Never Install a New Roof Over an Old Roofing System

If you are considering installing a new roof and are debating whether you should have it installed

over an existing layer of roofing, it is time to reconsider. This type of roofing technique is common in many regions and some roofing contractors believe this is a perfectly valid option for homeowners. If your roofing contractor recommends a lay-over or go-over technique for your new roof installation, they are recommending that you hire them to install new shingles over your old roofing system, and you should consider looking for another roofing contractor.

Most roofing contractors in Denver believe that lay-over roof systems will decrease the roof's life expectancy by twenty to twenty five percent. This means that the money you may think you are saving by having a lay-over roof installed is made obsolete because you have actually reduced the amount of time between roof installations. Additionally when a new roof does need to be installed next, the roofer will have to remove two layers of roofing which will make that job more costly for you.

Chances are if you are considering replacing your old roof, the roof system you have most likely has some problem areas that are causing problems in your home. Even if you haven't noticed a leak or water stains, chances are if your roof is approaching 10 years of age, it has leaks or problem areas that need to be addressed. Without removing the old roof and locating these problem areas, it is impossible to properly care for the roofing system, and laying new roofing over it could cause rot.

Rotting wood can hide under old roofing shingles that may look fine upon a surface inspection. Rotting areas need to be identified and replaced before you can consider installing a new roof. If you install a new roof over your old roof and there is untreated rot the areas will remain and worsen year after year compromising the structure of your home. When rot affects the wood under roofing materials, the nails holding the shingles on the roof cannot secure them properly and there is a greater risk of blow off, or shingle loss.


Another problem with go-over roofing, is the weight that is added to the supporting rafters. The added weight of extra shingles on older homes is a serious issue. Older home's framing standards are much different than today's standards. Some older homes have two by six rafter systems which support much less than today's two by ten and two by twelve systems.

Arguably the biggest issue with over-lay roofing is the eaves, rakes and valleys. These areas of the roof need special attention when the roof is installed. Especially in colder climates where issues like ice dams, snow and constant freezes happen through out the winter months, having new aluminum drip edges around the entire roof is extremely important. Without tearing off the original roof, it is impossible to properly install the new water barriers.

If you need a new roof, the best choice is to have an all new roofing system installed by the best roofing company Denver has to offer. Make sure they are a qualified, licensed and insured roofing contractor. Even if other options seem cheaper in the short term, the long term investment of a tear-off and re-roof will save you money in the long term.