Help: Need advice on roof decking.

[mannyrock]

Dear Guys,
 
   Here's the facts.  I have a ranch style house, 30 years old, built with pre-made trusses (2x4s) spaced 24 inches apart.  The original decking was just 1/2 inch plywood.
 
   After 30 years, about 10 sheets of the plywood are soft and stained from occasional leaks and repairs.  Other sheets of the plywood "sag" between the trusses (as you come down the roof walking between the trusses) because the morons who originally installed this roof were not careful about installing the metal edge plywood clips exactly half way between the dead space between the trusses.  In some instances the clips were installed with about 16 inches of distances on one side of the clip and 8 inches of distance on the other side, with the result being that the unsupported 16 inches of plywood seam edges eventually sagged downward from the weight of snow and lack of support. 
 
   There are currently two layers of shingles on this flimsy roof.
 
  I have a contractor lined up, ready to pull all of the shingles and tar paper, and pull the 10 sheets of water damaged plywood.    In order to keep things consistent, the damaged plywood will be replaced with brand new 1/2 inch EXTERIOR grade plywood.  I would love to replace it with 5/8ths, but my roofer said that it wouldn't line up with smooth edges against the existing 1/2 inch decking, and this would create horizontal lines that would be visible through the shingles and create a tendency to leak.  (Personally, I find it hard to believe that a mere 1/8th inch difference between the thickness of the sheets side by side could be so dramatic, but he is firm about this.) 
 
  After this, the entire roof will be be re-roofed with ice-guards and architectural shingles.
 
  Here is my question.  I do not want to spend the extra money, and damage to the underlying 2x4 trusses, to have the entire deck of old plywood ripped off and replaced with a new plywood deck.  But, I was thinking that after the 10 damaged sheets are replaced, I might consider having a SECOND layer of decking screwed down on top of it, made of the cheaper 1/2 inch OSB.  The new layer would overlap the seams of the old plywood, and would (I hope) smooth out and strengthen the roof as a whole.)  I guess that I could also pay to have each new sheet of OSB covered with structure adhesive before it is screwed down, to make the deck extra firm.
 
    No nail guns will be used to fasten down decking.  Only Sencdo duramax exterior weather-coated roof decking screws, approved for use in Florida against hurricanes and weather.  My trusses are so dry, that a nail gun will shatter them.
 
 
    I would welcome advice on my idea of adding the second layer of OSB.   I will probably only live here about another 10 years, so is it really worth it?   Is it OK to put OSB on top of plywood, or is this a mechanical no-no?  Is it worth it to glue the new OSB down, or is this wasted money. 
 
     Thanks for all advice.
 
Best Regards,
 
Mannyrock
 
    I have a contractor lined up to pu
 
 
 
 
 

[mannyrock]

 
  P.S.-  The second layer of decking, OSB, would go over the entire roof.  Not just the 10 sheets of replaced plywood.

[hunt-m-up]

If you were in an area that has a snow load the extra weight of the OSB would be a concern in addition to the weight of the snow, but doesn't sound like snow is an issue. Does it meet code in your area?  Wouldn't think 1/8 would be an issue, we see nearly that much variation in thickness on roof decking from one sheet to another on new sheathing anyway.

[briarpatch]

With the three tab shingles you would be able to see the difference in height after a few years in the sun. They get hot and flow to the lowest point. With the thickness of architectural shingles I dont know.
I reroofed my roof with 3/4 plywood and with all the homes going up with 1/2 inch I dont think it was worth it for me. I used a nail gun and my home was built in the early 60's here in Florida. I have never seen trusses to dry but Ive not seen yours.
If it were me I would use the same thickness and slide the clips closer to center when it is cleaned off then add shingles and move on.
When you start piling stuff on top of stuff it can sometimes be worse than nothing.

[PowPow]

If you are trying to get rid of the "scalloping" between joints, seems like you could scab a 22-1/2" 2x4 underneath the joints to flatten it out, maybe only on the worst spots.
Before I did that, I would try to slide the H-clips to the middle and see if the fixed it. Probably with a light hammer and a thin piece of metal, like a metal ruler.
Hurts my back thinking about it.
 
Our building inspector is helpful critiqueing ideas like this, especially if your intent is to exceed codes rather than skimp on them.
Yours may be too.

[scootrd]

Dear Guys,
 
   Here's the facts.  I have a ranch style house, 30 years old, built with pre-made trusses (2x4s) spaced 24 inches apart.  The original decking was just 1/2 inch plywood......
 

