Proper Redecking Practice, plywood over 1x4


#1

I just had an old house reroofed including redecking the entire house. The original decking was spaced 1x4s. The roofers removed the old shingles, shakes, and nails and laid the new 1/2" plywood over the 1x4s. They did not take care to make sure than the edges met on 1x4s and made no attempt to hit rafters w/ nails.
But my real question is this: when you redeck over existing decking you necessarily raise the height of the deck by the thickness of the new decking, in this case 1/2". That means that the decking is no longer flush w/ the fascia boards or crown moulding as the case may be. The edge of the plywood is visible. Is this standard redecking practice and what do you do about the exposed plywood?

Bill
Memphis


#2

We always run flashing up the gables to hide the plywood.As far as sheets not hitting the 1*4’s thats just a hack job,they should have been cut to land on them.And trusses should have been chalked out so they were nailed into as well.


#3

Sounds like a hack job to me also.


#4

Hi,

You do not need to hit the rafters. The 1x4’s are moved up to hit the joint of the plywood.

Chances are you will have no problems with the way it was done. The 1x4’s are close enough together that the plywood should lay flat. This is why the guy cut corners and did not move the 1x4’s. You may want to get a couple of bundles of shingles if any of the plywood buckles. It is rare but does happen.

The guy who put your roof on should have use an edging to cover the plywood.


#5

Yeah, I’m gonna have to agree with Lefty on this one.

I like to cut new 1x’s & install them vertically on the existing rafters so that you get a fully flush roof deck with ALL the 1x’s; that will prevent (or @ least slow down) any overdrive on the decking nails or staples that are used to attach the roof decking.

As for the rakes & eaves, yes - some sort of a block or gap insert should have been used. It is also common to have an oversized or longer faced kind of drip edge to conceal the gaps.

Can you post any photos for us? If no actual photos, how about the links & then I’ll fix the “url” for you soas to embed pics in this thread.


#6

The horizontal seams on the plywood don’t need to fall on the underlying 1" x 4" material.
The vertical seams need to line up on the truss’s/rafters.
1" x 4" skip sheathing won’t hold the nails very well for very long and in time you are likely to see the seams in the plywood as they start to loosen up.
You will have loose decking and nail pops where the vertical seams are not centered over the truss’s/rafters.
I see it all the time…

We use a drip edge/gutter apron on the eaves and a drip edge on the rakes on all buildings unless it is an architectural detail of the building not to have it.
It is common practice in my area to do so.


#7

I like to rip my first row to land on the skip-sheathing,and the rest of the rows usually then work out and land on them also.Just how I do it.Ditto Axiom on everything else…


#8

The horizontal gaps aren’t wide enough to worry about, unless you are talking some extreme widths.

But, I disagree with the other guys about not landing on the rafters with your vertical edges.

I am sure they at least nail the sheets properly, but I have seen way too many other contractors re-decked jobs over skip sheathing pop up at the 4 foot vertical seams, which either indicates a lack of nailing, which should be every 6" OC, or that the depth of the nail did not penetrate the skip sheathing enough, or that the skip sheathing does not have the same holding power or an 8 penny nail by itself.

Chalk line all the rafters and trim to split the center of the last one, in my opinion.

Ed


#9

I have to agree that the plywood joints should be centered on rafters, being its nailed into 1 bys instead of plywood may be somewhat stronger but its just not the same in strenght as it would be if the joints was nailed in the rafters and it may pull loose in a few years.


#10

is every one forgetting the # 1 cause of plywood popping? Not using ring shank nails! 8)


#11

It’s all I use. No staples here…


#12
I remember reading somewhere in the building code the specifications for sheathing nailing and where the joints are required to be backed up, but I can't recall what it said because I decided to just pull off my old split 1X8 boards and nail new plywood directly to the rafters...Dave

#13

The nailing pattern is 6" OC on the end vertical edges on the rafter and 12" OC on the interior covered rafters from the sheathing.

Ed


#14

I need to double check from underneath but I’m not sure they even made much attempt to hit the 1x4s - they just eyeballed it and hoped that enough made contact. And, yea, this is 100 year old 1x4 decking and it does not hold all that well, and splintered in many places.

So, does everyone agree that there should be no exposed plywood, even edges? Should that have been spelled out in the contract or is it just assumed as part of good practice?

I’ll take some photos and see if I can post them.

Bill
Memphis


#15

we overhang plywood 1/2" for gutters.


#16

Drip edge should have been included in the scope of work.
I have seen a few jobs that I bid on,(done by others)that had no new drip edge,no ridge vent,and some were even over the top on jobs that the owner was made aware that the plywood was in need of replacement(from lack of vent…)and still have no vent…
It seems that most are out to get the lowest cost job…while I still get my share of the ones that want it done right…I am still scratching my head on the ones that I have previously described…These are the ones that will also tell their friends how the roofer screwed them,lol
It seems to me that guys are lowballing to get the job,and just not giving what they should in the job…cost are rising,and guys seem to be using less materials on the jobs…
1 estimate I did the lady asked if Ice and water shield was extra,lol…as if it were optional…lol,am I missing something here?
Also it takes pride and patience to cut the sheets to land on the rafters on an old house where the rafters don’t fall on a 16"oc.(or any kind of layout)and it is easy to criticize anothers work,till you are the guy who bid the job with the thought of sheeting it in a day,and then you get up there and it takes 2 days cause you have to cut every sheet…(I know every one can identify with that feeling)&$^&%&&…!I have already went to a H.O., and explained how in this case it would cost a little more to cut all the sheets to get the proper nailing,and they usually agree to pay the difference. Most of the time when people have a very old house,they know that the things that they want to do to modernize cannot be done conventionally…


#17

http://www.roofing.com/images/topics/6929/img_1223742683.jpg
http://www.roofing.com/images/topics/6929/img_1223742284.jpg


#18

I wouldn’t be happy with that workmanship at all.From the couple of pictures you posted,it looks horrible.The edge isn’t even nailed,imagine what you can’t see.


#19

They brought the plywood down to the crown (in some places flush, some overhanging, and some behind) and nailed it to the first 1x4. BTW I paid over $12,000 for this job.

I’m still somewhat confused over what the proper edge treatment should be when you redeck over existing 1x4 decking.

What I am going to end up doing is tack strips of lattice moulding to the top of the crown to cover the plywood edges. When caulked and painted it will look like another profile of the crown. But IMO I should not have to do that.

Bill


#20

[quote=“bldn10”]

What I am going to end up doing is tack strips of lattice moulding to the top of the crown to cover the plywood edges. When caulked and painted it will look like another profile of the crown. But IMO I should not have to do that.

Bill[/quote]

I think I would try some eve metal, as long as it will cover the gap . You can have it made to your specs if needed, just slide it under the shingles and nail it. It may take two people on ladders to do the bottoms, one at each end. I think it should have been done at the time of the install by the contractor.