Is it better to remove old shingles when replacing a roof?
With questions like these more details are usually required before a solid answer can be provided. For the majority of homes removing shingles is the best option while for others they are perfectly ok to leave the old shingles on. For example if you are wanting to install a metal roof over the shingles this is fine, as long as the shingles are in decent shape and the roof can support the weight. Since most homeowners use asphalt and composite shingles, if you are replacing the new it is advised to remove the shingles along with the underlayment and damaged plywood (if any).
Shingles while individually may not weigh a significant amount, as a whole become very very heavy. Each additional layer you add to the home will only put on more stress to the rafters, framing and plywood. If there are any damages or problems under the old shingles they will only be amplified by the new amount of weight. Good-quality shingles can add 350 to 450 pounds for each "square" (100 sq ft of roof, installed). This excess weight could cause the entire roof to collapse in some cases. One other factor not many think about is your draining systems. The roof you currently have over your head was designed with the gutter and drainage lines. If you increase the overall depth of the roof it makes it slightly higher than the drains. When big storms come you will definitely notice the water spewing all over the place instead of going down into the gutters.
Asphalt shingles weigh a lot once you cover the entirety of the roof and adding a new layer of shingles can increase the load on the support rafters greatly. This extra weight can cause problems if there have been water leaks in the attic or rotted support joists which hold up the OSB board and shingles. In addition to weight, adding a new layer of shingles on top of a previous one will increase the depth of the roof. This increased depth can affect skylights, flashings, dormers, HVAC equipment and draining systems. If you are planning on installing a new roof over an old one it is important to take all these things into consideration before the work begins. Most of the customers we have helped would much rather have a new roof be the only thing between their attic and the elements compared to old shingles being sandwiched in the middle. Some states across the country have laws which state that a home can have no more than 1 layer of roofing, It is always a good idea to check with the state regulations to see if having more than 1 layer is even a possibility.
Another problem that can arise with installing new shingles over old roofing materials is the ability to fasten the nails to the deck and rafters. When you leave old shingles on the roof and install new ones the space between the nail and OSB decking becomes smaller. This means that the nail has to support much more material and goes in the decking much shallower, this makes the roof weaker overall and can be more susceptible to wind damages over time. Sections of partly secured shingles can blow off during wind storms and cause a lot of headache, this is why we don’t recommend installing a new roof over an old one. Our business has many experienced roof contractors and they almost always recommend tearing off the old roof to replace it with a new one.
For those installing metal roofing it is good to know some general information regarding installation and the benefits of a metal roof. Be sure to do more research on the benefits and disadvantages of metal roofs before you get a quote from the licensed roofer. In general metal roofing should ideally be installed on one layer of existing roofing such as shingles, tile or shake as long as the previous roof is in good condition and there are no leaks. If you want to install a metal roof we can help along the process and offer a roof inspection to determine if the shingles that are currently on the roof are in good enough shape (before installing a new metal roof on top of them). If there are any spots on the roof that seem to be weak or compromised they should be repaired before installing a new metal roof and be considered the highest priority. If all of the older shingles on the roof appear to be healthy and strong then it is most likely ok and the support trusses under the shingles are more than likely not damaged. Call our roofers in Fayetteville today for a free estimate and to start your roof replacement today.
Shingles while individually may not weigh a significant amount, as a whole become very very heavy. Each additional layer you add to the home will only put on more stress to the rafters, framing and plywood. If there are any damages or problems under the old shingles they will only be amplified by the new amount of weight. Good-quality shingles can add 350 to 450 pounds for each "square" (100 sq ft of roof, installed). This excess weight could cause the entire roof to collapse in some cases. One other factor not many think about is your draining systems. The roof you currently have over your head was designed with the gutter and drainage lines. If you increase the overall depth of the roof it makes it slightly higher than the drains. When big storms come you will definitely notice the water spewing all over the place instead of going down into the gutters.
Asphalt shingles weigh a lot once you cover the entirety of the roof and adding a new layer of shingles can increase the load on the support rafters greatly. This extra weight can cause problems if there have been water leaks in the attic or rotted support joists which hold up the OSB board and shingles. In addition to weight, adding a new layer of shingles on top of a previous one will increase the depth of the roof. This increased depth can affect skylights, flashings, dormers, HVAC equipment and draining systems. If you are planning on installing a new roof over an old one it is important to take all these things into consideration before the work begins. Most of the customers we have helped would much rather have a new roof be the only thing between their attic and the elements compared to old shingles being sandwiched in the middle. Some states across the country have laws which state that a home can have no more than 1 layer of roofing, It is always a good idea to check with the state regulations to see if having more than 1 layer is even a possibility.
Another problem that can arise with installing new shingles over old roofing materials is the ability to fasten the nails to the deck and rafters. When you leave old shingles on the roof and install new ones the space between the nail and OSB decking becomes smaller. This means that the nail has to support much more material and goes in the decking much shallower, this makes the roof weaker overall and can be more susceptible to wind damages over time. Sections of partly secured shingles can blow off during wind storms and cause a lot of headache, this is why we don’t recommend installing a new roof over an old one. Our business has many experienced roof contractors and they almost always recommend tearing off the old roof to replace it with a new one.
For those installing metal roofing it is good to know some general information regarding installation and the benefits of a metal roof. Be sure to do more research on the benefits and disadvantages of metal roofs before you get a quote from the licensed roofer. In general metal roofing should ideally be installed on one layer of existing roofing such as shingles, tile or shake as long as the previous roof is in good condition and there are no leaks. If you want to install a metal roof we can help along the process and offer a roof inspection to determine if the shingles that are currently on the roof are in good enough shape (before installing a new metal roof on top of them). If there are any spots on the roof that seem to be weak or compromised they should be repaired before installing a new metal roof and be considered the highest priority. If all of the older shingles on the roof appear to be healthy and strong then it is most likely ok and the support trusses under the shingles are more than likely not damaged. Call our roofers in Fayetteville today for a free estimate and to start your roof replacement today.