Manny ,
I feel your pain. Wife and I just went through this last year. Leaks were abound , Builder use cheapest roof construction possible. scalloping was just getting worse and worse. I finally had it.

In the for what it's worth category.
We went thicker sheathing , skipped the old tar paper crap , went with Snow and Ice under-layment all the  way up , and a reasonable 25 year shingle. Made all the difference. Have never slept better. outlay of cash for new sheathing hurt a bit but I chalked it up to short monies recouped by a better nights rest Not worrying as much about snow load, Ice dams, and further ceiling damage, especially with spring rains right round the corner.

We looked at metal roof , (my sister has hidden seam and we like the look) but just couldn't justify additional costs , as we will not be in this house when we fully retire. We will down size to smaller ranch , big barn , additional acreage. Will save the metal for final smaller house. 

[Larry L]

This post is more to inform you rather than any direct advise. I have over 30 years in the lumber business and am past President of the Alamo Area Lumbermans Assoc. So I kinda have a clue about materials. In regards to the ply clips. If you look real close at a ply clip, you'll find a barb looking affair on the center bar. The purpose and function of a ply clip is to properly space plywood so that it can expand and contract. It's not there to provide rigidity or to eliminate any sagging between joists. Because you have sagging, apparently, between joists, are you sure that the material is 1/2"? When your house was built, a lot of the builders used 3/8 plywood as it would span 24"OCs for roof decking. But most local codes no longer allow it as the carpenters were notorious for putting a knee on each side of the joist and nailing a sag in the decking. Todays 15/32 plywood is rated at 32" OCs for decking and should make the 24" span easily. There is no need to add another layer of decking as the additional weight might go past the limits of a 2x 4 chord in the trusses, especially with a snow load. Generally speaking, a 2x 4 truss of the era was built with 1550F yellow pine and was designed for a 10lb psf load limit. Figure the normal square tab shingle, felt, and roof decking of 1/2 plywood and you're at 4 lbs load. That only allows for 6lbs of snow load- that's not a lot.
I think it's important for you to know that any plywood with a D face, like CD grade, is an interior rated product. The normal CDX grade is made with exterior glue but will not stand up to continued exposure. It's limited as to how long the exposure to the weather and that's usually about as long as it takes to deck and roof a house. OSB is made with an exterior rated epoxy and will hold up far longer under wet conditions but the span rating for it is only 24" for 1/2" nominal material. So be careful as to the materials being used. The grade stamp should read "Exposure 1" for plywood roof decking. "Exposure 2" would want me to have it removed as it won't stand much exposure at all.
If you are considering moving in 10 years, why spend the dollars on an architectural roofing material? They weigh more than the normal square tab and you may already be at the limit with the 2x 4 trusses. All of our trusses here are now 2x 6 chords and we don't have snow load allowances. Unless the trusses have load points, I'd stay away from a heavier roof material. And unless you're a very experienced carpenter who has installed thousands of these trusses, you're not going to know if they are point load or not. You could hire a structural engineer but that's more money spent. Just pointing out you may be exceeding the design limits of the trusses with a heavier roof.
And one last thought for you. I don't know if this is the norm where you live but in Texas, most roofers, as in those actually on your roof hammering the nails, have been in jail and I don't mean for traffic violations. It requires no special skills. Only to be able to stand the sun and heat during the summer. Most businesses will not hire these folks because of their prison records. Keep any indication that you have guns, jewelry  anything of major value hidden from these guys, especially guns. Just because a guy has worked for ABC Roofing Co for years doesn't mean he hasn't been doing things on the side that would put him back in the pen. Deer mounts on the walls that can be seen thru a window/door, gun racks in a truck, a hunting buggy, all need to disappear when these guys are working there.
Hope this has some value for you. Here's technical specs on plywood.
http://www.plumcreek.com/Portals/0/downloads/productInfo/J20.pdf

[Ranger99]

^ ^ ^ ^ ^ ^ ^
read this last part of L.L.'s post several times.
sad but true

[FPH]

L.L.'s advise is spot on.   After working as a roofer while going thru college.......there are a lot of shady characters in the bus.

[briarpatch]

You can say the same about most people that work residential. No drug testing/back ground checks and better pay than mcdonalds. Its where those that cant make the background and drug test for commercial and industrial go.
A lot of the companies that hire them probably dont have workers comp or insurance. If one of the illegals falls off your house guess who pays? The home onwer is responsible for the care of the hurt worker.
Dont just take their word for having the proper paper work, check with the state, most places on line and they can give you a run down on who is and who aint.

