Additional layers of roofing raises the price. When the layers are removed, this calculates more waste. The removal of multiple layers is more labor intensive. There is also a higher cost for disposing of old shingles. Most townships will only allow two layers of shingles on a roof. Sometimes an older roof may even have three. An additional charge is always added for multiple layers. So if your roof has 2 layers and your neighbor's has 1, all other things being equal, your roof estimate might be higher since we have to remove more layers from your roof.
Some homeowners may opt to cut corners and install a second layer of shingles without removing the first layer. However, if you have a problem with your roof, adding another layer of shingles will not solve it. In order to replace damaged plywood, shingles must be removed. Many times rotting plywood is impossible to spot until shingles have been removed. Flashing systems on vulnerable areas or sidewalls cannot be installed correctly on a second layer of shingles. A reputable shingle manufacturer will not extend their warranties to overlaid shingles, as adding a second layer will drastically decrease the life of the roof.
Many roofs built before the 1950s have a material underneath called "cedar shake". Current building code does not allow shingles to be nailed to cedar shake. The cedar is not a good nailable surface and will cause shingle loss. Because of this, all cedar shakes must be removed and new wood underlayment must be installed. When getting pricing to replace a roof with this underlayment, the price for all new plywood is included. Removing cedar is a very labor intensive process and takes much longer than roofs that already have plywood.
While it is impossible to determine with absolute certainty if any plywood will need to be replaced, a roof that has far surpassed its life expectancy may show signs of rotting plywood. A reputable roofing company will inspect the roof and attic (if possible) before providing a proposal. If the plywood shows obvious signs of rot, the roofer will include plywood in the cost of the roofing job.
If two houses are both roughly 1,200 square feet but one has a steep roof and one has a more gradual slope, the roof with the steeper pitch will be more expensive. A roof with a steeper pitch needs more shingles, as it has a larger surface area. Calculations of roof estimates are done by the overall surface area of the roof. Although interior surface area may be the same, the steeper roof is actually larger.
Although it may seem obvious, it is important to take into consideration if any additional work will be done along with the roof. Very often when roofs are replaced, homeowners will opt to have additional work done, since it's a good opportunity to have everything done in one shot. Comparing a roof estimate with someone who also had gutters done will obviously show a difference.
All of these factors can contribute to differences in roof replacement cost. If you are wondering what it would cost to replace your roof, just give us a call! Our estimates are easy, low pressure and free to homeowners. We find it important to take as little or as much time as you need to feel comfortable with understanding the roof replacement process and products.