Step Flashing only option?

I have just put an addition on my home and shingled the roof and was about to put flashing where the roof meets the existing wall:



I have loosened the board and batten siding and was about to slide the flashing (5" to run up the wall behind the siding and 5" to run over top of the shingles) and add a double bead of mastic under the section of flashing that covers the shingles.

A friend warned me that the only way to flash this situation is to use step flashing between each shingle along the vertical wall.

Is this true? All suggestions most welcome. As you can see, I'm now fighting the weather...

 

Step flashing is definitely the best, but it is installed as you shingle the roof. Flashing has to go under the shingles and up the wall, and by staggering them you gain water protection with each shingle. You may have a difficult time getting it under the shingles far enough, as I am sure you will have nails somewhere in there.

 

If it was mine I would have put the 5 inch flashing, as you were about to do, then also the step flashing. I would have cut the siding so there was a 3/4 inch gap between it and the shingles. Hopefully the shingles are new enough they can be loosened enough to get the flashing in place. Warmer weather would be nice too I am sure.

 

There's 6 inches of snow on the roof now, and I know the shingles are nailed up to within 2 inches of the vertical wall

Any ideas for a temporary solution that will carry me through until a major change in the weather/thaw allows me to pull up some shingles and add the step flashing???

 

Not really any thing to do temporary. Step flashing is the only way to complete it properly. If the inside isn't finished yet, it would be possible to remove the snow and heat up the inside of the addition. It may help in making them plyable. Just watch out the roof will be very slippery.

Here's a link to what it should look like. http://imgs.ebuild.com/cms/REPLACEME...50701082L1.jpg