The VHB tape is an extremely sticky double side tape used by body builders to fasten sheet siding to framing and itself. It comes in two thicknesses a thin on for sheet to sheet lap joints and a thicker one for sticking the sheets to the framing. Properly installed and you will destroy the sheet metal trying to peel it off. There are very detailed directions on how to prepare the metal and covering the installation, if not followed you will have joints coming apart. The tape also provided a barrier and thermal break between the aluminum and steel. There are several threads on this site that discuss the differences between using tape and or screws. Big thing to remember is the alum siding expands quite a bit and can and will produce some waves and wrinkles in the summer heat. the preformed metal studs and joists are quite strong, both the C shape and the Z shape are stronger than they appear, but only in one direction. they rely on the sheathing/siding products to give them lateral strength. I have designed many mobile office buildings for the modular industry with 11 ga. Z shaped joists and rafters. These support far more snow and internal loading requirements than a motor home will need. Aside from lower weight and cost, you get about 10% less voids in your insulation due to being able to insulate the framing cavities. It is still wise to use structural steel at the corners and framing around doors and large windows. the price of steel is very high and they charge a premium for the tubing. One would be very wise to listen to Blizz's advice on budget. you are combining RV with Big truck nothing for either of these is inexpensive. at my work we have to estimate materials for all types of buildings, and its still surprising what gets overlooked. If you can find something that meets your needs already built you will probably be money ahead, and far easier to finance. i have been looking for a good rig close enough to what I want that I could tear out the inside and remodel, but so far no luck. It does not help that I want a classic KW or Pete conventional with manual transmission. Most conversions are Volvo/Freightliner with the automatics. As far as the rubber roof, that is a easy project that you should not have any problem with doing your self. I have done two of my own RV's for a very reasonable price (less than $600 for my 30' class C.) First thing is to avoid any RV place for sourcing your materials. If you happen to have an ABC roofing dealer near you, they usually carry the Mule-Hide EPDM roofing (either .45 or .60 mil.), just order it about a foot or so longer and wider than your rig. They also have the water based glue to fasten it to the decking. Cover the whole roof, then cut out the openings for the vents and such, and fasten them down over the rubber. Eternabond micro seal tape then goes over all the joints and around vents. (This stuff sticks to anything in any weather forever..lol)
Dave
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