1. Basic Square Footage
You will need a measurement of the basic square footage of the outline of your roof. Remember that this includes every part of the house that is covered by a roof. Include every ell. To do this, you have to measure the length and the width of each rectangle that makes up the base of your house. Figure the area of each rectangle by multiplying the length times the width. Then, add all these figures together.
The basic area is not good enough for the calculation of overall roof coverage area. You will also need to add on an extra measure for the overhang of the roof that goes beyond the edge of the house. If you do not include this figure in your reckoning, you will be short on materials when you go to do the roof. It is best to include this roof replacement cost in the beginning rather than pay more for it later.
The basic square footage and overhang are measurements of the roof if it were level. Assuming you are not replacing a flat roof, you will need to consider the slope or pitch of the roof in your calculations for roof replacement cost.
Pitch is described as the number of feet the roof rises for every 12 feet of distance. For example, a low pitch might be 3:12, a medium pitch might be 6:12, and a steep pitch might be higher than 9:12. These categories are important in determining the number of shingles needed.
A special number is used to convert the flat, level measurements into 3 dimensional figures using the pitch of the roof as a guide. This number is called an approximate average roofing multiplier. For a low pitched roof, it could be from 1.15 to 1.25. For a medium pitched roof, the multiplier might be between 1.25 and 1.4. A steep roof would have a multiplier of anywhere from 1.41 to 1.7.
The basic measurement of the roof is then multiplied by the approximate average roofing multiplier for the given roof, and you arrive at a new, more accurate figure. If you use the wrong multiplier or do not do the calculations correctly, you can throw off your roof replacement cost budget.
5. Special Features
The measurements of a roof can be altered by special features such as dormers, end-walls, valleys, and chimneys. These must all be accounted for and there is no one neat, simple formula for figuring them in.
If you want to get all your shingles at the same time to get a price break, it is important to figure correctly. If you want to make sure you get enough of the same kind of shingles, you need the proper number. Finally, if you do not want to overbuy, you need an accurate estimate of your roofing material needs. A home remodeling company can help you measure and calculate to reduce the roof replacement cost.