[hunt-m-up]

What Larry meant to say was it requires no special skills if you don't mind a leaky roof, a few tabs flapping in the wind, and your stuff missing. And what is this hammer you speak of for roofing? 
About the same time they were using that light sheathing stapling shingles was also quite popular, crap all the way around. Not sure why ice and water shield or whatever brand you use is required all the way up the roof, synthetic underlayment will provide very good protection. I would spend the money on all new sheathing and stick with 3 tabs if it were an either/or situation.

[FPH]

Ask for certificates of insurance for both workers comp.( you at least need a letter of subregation) and general liability     ( make sure you are listed as additionally insured). On a remodel, you also need builders risk ins.   Or you need to check with your home owners ins. to make sure you are covered. I carry a minimum of 1 million on worker comp. and 2 million in GL.  Also, I would never give anyone any money down.  If the contractor isn't big enough to front the money for the first 30 days and wait for a draw, I would send him down the road.  If you are in TX, a State lic. is not required.  However, some cities in TX do require a local lic.( ins. will have to be shown).  If you are in a State like NM, a State lic. is required.

[scootrd]

If the contractor isn't big enough to front the money for the first 30 days and wait for a draw, I would send him down the road. 

Not disagreeing with a single thing you said, and perhaps maybe I have been just lucky however I have always worked with contractors on a 1/3 draw at time of materials delivery on site, 1/3 draw half way through completion , and 1/3 upon final inspection.

So far it has served me well in life.

[PowPow]

Hope they don't drag a roofing job out long enough to make draws necessary.
Our house is a ranch, 5/12 pitch over 2000 sf floor space; took 3 days to take 3 laters off and put new back, along with new vents.

[45-70.gov]

my  house  and a few 100 others  i built over the yeas  is the same roof as yours


i have switched to metal  roofs  on 6 of my houses


it is best to put strips  down  but you can screw straight to the ply wood
i just  leave the old shingles  up there


metal  is cheap and fast..........AND I LIKE  IT
THE LAST  METAL ROOF  I DID WAS 4 MONTHS AFTER HEART SURGERY
SO  ITS  NOT THAT HARD TO DO

[FPH]

If the contractor isn't big enough to front the money for the first 30 days and wait for a draw, I would send him down the road. 

Not disagreeing with a single thing you said, and perhaps maybe I have been just lucky however I have always worked with contractors on a 1/3 draw at time of materials delivery on site, 1/3 draw half way through completion , and 1/3 upon final inspection.   

So far it has served me well in life.

Just make sure you can justify the material supplied and labor done before you write a check.  I've seen too many people screwed by giving too much down.  Three days sounds about right for the amount of work you describe.  You will want a written lien release and warranty,

[mannyrock]

Dear Guys,
 
   Thanks for all of the great advice.  A couple of points:
 
   1.  I will never allow plywood to go down on my roof unless it is true Exterior Grade, B/C, one side sanded, hand picked by me.  Yes, its almost $20 per sheet.  But Group One is trouble and CDX is total crap.
 
    2.  Another guy giving me an estimate also wondered whether or not my roof may only be 3/8ths instead of a true 1/2.   I believe I measured it with a caliper and it was just barely below 1/2.  It has four distinct veneer layers, so I'm really hoping it is dimensionally 1/2 inch.
 
   3.   I have decided to go with architechural shingles because we constantly have high speed sheer winds in this area.  I live in the Shenandoah Valley, but right next to the Luray Pass, which cuts eastward through the Blue Ridge Mountains.  I think this creates some type of funnel effect, which concentrates the wind blowing from out of the West into a narrow corridor, coming right over my house.    About 3 times a years, we have these high wind storms, and the next morning, all of my neighbors and me are out in our yards picking up big sections of three-tab that have just been torn off of our homes.  Even people with brand new roofs!
 
   4.  My roofer told me that the Architectural shingles, being of different dimensions and thickness, will help to  hide the scalloping a little, whereas the flat 3-tabs will accentuate it.
 
   5.   I may try to fix some of the scalloping by pushing up and fastening 2x4 cross sections under the scalloped seams, but since the plywood itself is 30 years old dry, I'm not sure that I will have the strength to push them upward and hold them there while I fasten the cross pieces.   My brother tells me to put a 2x8 across the bottom chords where I will be standing, and use a car jack (sitting upon it) to "jack-up" the low place while I am working to fasten the cross piece.  This sounds pretty dangerous to me, but he swears that roofers use these  all of the time.
 
