How to measure your home for roofing materials? That is a great question and here are a few easy solutions to getting your material list down. I will first say that if you have a low slope like 4:12 to a 6:12 roof pitch then you will have it easy from just the roof top by measuring the planes. This is providing you are not scared of heights of course. There are a couple of rule for the initial measuring process.
1. For a Gable Roof you should add at least 12% for waste. 1 square equals 100 square feet of material.
2. For a Hip Roof you should be depending on how cut up with hips and valleys at 15 to 17% waste ratios.
3. For Architectural or Laminated Shingles you will need accurate Lineal Footage measurements of the hips and ridge to determine how many bundles of enhanced ridge caps you will need to ridge cap your roof. For every 20 LF. Of ridge on hips or gable ridges you will need to know the total LF to know how many bundles you will need. These shingles run cost wise from $ 42.00 to $ 55.00 per bundle and that is not cheap.
4. For Standard Strip Shingles you should be know that you can cut up 33 LF out of each bundle for your hip and ridge caps.
5. If you have a gable roof and you want ridge over ridge vent such as Cobra 2 or 3 by GAF / ELK. Know that ridge vent comes in 4 foot sections so that you can decide how much you will need for the overall ridge of your roof.
6. Standard nailing patterns call for 4 nails to every shingle and there are 78 shingles per roofing square and that comes to 234 nails per square if done to manufacturers minimal requirements. So for a 50 LB. Box of hand nails you will get around 25 square or 75 bundles of hand nailed shingles on your roof.
7. You will need to measure your valleys to see how long they are for Ice and Water Shield to protect your installation from leak. They come in 1 and 2 square rolls. A single 1 square roll has 33 lineal feet per roll and it is twice as much for a 2 square roll.
8. Last but not least you'll need felt and depending on your preference you can use a couple of different types. There is 15 LB or # 15 that comes 4 squares roofing felt and for 30 LB or # 30 roofing felt it comes in 2 square rolls. You'll also need to purchase some plastic caps to nail down the felt. You can install around 30 squares of felt with a 20 lbs box of 1 "plastic caps.
9. You'll need to know how many plumbing vents are on the house and the size of each one. They range from 1 1/2 "to 4" in size.
I hope this helps you out because I have used the same methods for 20+ years to get a material list in order for roofing residential houses.