...roof pitch in Missouri if...? I am planning to build out from the back side of a mobile home 8 ft and the existing mobile home is 14 ft wide. This gives me a 22 ft width from front to back. What is the desired pitch I would need to put on a roof over this whole structure in Missouri? If possible, I would like to offset the peak so that it can be held up at the peak by posts that will be flush with the existing trailer outer wall. Is this type of roof possible for one, and how do i figure needed lumber and pitch?

I live in Missouri, own a construction and roofing company, and also Live in a mobile home. There are no rules as to the degrees of slope to the roof. I can't for the life of me understand why you would want to make the additions roof tie into the peak of your mobile home. I'm assuming that you own your mobile home and the land it's sitting on. Once you do a room addition like your suggesting, it can hardly be considered a MOBILE home. Do you realize what would be required before the mobile home could be relocated if the addition roof is extended to the peak of the mobile home roof.
I would suggest you look into the posibility of a flat roof with a minimum slope of 1/2 inch drop per each foot. And have it covered with EPDM by a quilified applicator or a Modified Bitumen Rubberiod roof. The EPDM is the more expensive of the two but will provide better resistence to the elements including large hail. I also suggest that you have the siding (if vinyl) removed where the room will be attached and reinstalled with the proper trim and corners. We just had a hail storm where as the siding was damaged and it can not be repaired properly because the room was nailed to the original siding not allowing for it's removal. I assume your mobile home is on concrete blocks and it is at least 2 foot or more from the ground to the bottom of your exterior doors. If you want a shingle roof to match the one on your mobile home and tie into the mobile home so as to be less noticeable, consider dropping the floor below the floor level of the mobile home so as to accomidate a roof pitch of at least 3 inches per foot as required by all shingle manufactures. Good luck on your project, and consider consulting a knowledgable contractor before starting the job. Don't take the advice from a handy man, that's how all the problems here started in the first place.

A 22 foot wide structure in which the peak of the roof is centered would require the roof rafters to be at least 12 foot long on both sides to acheive the minimum slope required for shingles. I came back to your question and reread. If your planning on building a pole barn type structure over the whole thing and if the roof is going to extend several inches beyond the exterior walls more rafter length will have to be figured in. You can buy a small book at Lowes that contains all of the info your asking about. It's a carpentry measurment guide.

Most singlewides have about a 3-12 or 4-12 pitch (depends on the manufacture and model). You should be able to look up this info online, or by contacting the manufacturer. They can even tell you what shingles you have on your home if you give them your serial number. (SN can be found on the dataplate, which is often on the back side of a cabinet door, in the kitchen, or on the steel frame. Ive seen them chalked, stamped, painted, or welded, on the frame, either at the tongue, or the rear cross member, usually)

I'd suggest that you take a couple of photos in to your local hardware/building supply store, and ask some questions. They can usually ballpark the materials required for a project like this. Look for a contractor's board too... most of these stores will have a bulletin board with local contractor's business cards... whom you can contact for estimates. (Some will even work with you, if you want to do the majority of the work yourself).

Don't forget to check to see if you need a permit, or inspection in your area to put on an addition.

And finally... once the addition is complete.. check with your insurance provider and the state, about having the home designated as 'permanent' as opposed to 'mobile'. It should lower your insurance, and possibly your property tax.

Good Luck

Remember not to put any structural weight on the mobile home. It looks great at first, but it will slowly sink.