Considerations for re roofing a deck area are deciding to tear off the existing roof or install an new roof over the existing layers of roofing. After inspections of the mod bit roof installed only a few years ago we noticed a number of areas that are open on this condo building. There were also soft spots observed when walking on it. It was decided that this roof should be torn off and start with a new base.
Probing the roof in multiple areas to check the structural integrity of the deck or roof sheathing is a good test to determine if tear off is necessary.
Check to see how many layers of old roofing are on the roof by cutting a hole in the roof prior to re-proofing. Roofing weight should be calculated and the structure examined to determine if too much weight is being added to the roof beams before re roofing.
Seam failures caused leaks since this is rather a low slope roof. Seam failures appear to be the result of expansion and contraction coupled with inadequate bond between sheets in the touchdown process. We have encountered these openings often and they can be the result of the mod bit rubber cooling down too much after it is heated and before it is pressed into the previous sheet.
Many attempts to patch with roofing cement have not solved the leaks
After removing two layers of roofing extensive damage was discovered to the roof sheathing and structure. Most notable is the damage occurring around the railing posts. Poor anchoring has allowed movement at the posts and pitch pockets opened up. The railing had to be removed and reconstructed with new base plates.
Beam repairs and new blocking was added to properly anchor the posts since they were only bolted to the 5/8″ plywood before.
New plywood and 5/8″ cement fiber roof board was added. the deck was primed and a CTEM base sheet installed. Essential to controlling the expansion and contraction of the roof membrane is the cement board base.
90 mil CTEM top sheet was installed with heat welded seams that will not leak with ponding water. The railings were installed top mounted to allow easier sealing of the penetrations.
The heat welded seams of this CTEM roofing are positively bonded together, as opposed to the Mod Bit torch down roofing that relies on the heated asphalt to create the bond. In our experience new Mod Bit roofs generally have seam failures after about 4 years. CTEM roofs when protected can last about 40 years.