do you really need new plywood over tongue and groove?

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Old 10-15-13, 01:19 PM
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do you really need new plywood over tongue and groove?

getting estimates. one was for a fortune to put new plywood over my existing t and g. they said they have to or the roof will be wavy. it doesnt look wavy and 2 other guys said they just would put over t and g

obviously if there is rot etc it needs fixed but as a general rule is it ok to just get rid of the shingles and put new over the t/g

PS the guy with the plywood wants 40K for the roof and 5 of that is extra labor because their truck wont go in my yard. i have one other firm estimate for 16K but im pretty sure thats no new plywood. both say 50 year GAF timberline

this is about 43 squares and the 40K guy told me 5K alone for shingles.
 
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Old 10-15-13, 01:21 PM
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If the sheathing is fine, it shouldn't need to be replaced. I would not be all that keen to add more over the top and I also don't know how that would remove waves.
 
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Old 10-15-13, 01:33 PM
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i dont know either but i emailed the 40K guy to remind me why he had to do the plywood again. if my 25 yr old roof looks 'ok' now, i cant imagine the new wouldnt be the same. they also sold a lotta extras along with this. X years of this warranty and Y of that. was more of a sales pitch than anything. 2 hours here. but did the entire thing in front of me.
 
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Old 10-15-13, 06:50 PM
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Keep getting more prices.
16K for 43 squares is about double what it would cost here in VA.
Adding plywood is not going to level out anything.
What's there truck going into the yard have to deal with anything?
Got some pictures of this roof?
Pitch, how many layers on there now, numbers of dormers, number of story's, valleys, ECT. all effect the price.
 
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Old 10-15-13, 09:13 PM
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If it's t&g I would say no. (more than likely you mean shiplap) But many houses are sheathed with a hodge-podge of 1x8's, 1x6's, 1x10's, all with spaces of up to 2" in between. Its the way they did it when a house was getting cedar shingles. If your roof sheathing is like that, then it's a definite yes.

If you go in the attic and look at the roof deck from below you should be able to see if it's solid (as shiplap would be) or if there are spaces (as most wood shingled roofs used to be).
 
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Old 10-16-13, 07:08 AM
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there's only one layer on this roof now. no pics of roof but perhaps i can get a google screenshot sometime. and there are no spaces between the t/g. it looks as pretty as a floor would. no gaps or holes.

i'm waiting for 2 or 3 other estimates but the 16K guy is using the exact same shingles as the 40K guy. so i wonder what more i could get for that 24K. oh wait, another 16K roof in 20 years if i do need it.

here's the 40K guys reasoning but i dont think i had a lot of this even on my 20 year old roof now so why would i later? and while i never measured my t/g i think its 6 or 8 inches so didnt know that woudl be considered narrow. also even as a layman i can see the t/g is in excellent shape and not a single nail rusted.

You are correct about us having to overlay plywood on top of the boards you currently have as decking material. As a company we do not re-install asphalt shingles over a board decking without a plywood overlay. There are several reasons why and here are a few of them. The boards are a very narrow width and usually random lengths, this creates far too many joints where nails will hit and not secure the shingles properly to the roof surface. Thus creating a spot for a potential blow off. With the install of a board decking material, especially the T&G boards, the home builders would run the boards in a way where the end joints donít always hit a rafter. This then creates a weakened area more prone to cupping, curling, splitting and even cracking over time. By putting a plywood overlay on top of the boards we can then ensure that we have a roof deck that is going to adequately support our roofing system properly and not cause issues later
 
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Old 10-16-13, 10:00 AM
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Don't you believe it. Your roof deck is far superior to any plywood or chipboard deck currently fashionable. His reasoning that your deck has too many joints & weaknesses is pure rubbish--the T&G's interlock to support the ends of adjacent boards. Unless the original install is shoddy or damaged there will be no gaps to cause a "miss" for the nails or staples used to secure the shingles.
 
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Old 02-10-14, 09:19 AM
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just wanted to close up the thread by saying 13K got me a great guy and he just finished the roof. i told him of the 42K roof and he was shocked. he said no issues at all nailing into my roof, just some rotten wood which is normal. recommendations from friends of friends really is the way to go. he owns the business and takes pride in the work and isnt some bigger company with faceless higher ups.

i didnt have the heart to tell him the 40K company charged me 5K extra becuase their bucket wouldnt reach the rear of my house. these guys did it all by hand and wheelbarrow. the profit on that 40K must have been astronomical
 
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