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Stubits · Jul 15, 2009, 07:47 AM

I am in the planning phases on an addition and have some questions about the roof. It is approximately 5'x' in size and is a shed roof. It will abut an existing brick wall both on two sides, along the back and along one of the sides. The architect is calling for a 2/12 slope. I have a couple of questions as I will be doing the install myself.

1) I have checked and it seems as though there are asphalt shingles approved for a 2/12 slope. I understand this is a low slope, is there anything I can/should do to ensure a quality install that will last?

2) What type of flashing and method is used where the roof attaches to the house in the back?

3) I know that along the side where the roof abuts the house, step flashing is used. This is a two part system, correct? Step flashing is installed with the singles and then counter flashing is installed over the step flashing, right?

4) The side opposite the step flashing runs right along the property line and is above my neighbor's landing. I'd like to minimize the amount of water that drops from my roof down to his. Is there some form of drip edge or other flashing that can be installed, rather than allowing the shingles to just run over the edge?

Thanks!

dawgsnkats · Jul 15, 2009, 08:59 AM

2/12 is low slope. In order to keep water out, you should install an ice & water shield over the entire substrate before installing shingles.

It would be cheaper to install a mechanically attached membrane system than to install ice & water shield, then shingles.

A two part flashing is correct for both sides. At the peak wall where the roof meets the house, base and counterflashing is used. At the rake wall, you can use a combo of step and base or counter.

21boat · Jul 15, 2009, 11:15 AM

Hi stubits. An ice shield doesn't need to cover the whole sub straight. If doing that might as well use metal roof/standing seam and say done.
In the old days before rubber roof ( which I think you crazy not to use rubber) Sorry Guy. We used what is called "blind nailing roof cement" This is a cement that you coat the whole shingle ans stop the water from blowing under it. ( That's Probably why they invented mineral roll roofing) I use blind cement for low slopes in the look factor from the ground on very few occasions ( first floor) The rest of our low slopes is all rubber or standing seam

What type of flashing and method is used where the roof attach's to the house in the back?

When the second to last course of shingle is installed use flashing there like it's the last course and tuck under old roof 3" or so.

Cut that flashing wide enough to go over the second courses tab line. Now lay the last course that should just cover the metal and flashing lower edge. Roof caulk where the last shingle meets the metal between old and new roofs. Nial shingle down and don't' use blind nailing cement. If for some reason that roof bead caulk fails the water bypassing that will run under the shingle and on top of the flashing. Don't create a dam there. Use roof caulk to dapp top of exposed nails on last course. I thinking isn't that back wall a parapet wall. If so need to bend metal here. Lay first piece of flashing like i said but instead of going under old foof ben it up that brick wall 4" or so and let sit. Now take a grinder and grind out a horizontal mortar joint above that flashing you just laid. Take a new piece and ben a 3/8 or so and slip that in the 1/2" grounded joint. Use some short spiral masonry nails and nail into the grounded joint. The head of that nail needs to catch the flashing bent edge to 'Pin it in" To fill up grounded joint and flashing Butyl caulk is best and stays rubbery. Pure siclone is good also.

I said this a bit back wards. Temp lay out the flashing and counter flashing after the roof deck is on and account for shingle thickness. Grind out joint then and hose off/ pump spray off dust. This is down before shingle. Now the grind dust will no be on new roof.

Is there some form of drip edge or other flashing that can be installed, rather than allowing the shingles to just run over the edge?

Yes and you won't get it at the big box stores, roofing supply house. It looks like regular drip edge but it has an upright 90 at its edge mimicking a standing seam. Use it a lot in the city. This will stop all of the water on that edge

Stubits · Jul 15, 2009, 11:27 AM

I was planning to use a membrane, but the architect is calling for shingles now, given that it is a 2/12 slope. There are no longer parapets involved. Is EPDM still an option?

21boat · Jul 15, 2009, 08:23 PM

You bet. That marriage can be done. Also look down the road, I use rubber up to 3/12 if it can't be seen. Look at the lifetime use it provides..

We use rubber roof to go over old bad standing seams on warehouses Etc. Just buy a thicker fiberboard and cut to fit between the seams and rubber away.

The other caution I didn't mention here is a flat roof or a low slope roof receives Heat a lot longer then a pitch roof shadowing the other side of the roof at a certain time of day. HEAT is what kills shingles not rain ice sleet or snow. The heat dries it out. Less heat, longer shingle life.

Stubits · Jul 16, 2009, 02:45 AM

Hmmm. I understand how to install the roof when you have parapets on three sides and can just run the material up the wall and under the coping/cap, but what do I do here where that just isn't possible?

The roof itself will not be very visible, but I think the connection points will be. Specifically, I think you'll be able to see the back where the new roof joins the existing house AND the side where the new roof intersects with the old house as it slopes down. If I took the EPDM up and over the walls there would be a lot of visible material. I am afraid that will look pretty bad.

So, are there other ways of handling these points, other than taking the material up and over? Some sort of flashing?

Thanks!

21boat · Jul 16, 2009, 04:03 AM

Not exactly sure what your asking. What is the other roof out of.

If I took the EPDM up and over the walls there would be a lot of visible material. I am afraid that will look pretty bad

.
Its been a while sense I've see the pictures. I thought that roof was 3 stories in the back. Hard to see from the ground.

