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Old 06-24-2009, 11:12 AM   #1
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torch down small roof section


Could someone please verify I've got my mod bit installation correct?

This is information I've gleaned by watching manufacturer videos, forum posts, etc...

it's a small section only 9' x 12' flat roof and I want to do this myself since the 4 quotes I've gotten have skirted around replacing rotten wood and fixing a raised area where the corner flat roof meets a pitched roof. I'm going to ensure all this is taken care of as time is not a factor for diy...providing it doesn't rain before I'm finished.

PO installed shingles on this flat roof, I'm going to take it all off down to the decking and replace all the rotten decking, eaves, and trim.

1. I'm going to lay 1/2" perlite base sheets


2. underlayment, fiberglass roll roofing. Overlap at the eaves 3"


Question, do I now fasten the base sheet and underlayment both with metal cap nails or do I nail the perlite board down then lay the roll roofing down and nail again?

Is there a formula (spacing, etc...) to the metal cap nails?


3. install drip edge on eaves


4. torch down the cap sheet.
Do overhang the drip edge 1/4" with the cap sheet?


5. flash with metal roll flashing where the flat roof meets the pitch roof and where the flat roof meets wall....? confused on how to properly flash this and at what point in the procedure to do it. Two sides have eaves, one side meets a pitched roof and the other side meets a wall (face of house)

thanks

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Old 06-24-2009, 12:54 PM   #2
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torch down small roof section


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Originally Posted by ernst View Post
Could someone please verify I've got my mod bit installation correct?

This is information I've gleaned by watching manufacturer videos, forum posts, etc...

it's a small section only 9' x 12' flat roof and I want to do this myself since the 4 quotes I've gotten have skirted around replacing rotten wood and fixing a raised area where the corner flat roof meets a pitched roof. I'm going to ensure all this is taken care of as time is not a factor for diy...providing it doesn't rain before I'm finished.

PO installed shingles on this flat roof, I'm going to take it all off down to the decking and replace all the rotten decking, eaves, and trim.

1. I'm going to lay 1/2" perlite base sheets

The perlite board would be called a recovery board or insulation boardm not a base sheet, just for proper terminology.


2. underlayment, fiberglass roll roofing. Overlap at the eaves 3"

Overlap enough so the flame does not have a chance to smolder the perlite board insulation.


Question, do I now fasten the base sheet and underlayment both with metal cap nails or do I nail the perlite board down then lay the roll roofing down and nail again?

Is there a formula (spacing, etc...) to the metal cap nails?

About every 3" on the overlap seam and diagonal at the 1/3rd and 2/3rd points of the sheet, going zig-zag, about every 12" forward with each nail. The nailing pattern actually required should be listed on the manufacturers website for installation instructions, depending on which brand of Modified Bitumen you are using.


3. install drip edge on eaves

If you use a drip edge, don't use thin aluminum that is sold for shingles. It will warp from the heat. Use 24 Guage Galvanized Steel and buy an asphalt primer and brush or roll it on the flat roof surface where the modified bitumen will be torch adhered to it.

Better yet, use the 4" line on the end of the roll and use that excess to overhang onto the fascia board and do not torch that last 4" and then secure it top the fascia boards with a 1/4" thick x 1" high aluminum compression termination bar which should have slotted oval holes to install gasketed wood-tec screws into every 6" to 12" On Center. A hack saw blade will score the aluminum and then you bend it at that scoring mark and it will snap off cleanly or you can hack saw or sawz-all all the way through for a cleaner finished edge.




4. torch down the cap sheet.
Do overhang the drip edge 1/4" with the cap sheet?

If you use the 24 GA Steel Drip Edge, the horizontal face exposed portion should be butted tight to the fascia board.


5. flash with metal roll flashing where the flat roof meets the pitch roof and where the flat roof meets wall....? confused on how to properly flash this and at what point in the procedure to do it. Two sides have eaves, one side meets a pitched roof and the other side meets a wall (face of house)

Continue on with the Modified Bitumen at least 2 feet up from the transition from the flat roof to the sloped roof, without using the perlite board, but definitely using the base sheet rolls.

thanks
I can not emphasize enough how you should maintain a fire alert and be safety conscious. This is really not a DIY project, but you will be trying to do it anyways, so do it safely.

Keep 1-2 class ABC Fire Extinguishers on the roof with you, along with a bucket of water and leave a garden hose with the nozel twisted to idle, so you can grab it quickly and squirt it if anything gets out of hand.

Do not torch over any moisture or morning dew, as it will steam and bubble the melted bitumen and degrade the adhesion and seam quality.

