Do I need plywood?

Hello all, I know this question has been asked quite a bit but I could only find a bit of information pertaining to my question and I would like to get some more information from experts before making a decision.

I’m looking to replace a roof in the next few weeks and have obtained 4 estimations.

The last estimator recommended plywood to be installed in case of warranty issues, ie, the shingle company sending a person over to check the roof and not honouring warranty due to plywood not being installed when the new shingles were placed. Cost of adding plywood would set me back an extra $1500. He was still willing to replace the shingles without adding plywood though.

One other estimator mentioned wood as an option, and also said something about warranty but I could barely understand his heavy accent. Another estimator who did work on my nearby neighbour went up and looked around and said plywood would most likely not be needed but if anything came up they would let us know as they tore the old shingles off. They also installed a new roof for a nearby neighbour and did not add plywood.

Here is a little background information, the home is about high 30s years old and currently has interlocking shingles. It is located near Vancouver, Richmond to be exact and has a medium slope roof. According to the last estimator, there is currently shiplap decks on the roof.

Here are some info I dug up, … id=3962501 … roof-2.htm

Given I can’t access the attic, how would I go about checking the shiplap specifications mentioned in these articles?

Thank you for all your help!

Ship lap usually holds up really well. Do you have any leaks or noticeable damage? The sheating may just need refastened, and fix bad spots as needed. Sometimes this is something that can be very difficult to determine until the old roofing is removed.

I would recomend to sheet over ship lapped roof with new plywood @ 3/8. Or at the very least cover with 30lb felt.

Defently re-sheet and if you dont make sure they re-nail the shiplap and use #30 felt, but i still say re-sheet…

redeckin roofs is becomeing alot more popular. and it does make for alot better roof deck.
but if ya cant afford it. then hire the guy who dont need to do it.


Ship lap decks are better IMO than plywood. Its a ploy to get more money from you. as long as the plywood is good it will not effect your warranty. Now if the roof is installed wrong that does. I would throw the guy that said you need plywood re deck in the garbage. Ship lap rarely goes bad.

No reason to deck over GOOD shiplap

Most shiplap roofs around here are shot,you get the odd one thats not…

Thanks for the reply guys. So it really doesn’t make sense not to have an access to the attic (I just don’t ever visit the master bedroom)… and here we have some pictures of the deck. I took a measurement, they beams are 7 inches wide. Very few have gaps on them, and the ones that do are usually less than half an inch wide.

What does “shot” mean?(


So this should give a better idea. Last estimator came and didn’t even mention plywood =/.

No good,run out of life,replace or regret,had its life… :wink:

“shot” means it’s had nails pounded into it a couple times already and it now has splits,missing Knot holes, cracks and has shrunk up over time.It’s a pain to roof over, trying to find somewhere solid to put your nails and won’t have the same curb appeal as a fresh plywood deck.