roof pitch

[beetlespin]

What is the least pitch I can use on a roof on a house in central NJ and how do I figure the pitch? The reason I ask is I'm putting an addition next to an existing room (old addition) and the present roof is rolled roofing.

[Rich]

I suppose you could put flat.. with flat roofs it's all in the details. Your parapet will need to flashed and capped.. all the corners will need some taper insulation to get water to flow to a drain.. drain will need to exit the building somewhere.. etc.
Grumpy could probably give more details on the actual construction details or point you in the right direction.

[beetlespin]

On a 1.25/12 pitched roof? :roll:

[beetlespin]

On a 1.25/12 pitched roof? :roll:

[grumpydasmurf]

"Rolled" roofign is a confusing term even to us roofers. Why? Because it can mean many different things. Is it a 90# minear roll or is it a roll of modified bitumen?

On a 1.25 pitch would definetly be modified bitumen. If you installed the 90# minear roll you'd be replacing your ceilings after a few good rains.

[Tom R]

If you're planning on going with 'rolled roofing' (mineral-roll), I believe the minimum pitch should be 2 in 12, for a 'shingled' roof 3 in 12.

To figure out your pitch for say, a 3 in 12 roof, the vertical difference in distance between he 'bottom plane' of your roof and the 'top plane' of your roof would be .25 X the 'width' of the side of your addition. If the side of the addition was say, 16', the roof would 'rise' 4' (3 in 12 = 4 in 16)

[grumpydasmurf]

Wow if you put mineral roll on a 2/12 please let me know so I can leave my card to do the repair. Honestly I wouldn't put mineral roll on a garage, maybe I would on a dog house.

[Tom R]

I wouldn't either, but it gets done around here all the time, and it's 'allowed'. (Central Jersey) By the way, I have a pre-existing 2 in 12 'rolled roof' on the back addition on my house. I've been here 10 years, - no leaks - , I coated it once with 'siverseal' when I moved in, and again about 4 years ago. I'm hoping to build an addition above it within a year, hopefully it holds out a little longer. Rolled roofing may be 'cosmetically gruesome', but it does serve it's purpose, if done 'correctly'. Personally, my 'rule of thumb' is 3 in 12 for 'rolled', and 4 in 12 for 'shingled', but then, that wasn't the question.

[grumpydasmurf]

Like I said I wouldn't put the rolled roofing on a garage, but it is done here also. I see it in the poor neighborhoods as a 3rd of 4th layer.

When I am installing a roof anything less than 3/12 gets modified. If it is 3/12 it's definetly getting 6' or more of ice shield... probably grace.

[beetlespin]

Does anyone know what the cost in Central NJ would be for a 280 sq. ft. modified bitumen roof? An estimate is fine. I am just trying to determine if this project is feasable. :D

[grumpydasmurf]

280 sq ft is small. Your looking at $1000.