If your question is how to terminate the rubber without going up a parrot pit wall there are 2 ways to do this. One is use a termination bar that's made for this. Run rubber roof up the wall 6" And lay the bar over it. Tap con bar onto brick wall. SPM seal top of bar. That can be done on a slant/rake of roof or at the top if a wall is there. The other way is snap a chalk line on the rof rake where the brick is and use a 4" grinder to cut on the slanted chalk line. Run rubber up to line/grove tap con rubber into wall. Bend flashing slip in grove and masonry nails. Caulk brick grove. Or over kill. Termination bar and flashing over that. If you are going rubber to shingle. Lift shingle. Slip rubber under shingle. Nail through shingle caulk nail heads.

There is no step flashing using rubber.

Stubits · Jul 16, 2009, 04:19 AM

The issue is mostly with how it would look from the side and from that perspective, 3' for EPDM extending up and over the wall would be noticeable. You're right, it doesn't meet up with any other roofing material, just brick walls on 2 sides, gutter on 1 and nothing on the other. So glad to know I can use a termination bar.

So, can I ask an unrelated question? Ast winter I added insulation to my attic, really helped during the winter but nowthe house is much hotter than before. Any ideas why? Seems to be retaining heat. Now, I know the roof/attic is not vented at all. Could that be the cause? How do I go about venting a flat roof? Can I usw one of those solar powered fans? If so, how do I install it in my current roof(rolled asphalt or whatever it is) and be sure to avoid leaks. Is this difficult? If the fan is the way to go any suggestions on brands, sizes (roof is about 650 sq. Ft.), or any other tips?

Thanks!

21boat · Jul 17, 2009, 12:07 AM

3' for EPDM extending up and over the wall would be noticeable

Stubits. I remember earlier a conversation on running the rubber up the parrot pit and under the metal cap. That's one way. Its done but not that often. Simply run the rubber 6"up the brick wall and flash it or just use a termination bar. Ability no different then a shingle roof configuration except its rubber.

Now, I know the roof/attic is not vented at all. Could that be the cause?

... Yes

There is a myriad of venting for a flat roof. To install do it like the rubber boot you are going to put there for the plumbing. Install roof. Butyl or silicone caulk under metal flange, surface apply vent. I use Stainless Screws to install all roof boots etc. SS screws makes a cleaner look if the flange is visible.

For more flashing you can cut a piece of rubber glue it around a vent pipe/ or whatever An apron. That's the beauty of rubber.

Stubits · Jul 17, 2009, 03:10 AM

Excellent. I think a rubber roof is still perfect for the addition. Thanks!

Now, as for venting my existing roof, I am glad to know it can be done. Do you mind, yet again, a few more questions?

1) What are the different options available to vent a flat roof? The only one I have heard of is a fan, either powered or solar. Are there others?

2) If I use a fan to exhaust hot air from the attic, don't I need some way to replace that hot air? Otherwise I'd think it would just start pulling conditioned air from the house.

3) Is there anyway to safely install the fan in my existing rolled asphalt roof? I'll replace the roof eventually, but it is still working and there are other projects that need attention first, but the house is so hot and the a/c bill is killing me, so I'd like to do this sooner rather than later. So, how would I go about installing it in an existing roof? Do they make fans specific for flat roofs? Do I need to build a curb?

Thanks!

21boat · Jul 17, 2009, 10:07 PM

What are the different options available

Venting for these types of roof became real popular when Mobile became popular. Same pitches. Some have a sister natural fan that comes in sets 1st fan Sucks air out by natural heat and the sister fan blades re reversed to help push air in to replace air going out so a vacuum doesn't happen. Don't know what soffit set you are planning on the front short end and the small return

Otherwise I'd think it would just start pulling conditioned air from the house.

The fans for the dead air space in rafters. Add to that its Extremely Hard to pull A.C. up to any ceiling. One of the worst building practices of combined forced hot air and A.C. is they use a floor "Boot register" on the 3rd floor and not a 2 1/4"x12" wall stack with a Hi Low. The A.C. blows out from the bottom of the wall and sits heavy on the floor and then falls down the stairs. Misis Air return in hallways Etc.

Is there anyway to safely install the fan in my existing rolled asphalt roof?

Sure pretty much all roof surface vents come with recommended applications. Most now are just surface applied. Building the "Box" to raise it is for heavy snow areas. Ones that needed it before have been redesigned so none is needed

Stubits · Jul 18, 2009, 06:08 AM

As always, thanks so much for the great advice.

This seems very doable. I need to get this done ASAP because the house is miserably hot and I am going to go broke on AC costs. My electric bill is double what it was this time last year, before we installed the insulation.

So, do you suggest using a powered fan or just a natural one? Where do you normally buy these? I've looked at home depot and Lowe's and there aren't many options.

The design of the house doesn't really allow for any soffit vents at all. I was considering installing a gable vent on the front of the house. It is really the only option!

What I just don't know how to do is install the fan. Obviously I will cut a hole in the roof and mount the fan, but how do I seal it to the current roof and avoid leaks? Most of the instructions I've seen are for shingled roofs.

Also, how much ventilation do I need? How big of a fan? How much of a gable vent?

Thanks!

21boat · Jul 18, 2009, 08:21 PM

Hi stubits. You could start asking the company's that make trailers/ Modular double wide homes for roof vents. The other info call would be to your local HVAC supply house. Its been a Long time when I last got one. I believe it was a "Hart and Cooley" manufacture. Got them through My Plumbing supply house.

The general ratio for a pitched roof with soffit ventilation requirement when using a continuous system is a ratio of 1:300. A 1,500 square feet by 300 = 5 square feet for the ridge vent or gable vents.

Standard ridge vent produces 18 square inches of ventilating area per lineal foot.

Stubits to get to the minimum standard for venting a roof with no soffits is a lot to make up for, Basically it doubles the equation above. Anything there is better then nothing. The power venting is the way to go to move the air and pull in the intake roof vent.