At the side edge overlap seams, after you heat the seams, either use a heavy roller or a consistant foot pressure to gently ooze out about a 1/4" to 1/2" bead of bitumen.

Fires happen to old wood and especially to the perlite board insulation, which will Not burst into flames, but smolder for several hours and finaly catch another flammable organic product on fire, so remain on the roof for 1-2 hours after the final torching work is done and check for "Hot Spots".

Be careful. The ramifications are extensive if done unsafely.

Ed

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Old 06-24-2009, 01:43 PM   #3
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torch down small roof section


Ed, thanks so much. Let me digest this and see if I have any follow up questions.
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Old 07-10-2009, 08:01 AM   #4
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torch down small roof section


with the layout of my roof in the pic, which would be the best way to roll the base roll and cap sheet roll?



or...

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Old 07-10-2009, 10:52 AM   #5
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torch down small roof section


Like diagram # 2.

But, on the gable edge, I run an additional sheet vertically, from eave to the sloped roof tie-in, so the it covers up all of the tail ends of the horizontal sheets after they are installed. This way, I use the white 4" salvedge edge line as a guide for the overhang and a neat continuous smooth overhang, secured with an aluminum termination bar, fastened with wood-tec screws every 6" to 12" On Center in the Oval slotted holes.

Other people use a metal Gravel Stop Drip Edge flashing and prime it and torch right to the sheet metal, but I don't like the different expansion and contraction rates of the two different types of materials and the future lack of a quality bond fused to it.

Ed
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Old 07-10-2009, 11:32 AM   #6
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torch down small roof section


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Originally Posted by Ed the Roofer View Post
Like diagram # 2.

But, on the gable edge, I run an additional sheet vertically, from eave to the sloped roof tie-in, so the it covers up all of the tail ends of the horizontal sheets after they are installed

Ed, thanks again for the reply.

lost me a little on this part....according to what you're saying I would actually roll the base and cap in the direction as shown in diagram # 1 (horz). correct?

then roll a finish sheet (vert) to cover up the tail ends where flat roof meets pitched roof (gable).

do I have this correct or did I misunderstand?
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Old 07-10-2009, 12:42 PM   #7
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torch down small roof section


No.

Run the sheets parallel to the gutter eave edge, from left to right, up to, but not past the end gable edge of the flat roof. Then, run a full sheet parallel to the end gable edge, with 4" overhanging, from the eave to the sloped roof.

For the wall, I would cut 1/4 sheets, about 4-6 feel long, so you wind up with 10" wide material by 4-6 foot long. Then lay a sheet of plywood on top of the field area roof already done and heat up the 10" sections to stick about 5" on the flat roof and 5" on the wall. This presumes you have to lower portion of the siding off of that wall and then continue with the 4-6 foot sections past the flat roof to sloped roof pitch change transition.

WARNING:

Any open flame is VERY dangerous to work with, especially near an exposed wall.

The top edge of the wall material should then be nailed in ever 3" to 4" across the top of the flashing membrane, then the siding gets re-installed to counter-flash the membrane adhered to the wall.

Keep a garden hose, a bucket of water and 1-2 ABC fire extinguishers handy and maintain a FIRE WATCH for a minimum of 1 hour after you are done using the torch, looking for smoldering smoke and underlying hidden heat remaining.

I don't like to see untrained people doing this type of roof, because even supposed trained roofers start fires all the time and you should take out an additional insurance policy for your work through your home owners poicy by adding a rider or umbrella coverage, but you are probably going to be doing this anyways, so at least have a guide to do it right.

Many roofers may disagree with some of the methods, like the 4" overhang, folding onto the exposed gable fascia and then secured with a termination bar and screws, but for your situation, it leaves less chances for any seams to come loose from a sheet metal flashing, but the exposed 4" overhang will be something you need to consider cosmetically, otherwise use the Primed Sheet Metal Flashing version.

Ed
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Old 07-10-2009, 01:18 PM   #8
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torch down small roof section


understood,
I've got all the fire precautions taken care of as much as possible.

thanks for your time and detailed information.
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Old 07-10-2009, 04:04 PM   #9
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torch down small roof section


You are welcome.

Remember the philosophy of the famous architect, Mies Vanderow (sp?)

"Less Is More"

Less heat when torching and rollong the material out. You do not have to make it liquid like tar in a kettle, just starting to melt. Also pass the torch wand over the seam that it is going to overlap so it is a bit more tacky too.

But, BE SAFE!!!

Ed

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