Finding area of a roof.

[ChrisMcC]

Back side is basic - 15' x 55' for A=825' or 8.25 "square"

Front has a gable I think its called.

Heres a crude drawing.

[JD]

Finding the accurate area of the roof would require measuring the rake of the gable instead of just the footprint. The slope on 12' will add 3-4 inches I believe. You could find the hypotenuse using the Pythagorean Theorem , but it hurts my head just to type (cut/paste) the words. Point is, you would need to measure the 12' rake and the 15' main roof rake on the actual roof.

If you are estimating the number of shingles you will need, I just multiply that 16' number of the valley by 2. 32 extra shingles per 16' valley whether weaved or cut. You also need to factor the starter shingles and ridge cap if you are cutting shingles for ridge cap. So if the roof measure 30' across the the ridge cap from side to side this number would change to 32' (or 32-8 if you need to add for slope) When using standard 3 tab shingles for ridge cap, I usually just add a couple of bundles for a roof. I think it is actually 35 LF per bundle.

There is always waste when installing shingles on a roof. Once I have determined the number of bundles I need using the above calculations, I add 5%.

Hope this helps,
JD

[ChrisMcC]

I got on the roof and measured end to end, and the back side it was 55 ft. From the bottom (where the shingles meet the gutters) to the ridge was 15'.

[JD]

Well, I guess this is a math question. Arghhh Well, time for me to shine (NOT!)

Using the numbers on your drawing, both sides would be 825sf. The illustrations shows the math.

I also used my shingle computations from my previous reply to come up with the number of shingles. I do not actually estimate shingles for an estimate this way though. What I do on a plain gable roof, without valleys, dormers etc. is, I add 3' to the width and 2' to the length. So, 57x33 = 1881. I would order 19 SQ. The valleys would be 2 shingles times 16 times 2 valleys, or 64 shingles. Counting 22 shingles per bundle, I would figure 3 bundles or 1 SQ. For your roof, I would estimate 20 SQ. So, the figures are not exactly the same, but I don't end up going back to a supplier for $14 worth of shingles either.




JD

[ChrisMcC]

So approx, how much am I looking at to shingle a 20 square roof using 3 tab shingles? (doing it myself)

( I have done roof work, just never had to figure out cost, or materials needed etc.)

[JD]

You actually have a 1650 SF roof that I would order 20 SQ (2000 sf) of shingles for. Price depends on what you can get materials for. It has been a while since I have installed a shingle roof and a roofer friend of mine told me prices have soared since the $4 a gal gas prices. Neither my friend or I are familiar with retail prices. Contractors can get pretty good breaks from supply houses. 'Jim from Canada' may be able to help here since he recently had a roof installed.

Anyways, if you take a roll of Ice & Water Shield or WeatherLock and cut it lengthways down the middle (3' wide), you can install 18" on all eave areas and have enough left for some vents. If you want to do the ridge caps also, you will need a second roll. I will figure one roll. I will figure two layers of 15# felt over the entire roof surface. They are put on with a 50% overlap to get 2 layers. This is a requirement from most shingle warranties. You can use 30# if you want, but the warranties still require two layers. You would double the price of roof felt. 15# = 4 SQ, 30# = 2 SQ

Also, roof-top delivery could be available for anywheres from free to $150. Believe me, it is so worth it. They show up and use a lift or conveyor. The free guys might want you to load the roof while they hand them off to you.

These are just approximate prices. I think they are close to what you would pay. After making the jpg below, I think you may need one more roll of felt to complete the job.

Again, this is just how I would prepare the order. No guarantee that you won't need a trip to the store. New vent caps and replacement sheathing is not included in my figures.



JD

[tritontr]

Chris if you want somthing better then a static vent for removing the heat&moisture take a look at the Aura Ventilator at www.roofvent.com