used in the northern half.

[tpathoulas]

Thank you all for the responses.
Weight has been a big concern as I have been thinking of doing this. When I enclosed the building I added 2x4's to the walls. They are not 16 on center but I could add more if needed to support a new roof.
My thoughts was to run a 2x10 down the length of the roof and then have 2x8 rafters running from the peak and sitting on the walls. I would join the 2x8's to the metal rafters but most of the weight would be supported by the wall. I was hoping by adding a little additional pitch I would reduce the load on the metal rafters. As I am a dreamer and not a carpenter or a structural engineer I was only hoping this would work.
I do like the idea of the closed cell insulation. How would I go about adding it securely? I am starting to look for someone who can fabricate a hood for me.
Thanks again. I really appreciate the input.

[bigschuss]

If you add enough 2x4's to support the rafters you should be fine. And if you make the roof steep enough (10/12 or 12/12) you will have almost no snow load.

[johnallin]

Thank you all for the responses.
Weight has been a big concern as I have been thinking of doing this. When I enclosed the building I added 2x4's to the walls. They are not 16 on center but I could add more if needed to support a new roof.
My thoughts was to run a 2x10 down the length of the roof and then have 2x8 rafters running from the peak and sitting on the walls. I would join the 2x8's to the metal rafters but most of the weight would be supported by the wall. I was hoping by adding a little additional pitch I would reduce the load on the metal rafters. ....

As long as you're not using any of the carport tubes to support rafters or a ridge beam, you should be fine. Lots of those kits are "engineering marvels" designed with minimal materials to make them affordable. Change or make one modification and it can be lights out. If that roof gets loaded to 35 psf, you've got over 8,000 lbs over your head.

[TapTapTap]

If you add enough 2x4's to support the rafters you should be fine. And if you make the roof steep enough (10/12 or 12/12) you will have almost no snow load.

Throw in a couple collar or rafter ties for good measure. Plus make sure your gable ends are structurally connected to the top plate supporting the rafters.

[afretired]

Not to take away from some of the good advise listed above, but if you want a cheap and fast temporary solution, you might try what I did. I too had a condensation problem in an area of my sugar shack. I took plant bed canvas, which is just real light/thin material, a bed sheet would work, and attached it to the bottom edge of my rafters. I don’t know if it partially insulates the roof metal, or allows the air to travel up the rafters keeping the moisture out. Anyway it doesn’t rain in there anymore.

[tpathoulas]

AFretired, That is a great, cheap and fast idea. Are you talking about the black fabric you lay down to prevent weeds?

[afretired]

No, it’s white and real thin, but anything like it would probably work. Cheap flat bed sheets would probably work. I just stretched it tight and stapled it to the rafters.

[afretired]

21726

This what I did.

[maple flats]

If you do add rafters, there is no reason to use 2x8's for a 12' wide structure. Does the top have a peak style or an arched type? If a peak, add a bottom plate then 2x4 studs max 24" spacing, thus 55" will need 2 between each, then a top plate. Add at least 1 or better 2 cross ties to prevent spreading. Then 2x4 rafters, or if concerned even 2x6 rafters. Then put plywood or OSB on it, then ice/water shield and finally steel roofing. As long as the rafters are 7' or less and you have a 3/12 or steeper pitch 2x4's are sufficient on a 3/12 or steeper roof (3" rise per foot horizontal). If you try the fabric idea I'd suggest just 1 season, then do it right.

[johnallin]

If the OP is going to be adding rafters, top and bottom plates, studs and then sheeting...may as well just build a new structure and be done with it.
I don't see how he can get any pitch at all unless the new "roof" is built over the top of the arch roof on the carport.
Adding to that carport is a bad idea...hanging up a sheet to absorb the condensation is harmless and will solve the immediate problem.

[Brian]

I still say hoods and run the vents through the roof, A couple Vent hat on the top simple done!!!

[Sugarmaker]

The thing about hoods and vent pipes, if designed correctly and installed correctly they should be able to remove 95% of the steam from the boiling room. We do have hoods and stacks and generally have only one or two drops of condensate per year off of a nail coming through the roof! Approximately 8000 gallons of water go out the stacks per year. or about 130 gallons per hour when boiling. I did bot want that in the room with me and friends, during boiling.
Regards,
Chris

[tpathoulas]

Thank you all for the replies. You've given me plenty to think about and i appreciate the help.

[therealtreehugger]

Something else to consider - and I don't know the answer to this - if you modify your sugar shack, and it collapses, will insurance cover it, or not, because you modified it. Something to think about.