Expert: Bruce E. Johnson - 7/30/2010

Question
Hello, I live in upstate NY and we currently have a 28x68 doublewide on a cement slab with tie downs and jacks. It is blocked in instead of skirting. I believe most of the weight is on the jacks under the home, not on these block walls( simply because they were put in place after the house was set up) We would like to pour a pad off the front of the house for a 45 x 8 porch and cover it with a roof. Use 4x4 or 4 x6 for posts. I have read numerous places not to attach the roof to the doublewide. Is this doable if we put footers below the new porch pad? Or not do footers so both the roof and the house move freely? I don't really want to do a free standing roof apart form the house. Last thing I want is my roof to leak where the 2 come together because of the shifting in the winter time with the freeze line in the ground or the 2 halves of the house to pull apart. We originally had hoped ot tie into th existing roof ( do a shed oof and essentailly just extend the roof) Any help would be great..I am getting so many different ideas from people and not sure which could be right.

Answer
Hi Tracy, If it is done correctly you really don't have to physically connect the roof of the addition to the roof of the mobile.   But you do have to glue down a flashing between the two roofs to make a waterproof condition. How this glue is done depends on the type of roofing your mobile has.  If it is a synthetic Hypolon or fabric roof then you will need a special adhesive and flashing that is compatible with the synthetic roof.  If you have a metal roof painted with silver mastic then you will need to use a fiber reinforced compatible mastic.  The real reason it is not recommended for a roof to mobile attachment is that the structure of a mobile home roof is very minimal in design.  Don't get me wrong they are fine for what they are designed for but they don't have enough strength to support much more dead weight. And as mentioned above, if you have a special roofing on the existing roof you need to be careful as to how you flash between the two structures.  As far as a shed roof goes.  It would be fairly simple if you flash it properly.. I am including a simple sketch which you should review with a local roofing contractor prior to implementing.. In the illustration I have attached I tried to explode the view of the tie in to show you what materials I would use for a typical metal mobile home roof. I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson