What to do about rotten layer underneath newer layer

My house has a roof that is about 10 years old (The house is 50 years old). We just had the house inspected, and found that there are two layers of wood underneath the shingles. The bottom layer is most probably the layer that was on the roof before the current roof was put on. From the attic, you can see sections of the older layer that are rotted. It looks like the people who installed the current roof just covered the rotted layer with a layer of plywood. And now, from the outside, you can see that the roof has sections that are sagging. We originally though that we would have to have the entire roof redone (take out both layers of wood and install a new layer). But one contractor said that they could fix the problem by just replacing plywood in sections that were bad. And that they would leave two layers where they did not find any problems in the wood. They would even out the difference in the surface of the roof by using multiple layers of shingle. I’ve included a picture of what our roof looks like from inside the attic.


He gave me two prices: one that would cover redoing everything, and one which would cover the cost of replacing shingles and included two replacement sheets of plywood. The second price would go up as they found additional sheets of plywood that would need to be replaced ($60 per additional sheet).

Another contractor just gave us a price of redoing everything. His price was about $800 less than the first guys price of redoing everything.

“It looks like the people who installed the current roof just covered the rotted layer with a layer of plywood.”

Many of the guys here on the forum say it’s ok to go right over the top of existing wood, maybe one of them did it, lol.

I can’t comment on the price as that will differ highly via locale. I can tell you that to do it right you’ll most likely need the entire roof ripped to the bare beams. At the very least you will have to rip the top layer of wood and see what needs repairing or replacing on the first.

I agree, tear off the whole thing and start from scratch. Doing it the other way will only continue the sag and not repair it. Also there will have to be some bracing to help the sag out.

Why would they prefer to do that, rather than redoing the whole job? They are getting extra money for the extra work. I just don’t want to have to do this all over again in 10 years… or have to take some money off of the value of the house when we go to sell it.

BW i have no clue. I wont go over any wood unless it is skip sheeting for shake. You need to tear all the wood off.

Tear it off.
I doubled the plywood on my neighbors 10 yrs. ago. I look at it everyday. 3 tabs are on it. It looks great.
What is going on in his attic? I haven’t a clue.

A plywood overlay is only OK if the old deck is not wet and rotted. IN some cases it is a great remedy

its usually because of the job market and the competitive bidding system,they try to do something less than what the proper way would be in order to get the job--rip it to the rafters and start over--now 800.oo less doesnt mean a thing,examine the job specifications to see who is giving you the proper job–I`d be nervous about anyone willing to do patchwork on that mess—"low cost jobs often lead to expensive solutions"you only want to do the job once!In the long term, The cheapest way is to do the best job !

its time for a home equity loan so you can start the whole process over!!!