  6.  Having worked as a construction laborer for 3 summers while in college, I got very acquainted with the career criminals who worked in the ditches and on the crews.   They were not minor sociopaths or committers of petty crimes, but were true career felons, always scheming about how to steal a tractor, or a piece of equipment, or even just a hand tool that was laying about or unguarded.  A common phrase was "we'll come back at night and [fill in the blank.]"  Most had been in prison for a violent offense, such as assault and battery, even manslaughter.   So I agree, I have to be real careful about this. 
 
   7.   I too worry a bit about the extra weight of architectural shingles, but since it will be the only layer of shingles up there, I am hoping that it won't be an issue.  I'm not putting ice guard over the entire roof, but just in a few normal places under the overhangs.
 
   8.  The trusses are made of southern yellow pine, but believe me it is not what its cracked up to be.  Yellow pine timber is full of large knot-holes, some of which are two-thirds the width of the board itself.   I have about 5 cracked or totally broken chords up there now, all stemming from the dried knot holes, which I am repairing or replacing with triple pieces of straight grain, super premium, no-knot-hole, hand-picked white pine 2x4s, all screwed and glued together with the PL 8x premium structure adhesive.  You can't even buy yellow pine in 2x4s around here anymore.  It's only comes in 2x8 and up.
 
    9.  I will NEVER buy a house with pre-fab trusses again.   My parents house is 60 years old.  The rafters are solid one-piece 2x8 lumber and the decking is 3/4 true exterior grade plywood.  It is as solid as concrete and you could  land a helicopter on it.
 
  Thanks for all additional comments.  I am really worried about all this.  I always try to do a totally first rate job on any house repairs.  Obviously the best thing would be to have the entire deck ripped off and replaced with new plywood.  But, for just the repairs and reroofing I have mentioned, I am already up to $13,000.   I'm pretty sure it would top $20,000 to redeck it all.  Plus, who knows what extra damage would be done to the trusses by the guys ripping up all of the decking?
 
   My brother hates the way I pour money into my house.  His attitude is, "So what if the roof sags a little?  SOMEBODY will buy it.  You just keep lowering the sale price until they do."
 
Thanks for all any additional comments.
 
Mannyrock
 
   4.   
 
 
 
 

[45-70.gov]

i am with your brother


the arcetectural shingle will hide the sags better
and  are better shingles


but not near as good as metal
nothing wrong with truss  they are engineerd to  be stronger than a stick frame roof

[superd]

Being a contractor I do not front money/material after being taken advantage of by homeowner/builders. I now get my pricing and present homeowner/builder with that quote and have them pay the driver directly, I am not a delivery service as most do not want to pay my time and costs for such activities. This also does not waste my time if a homeowner wants to handpick material, I am usually on deadlines and cannot wait on the homeowner to pick through lumber. I also hire a cleaning company at the conclusion of the project since so many homeowners are afraid of any post construction dust these days.

[mannyrock]

Dear Guys,
 
    Thanks for all of the great advice.
 
    I have decided to go with the following:
 
    1.   Just replace the badly damaged deck sheets with one-half inch true Exterior grade plywood.  It will probably be 10 to 15 sheets.  These will be screwed down.   
 
     2.   Put down the architectural shingles.  I understand that they are 50% heavier than 3-tab, but since two layers of 3-tab are being torn off, the resulting roof will actually be lighter.
 
      I guess I will just have to live with the areas of scalloping.  They were there when I bought the house, and I think that the architectural shingles will help to hide it alot.   My emotions tell me to have the entire decking ripped off and redone to the whole house, but my rational brain says no.   Too much money, and too much trauma, to the structure and trusses as a whole, basically just to clean up a few visual annoyances.     Twenty years from now,  when the new shingles wear out, the owner can then decide for himself what to do.
 
   My problem doing carpentry is that for me, the only acceptable solution has always been perfection.  "Workmanlike" or "good enough" makes me unhappy.   (When I do work for other people, it is always perfect, and I sign and date the work inside the wall when I'm done.)    However, it is clear to me that the building industry, including materials, tools, skills and training, is never geared to perfection, only just good enough.  So, trying to get any contractor or worker to do anything better is almost impossible.  They don't know how to do it.  And even if you are willing to pay them to do it, they are incapable of figuring it out or altering their mindset.   
 
