I’m doing a slight repair on a house that I’ve recently purchased. I am attempting to repair a spot on the roof but I’ve seemed to have run into a problem of sorts. I had a couple low spots all running in a vertical line, so I tore that section of the roof of to replace the rotted wood, I found out that the roof had 3 layers of shingles on it. I need to make a temporary fix until I can afford to replace the whole thing. The roof doesn’t have plywood but instead has 3/4 in boards and the problem I’ve ran into is if I put 3/4 plywood down I would have to put 3 layers of shingles on to prevent a low spot where I did my repair. Can I instead stack 2 pieces of 1/2 in plywood on top of one another to build it up, or is the 3 layers of shingles the route I need to take?

You can use whatever is handy to fill the void and level it out.

I normally fill it back in with shingles, but I avoid this kind of stuff like the plague.

The best thing to do would be to replace the whole roof. If you don’t do that, then second best would be replace the whole side where the problems are. Lastly you could do the repair to just the smaller area but keep in mind, it will look like squat where it ties into the 3-layer part and if not done properly it can cause leaks as well.

You can use some loose shingles to “feather out” the drop off from 3-layers down to one. This will make the transition better but still won’t entirely eliminate the issue. Every nail head and place where two shingles fit together would need to be sealed up underneath the shingles at all unlevel spots being caused by the drop off. ( all spots that will throw water horizontally instead allowing it to continue down the roof vertically ) Basically the entire length from the gutter to the ridge where the one and 3 layer areas meet.

Best correct way is to bite the bullet and do the whole roof deck, as someone else said.

Best hack imo with that kind of height differential is to tar in a “Z” flashing at the transition.

Good luck.

id like to see some pictures.