How to reach a roof shingles estimate that’ll tell you what quantity of shingles you’ll require for a roofing job? There are two approaches you can take to assess the area of your roof, and then execute a series of steps that give you a roof shingles estimate.
Doing a Roof Shingles Estimate – How Many Shingles Will You Need?
Roof shingles are sold as bundles but you can also order them by ‘squares’. The shingle bundles are packaged in plastic or paper, and of a size that’s convenient for a person to carry. Heavier shingles will need more bundles per square. Three tab shingles usually take 3 bundles to cover a square.
For a roof shingles estimate you’ll have to figure out the area of the roof to be covered with shingles. You can do this by the measurement method, or the sheet-count method. For re-roofing projects, other methods are available.
Roof Shingles Estimate by Measurement
An exact way to know how many bundles of roof shingles you will require is to jump up on the roof and measure each plane. It’s easy with rectangular frames as you just need to measure the length and breadth and multiply them. If your roof is too steep to walk on, then your roof shingles estimate will need to be more indirect.
You must first measure the floor area, making allowance for any overhang. Then you can use formulas to make allowance for the pitch (slope) of your roof and multiply the area by a factor that will differ for flat, medium and steep slope roofs.
Roof Shingles Estimate by Sheet Count
A sheet count method is quicker and more convenient than measuring the roof. When your roof is sheathed by 4×8 feet structural panels, you can simply count the number of panels, each of which will be 32 square feet. For sheets that have been cut, you can make estimates based on what part of it has been removed.
If the shingles you plan to buy come at 3 bundles to the square, then each bundle will cover approximately one sheet (32 square feet). So you just order the same number of bundles as you counted sheets on your roof. It may sound crude, but is generally accurate enough for practical purposes.
Roof Shingles Estimate by Shingle Count
A way to easily estimate shingle requirement if the old ones haven’t yet been stripped off is to measure the length of eaves on each roof plane (or estimate it by counting the number of tabs along the edges and eaves, knowing that each tab is 1 foot in length).
Then count the number of rows of existing shingles from eaves to ridge. Since the exposed part of each course is 5 inches, multiplying the number of courses by 5 (and converting them into feet by dividing by 12) will give you the dimensions needed. Multiplying them will tell you the area to be roofed.
Will You Need Extra Shingles?
If the only measure you base your shingles orders on is the area of the roof, you will definitely be under-supplied. Some shingles will need to be cut or trimmed to fit rakes or at starter courses, or near the ridge. There will be some waste and breakage. Against chimneys or walls, some shingles will need to be cut. Some cut-offs will be big enough to use in other places, but the rest will need to be thrown away.
To compensate for this loss, you will need to get a few extra bundles of shingles. How many will depend on the size of your roof and the quality of workmanship. The type of shingle also has an impact as laminated shingles usually generate less waste than 3 tab shingles.
No matter which ones you use, it is difficult to accurately predict how many square feet of shingles will be needed. It’s safer to plan a little extra, and then return any unused bundles to the manufacturer. Typical wastage is 1%, but this can go up to 5% with complex roofs.
Some roof shingle estimates will not take into consideration the reality that some shingles will be damaged. Shingles can slip off the roof while being installed, and while some won’t break and can be reused, others will be lost. Nailing can be improper causing some damage as well. Sloppy crews can waste even more material. Usually one extra bundle is enough for most roofs, but you can never be sure.
Roof shingles estimates are a composite of intelligent guesswork and experienced assessment. While pricing estimates are an important part of a roofing project, the number of shingles to be used will directly impact this when more expensive roofing material is being used. Expert contractors will be quite accurate at giving you fair assessments of the number and type of shingles to use.