      I am constantly stunned as to how truly ignorant general contractors and repairman are as to first rate materials, such as true APA exterior grade plywood, heat treated structure screws, PL 8x construction adhesive, Geocell 50 year tri-poly exterior caulk, etc.   They have never heard of them.
 
   They are all about CDX, nail guns, and toe-nailing lumber with 12 or 16 penny nails, regardless of how much splitting, shattering or damage to the existing lumber it does.  So their "work" looks good for about 5 years, and then turns to total crap.
 
    Thanks again.
 
Mannyrock
 
   

[FPH]

Dear Guys,
 
    Thanks for all of the great advice.
 
    I have decided to go with the following:
 
    1.   Just replace the badly damaged deck sheets with one-half inch true Exterior grade plywood.  It will probably be 10 to 15 sheets.  These will be screwed down.   
 
     2.   Put down the architectural shingles.  I understand that they are 50% heavier than 3-tab, but since two layers of 3-tab are being torn off, the resulting roof will actually be lighter.
 
      I guess I will just have to live with the areas of scalloping.  They were there when I bought the house, and I think that the architectural shingles will help to hide it alot.   My emotions tell me to have the entire decking ripped off and redone to the whole house, but my rational brain says no.   Too much money, and too much trauma, to the structure and trusses as a whole, basically just to clean up a few visual annoyances.     Twenty years from now,  when the new shingles wear out, the owner can then decide for himself what to do.
 
   My problem doing carpentry is that for me, the only acceptable solution has always been perfection.  "Workmanlike" or "good enough" makes me unhappy.   (When I do work for other people, it is always perfect, and I sign and date the work inside the wall when I'm done.)    However, it is clear to me that the building industry, including materials, tools, skills and training, is never geared to perfection, only just good enough.  So, trying to get any contractor or worker to do anything better is almost impossible.  They don't know how to do it.  And even if you are willing to pay them to do it, they are incapable of figuring it out or altering their mindset.   
 
      I am constantly stunned as to how truly ignorant general contractors and repairman are as to first rate materials, such as true APA exterior grade plywood, heat treated structure screws, PL 8x construction adhesive, Geocell 50 year tri-poly exterior caulk, etc.   They have never heard of them.
 
   They are all about CDX, nail guns, and toe-nailing lumber with 12 or 16 penny nails, regardless of how much splitting, shattering or damage to the existing lumber it does.  So their "work" looks good for about 5 years, and then turns to total crap.
 
    Thanks again.
 
Mannyrock
 
   

Welcome to the world of residential contracting.  I mainly have done commercial work and have had my eyes opened when I did a project for a engineer friend at his home at his request.  I have a reputation for quality workmanship and finishes, but the subs lackadaisical attitude in residential just about blew me away.

[mannyrock]

 
  Here's what I've started doing to weed out incompetent "carpenters," and it has helped alot.
 
   Firsts, I ask them  on the phone whether they are a certified Journeyman or Master Carpenter.  An overwhelming majority of them will tell you on the phone that they are.  If they tell me that, then I tell them that they will need to bring their certification papers to the job.  If they don't have them when they show up, I know they are liars and I fire them on the spot.
 
   Next, I ask to see their tools.  (My two uncles were old time carpenters, and they always had three full toolboxes full of every conceivable hand tool any carpenter would ever need.  They carried their power tools in the trunk.)
 
   Lots of them will show up for a complicated carpentry job with nothing but a hammer, a few boxes of nails, a circular saw, a tape  measure and a nail gun.  They don't even have a level.  (I kid you not!)  I fire them on the spot.  I tell them that I'm hiring a carpenter, not a house framer, and since they don't even  own a set of carpentry tools to bring to the job, then they plainly aren't carpenters.
 
   I think that the number one reason that residential carpentry repairs are so bad today, is that the average house gets sold every 7 years or so.  It's not like the old days, when people owned their houses for 25 to 30 years and actually cared about the quality of the repairs.  All they care about now is that it look OK for a few years, until they dump it off to someone else.
 
  Thanks for all of the roofing advice.
 
Best, Mannyrock
 
 
   
 
 
 

[FPH]

When I still wore my tools and was a carpenter in TX, I was never a Union carpenter.  I didn't know anyone who was (and I knew some good craftsmen.....both rough and finish)  I did have a trailer full of tools and carried GL and Builders risk insurance ( I would be asking for those......most "tailgate" carpenter don't carry that).  I did work along side some Union carpenters on A&M's stadium expantion......talk about slow.......never worked by the job a day in their life.  Just because your fast, doesn't mean your not good.....might just mean you know what you are doing.