Re-roof question

I am re-roofing my garage which is attached to the house. House is vinyl sided, do I run the new shingles up to the J-channel or do I need to do more? Thanks.

Just but up to the J-channel. Nothing more to do unless the section is more than a straight wall.

You need to do more, you need to make sure the wall is flashed and installed properly .

If you think this too much, have roofer quote the gararge roof.

If the wall is not properly “step” flashed it will leak!!

are you laying over the old…or tearing off? if laying over just butt it up. if tearing off you need to step flash it. if you are tearing off and need to ask this question… it will leak. :wink:

thank you marshall.


I also step flash walls on nailovers, you may have to remove j-channel and cut siding to allow for installation of stepflashings between each shingle. Don’t understand why other “roofers” wouldn’t also do this.

Roof at J channel is flashed, I was just wondering if it was best to get the new shingles under it somehow. Thanks.

Slide your new shingles under the j-channel if you can, otherwise butt to it.
You can install new flashing if you like but it involves taking off siding, most roofers don’t do this for a roof over because roof overs are cheap to begin with.

For a roof over you should use a 40 or 50 yr shingle also, they will bridge the voids better.

If you are charging to cut siding, wouldn’t it be better to just tear off? I personally have never heard of anyone doing it that way.

Marshall Exteriors hit the nail on the head :slight_smile:

If you are charging to cut siding, wouldn’t it be better to just tear off? I personally have never heard of anyone doing it that way.
I dont think so it only takes about 1 manhour to cut most walls, and I just like to install the shingles the way the manufacturer reccomends and warrants. I personally have never installed a wall without flashing.

I don’t think lay overs are warranted anyway are they?
Like was said already if its a recover ive already tried to talk them out of it and theres no cash for cutting siding and installing 30 year details on a 10 year roof.
Why not I&W the eaves and valleys to.

wow here we go again!!! nailovers ARE warranted and if flashed and vented properly the shingles will last as many years as a tear off. I have never installed a nailover that lasted only 10 years. Just flash the stinking wall and do it right instead of cutting corners to save a few dollars. if you want to rely on caulk to prevent leakage just butt in to the j-channel and caulk it, if you want to do it right install the flashing the way shingles are supposed to be installed.

IMO you should only do a roof over if the original roof is in relatively good condition.
This means that the flashings are good to begin with, the shingles are not curled and the roof is applied straight.

You can tell the customer “we can’t roof over this, it needs to be torn off”, if the above conditions are not met.
A roof over is not as bad as we make it sound if the original roof is applied correctly.
We run into problems by going over roofs that really need to be torn off.
You can’t just roof over a previously forked up roof, it won’t turn out too good, you don’t have much to work with.
If you try to fix it by cutting the crooked rows and reflashing walls you will have a lot of time into it, you should just tear it off.
The customer doesn’t want to pay for this kind of labor to do it right, and they don’t want to pay for the tear off.
Do you do it for free?

The OP wasn’t talknig about a roof that was all forked up. I agree that a nail over isn’t possible on all 1 layer roofs. They were asking about a flashing detail on a nail over. My policy is to install flashing on ALL walls it only takes a little extra time and work to do it right. To each thier own, it seems worth it to me to take a little more time to do it RIGHT and not take the easy way out. If you do not want to take the time to flash the wall just butt it and caulk it.

If re-roofing, butt up?

You mean butted to the J-Channel?

I’ve always lifted the J, cleared it out of any debris and then butted the shingles up to the sideway laying the J back on top of the new shingles.

This way, any rain that runs along the siding still gets carried by the J and anything on the roof runs on the roof. The J sits tight on the roof. If there’s no leak before this work, there shouldn’t be any leaks after the new work.

If there was a leak before, then it needs to be addressed before the new work is installed…first course removal and re-flash.

If tear-off, all new step flashings all the way up, but with Ice & Water Shield first, slipped up under the siding as far as possible (8" max).

I’ve seen caulking put under the J to resolve leaking issues which only leads to the J being sealed to roof then popping & buckling when it expands and contracts with the weather changes which in turn leads to openings in the siding and this lets water in.

Does every roof you do have vinyl siding?
What do you do when you run into old cedar, aluminum, asbestos, stone, brick, etc…

Does buckling of the J or shingles concern you if forcing shingles under the J? Most siders install the J to close to the roof. Rarley is there room for shingles to slide in.

Here let me help you, while the others are bickering,lol

Re-roofing- loose term. If you are tearing of the old shingles, you want to recheck and do any flashing needed. Loosen the J-channel Carefully, enough for you to get the flashing and shingles installed, then renail it. Simple -just takes little more time.

If planning to Roof over existing- First determine how the shingles look now, The new roofing will lay exactly the same. For example, Torn ,brittle, etc. Once you decide whether to Lay-over or Tear Off. Then Install (New) everything in the the same manner.

Have Fun