help with roofing


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Old 03-29-07, 03:27 PM
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help with roofing

Ok today I bought Certain Teed GMS mop rolled roofing. I got the cold adhesive. I have been looking at how to install it and I thought that I just mop or brush the adhesive to the deck and roll it out but now I am seeing something else that I have to put a base sheet down first before I lay it down. Is this true or do I just put the rolled roofing directly to the plywood?
 
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Old 03-30-07, 08:44 AM
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You must place 15# or better yet 30# felt or tar paper first. Make sure you nail the felt down using a felt clip or washer on the edges of the felt. If you don't the rolled roofing will blow up on the edges.


After that, I would install the rolled roofing first without the adhesive. This is so that it will be straight and square. Nail at the top of the rolled roofing so that there will not be any exposed nails.

Once that is done, fold back the roll from the top down. Apply the adhesive aproximately three inches from the edge around the perimeter starting with the first layer of roofing (from the bottom edge). This application need only be 3-4 inches wide without speading with a stick assuming you have the liquid adhesive. Lay the first layer down and gently press it in the adhesive. Proceed to do the remaining layers.

I would recommend you overlapping each layer 18" to create a double layer of rolled roofing. Most people, however only lap it three inches for this is how it is made. Rolled roofing will only last 5 years under normal temperature. The hotter the climate the shorter life of the material.

Respond back with other questions.
 
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Old 03-30-07, 09:49 AM
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Ok sounds good but this all still applies to using Modified Bitumen rolled roofing? The vague instructions they gave was install a base sheet over the decking then lay the cold cement over the base sheet and spread it and then lay the sheets over the cement. I am confused cause I see all sorts of websites say different things. The base sheet they say is a special base sheet to adhere the two together.
 
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Old 03-30-07, 01:29 PM
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The modified roll is a different product than the 90# asphalt roll. The MB is installed with a 3-4" lap. The underlayment should be the fibered impregnated underlayment not the 15 or 30# felt. With the MB, since it is more ridgid, the adhesive can be applied as you go. Just make sure it is square and even.
 
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Old 03-30-07, 02:40 PM
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Thanks so much for your help on this. Just a few quick questions. Do I have to use any felt or vapor barrier under the base sheet or does the base sheet act like a barrier? Also is it ok to just use one base sheet and then the roofing over that? I saw one way done was the base sheet was nailed then another base sheet was glued and then finally the modified bitumen was applied over that. My last question is, the roof runs along the outside of the house (an addition) It is like a garage or a dormer if you can picture that. I am gonna have to remove that siding obviously up a few feet and I am not sure how it is flashed but it is working cause I have no water. My question is, do I install the flashing over the base sheets or do I install flashing and then install the base sheet over the flashing. Again thanks for all your help.
 
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Old 03-30-07, 04:35 PM
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Cover the entire area with one layer of underlayment. It is sufficient for the moisture barrier, just make sure it is attached securely with 'felt flanged nails'. The flashing will go underneath the siding and on top of the roofing. If the pitch is too flat then you can apply a bead of silicone sealent underneath the flashing in order to prevent water or melting ice backflowing under it. Be sure to install the roll all the way up under the flashing.

By the way, be sure to start the MB with a 1" overhang over the roof drip and gable edge.
 
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Old 03-31-07, 05:19 AM
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thanks so much for all your help. It is much appreciated!
 
 

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