» No Plywood Under My Shingles!

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  Post subject: No Plywood Under My Shingles!
PostPosted: Sun Sep 24, 2006 3:15 pm 
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This home was built in 1953. I purchased it in 1999. I am getting ready to have the existing three layers of shingles torn off and a fresh new roof put on :)

I am also having a central air system put in, and I ripped up a 5x5 ft pad where the unit will sit. When I got all three layers off, I was surprised to see that underneath there is not solid plywood but slatted like 1x4in planks! I can see right through into my attic :shock: And the planks don't seem very strong, like I could put my foot right through them. So...

What are the advantages/disadvantages of having this type of roof? Could I, should I have the roofers slap new plywood over the planks?

Hammer


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PostPosted: Sun Sep 24, 2006 3:33 pm 
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Having a wood plank roof deck is not a bad thing; however, without seeing it I can not tell you what to do. I will say that it won't hurt to have a layer of plywood installed over the planks, and may even be a good idea if there are large gaps between the boards. Just be aware that a thin plywood like 1/2-inch may look wavy on the roof, whereas a thicker plywood like 3/4-inch may produce ridges at the joints depending on the condition of the existing roof structure. Also, if you add plywood make sure the roofing contractor uses metal edge flashings that are of sufficient dimension to cover rakes and fascias to the same degree the original flashings covered the wood around perimeter of roof.

Now, forgetting everything I just told you, if the existing roof deck is tongue-and-groove or ship-lapped, you will probably be alright with what is there. However, if you are saying you can put your foot through the boards, I have to wonder if they are damaged or if you are talking about kicking your way through the planks?

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Last edited by Cerberus on Sun Sep 24, 2006 9:44 pm, edited 1 time in total.

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PostPosted: Sun Sep 24, 2006 3:56 pm 
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Thanks for the reply. I think 90% of the planks are in good shape. I know of a few spots that feel weak under the foot, which probably means a few cracked planks. Iit would take force to crack/punch through a good plank. The planks are not interlocked or overlapped, there is 1/4in space between them.

Overall the roof has a wavy look to it. It just doesn't look even. I would really like it to look more flat. Maybe plywood sheets could get it to look more even.

Hammer


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PostPosted: Sun Sep 24, 2006 8:42 pm 
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if your goin to put shingles back on.
put 1/2" plywood over 1x.


gweedo


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PostPosted: Sun Sep 24, 2006 9:47 pm 
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I'll meet you half-way gweedo.......put 5/8-inch plywood over the existing roof deck. The 1/2-inch would be fine, but the extra 1/8-inch will provide a better substrate for the nails, which will help prevent nail pops in the future.

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PostPosted: Mon Sep 25, 2006 12:21 am 
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Hi,

3/8" will do the job.
1/2" is what we normally use. You already have 1 1/4" of holding depth.
5/8" is a waste.
3/4" is reduculous.


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PostPosted: Mon Sep 25, 2006 12:56 am 
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That's true, I was thinking about how much penetration there would be if you hit the gaps between planks, and got side-tracked into thinking about the whole job that way. I wouldn't go with 3/8 personally, but the 1/2 should do the trick, then again I'm a consultant and more is almost always better to us. :mrgreen:

Now here is a question for all you shinglers. Would you use clips between the new plywood? I wouldn't think so, but then you may want to add it for expansion of the wood. Anyone here have experience with overlaying existing sloped wood roof decks with plywood with and without clips, and then seeing the finished product years later?

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PostPosted: Mon Sep 25, 2006 2:53 am 
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Hi,

Clips would serve no purpose. Except to make the job difficult. Clips are use to take the place of the missing rafter[loose explaination]. You are nailing the plywood down to a solid wood surface. How could it sag?

You use an 8D to gap the sheathing.

3/8" is plenty for this reroof. It is like putting luanan down for a sub-floor. You are just making the surace smooth. You are not looking for holding power or structural strenght.

I have been putting plywood down over planks and skipped sheathing for 25 years and all mine look good.


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PostPosted: Mon Sep 25, 2006 4:54 am 
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So you just use the shank of an 8d nail for your spacing? I was wondering if most roofers just butted the plywood together, installed clips for spacing, or used another method other than eyeballing it.

And for what it is worth, the H-clips are generally used to provide a gap and to provide rigidity between two sheets of plywood between rafters. From what I know about sloped roofs, I have generally noticed that H-clips are used on 24-inch on center rafters moreso than 16-inch on center rafters.

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PostPosted: Mon Sep 25, 2006 3:54 pm 
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put nails thru plywood, then thru 1x, then into rafter,

glad plywood clips were mentioned so i can take a minute to bash them.
cant stand the damn things and cant wait for the day there taken off the market. dont do nothin but poke holes in your roof.
if your worried about wood movin aroud then get thicker wood.
done torn off thousand roofs without plywood clips and aint nothin wrong with em, put the roof rite back on without em.
stupid ass plywood clips.

now i feel better.

gweedo


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PostPosted: Mon Sep 25, 2006 6:53 pm 
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Thanks for all the replies...

The central air installer are here NOW. I called my contractor, who asked the roofer if he should lay down plywood sheets. The roofer said it's not needed, would increase labor & materials substantially. So I am NOT going to have them lay plywood.

BTW just took a closer look at the planks they are 3/4in x 7in wood (not sure what kind).

Thanks again
Hammer


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PostPosted: Mon Sep 25, 2006 7:59 pm 
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I know this is a dead post at this point but i want to put my 2 cents in. 3/8 plywood i wont use. Just too flimsy. I tear out i dont know how many 3/8 decks a year so 1/2 is my starting point if im using plywood. as far as clips are concerned i agree with the 8d nail but code rquires on decks out here to use clips so im stuck suing them. Atleast there is not a buckled sheet on the roof after.

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  Post subject: Re: No Plywood Under My Shingles!
PostPosted: Sat Oct 28, 2006 8:55 pm 
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hammerdown wrote:
This home was built in 1953. I purchased it in 1999. I am getting ready to have the existing three layers of shingles torn off and a fresh new roof put on :)

I am also having a central air system put in, and I ripped up a 5x5 ft pad where the unit will sit. When I got all three layers off, I was surprised to see that underneath there is not solid plywood but slatted like 1x4in planks! I can see right through into my attic :shock: And the planks don't seem very strong, like I could put my foot right through them. So...

What are the advantages/disadvantages of having this type of roof? Could I, should I have the roofers slap new plywood over the planks?

Hammer
Nothing wrong with 1x4 sheathing board save your money


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  Post subject: if 90 percent of the boards are
PostPosted: Sat Oct 28, 2006 11:32 pm 
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in good shape repair the ones needing work. Sometimes there will be weak areas cause it is a poor grade of pine and you may get a large knot that breaks out between rafters. Most of my whole roof was loose cause of expansion and contraction. Stapling made it very tight and strong.

A solid wood roof can leak alot before the wood is damaged. In this case cause it is pine it is fine to reuse it and it was leaking for a while. If it had been plywood and leaking the plywood would be toast.

Because this home was plugged and cold not breath there was mold on the spruce but non on the pine, there is a resin or something in pine that resists rot fairly well.

I know didly squat about roofing and have learned the tiny bit I have here. with thanks. I checked with Certainteed and you don't have plywood over, it is not required, it may be recommended but it is not required. Comfortable enough to accept that from them.

If your boards were wide like 7-10 inches they should be ripped and they do recommend that. Use a cheap cheap rip blade and wear a face shield cause there is going to be shrapnel.


Warren


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PostPosted: Sun Oct 29, 2006 8:57 am 
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Warren, how is that roof going on that house? Did you get it done?

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