Trying to get a home ready and discovered almost all of the water lines had burst at some point. We had to tear out large portions of the belly fabric in order repair everything and taping them back together just wasn’t a viable option. The inspector was (to put it mildly) less than helpful and really couldn’t give me any advice. As always, desperation breeds creativity so we cut all the bad fabric away, pulled out the wet insulation, and then stuffed back in a new layer of R-11. The sides parts of the fabric near the I-beams were in good shape but the middle was pretty much gone under most of the home. Owen-Corning sells a pink, flexible foam, 4 X 8 sheet with vapor barriers on each side. Had considered using Tuff R Board but it’s not at all flexible whereas the O-C product is very flexible. We inserted the board between the cross pieces of the frame and the belly fabric. The board extends over the remaining good portions of the original belly fabric. 1 X 4s then get placed between the bottom of the boards and frame cross pieces to support the board and keep it from sagging too much. We used 3 1 X 4s per sheet. Then we used the 6" belly fabric tape to tape the edges of the board to the remaining fabric and also taped the seams where 2 adjacent sheets butted up against each other. The sewer pipes were not a problem as we had 2 sheets meet under where they hung down below the fabric. A couple of half circles in each sheet allowed us to make a tight seal around the sewer pipes and then the two sheets butted against each other.
This method was FAST and you noticed the “tightness” of the repair right away inside the homes. No more drafts coming up from under the home. The Owens-Corning board (1/2" thickness) has an R-3 value and it says the product emits no greenhouse gas emissions. We finished the job in no time at all once we got the hang of it and it looks really professional - a big concern when dealing with the OH inspection process as they crawl under the home looking for any tears in the fabric.
Hope this helps someone else in a similar situation.