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I’ll take a wild guess here and figure it’s your own roof,
since you’re not a roofer. I’m always amazed at anyone who
does not strip their own roof first. What’s the big deal? I
bet it wouldn’t take you, by yourself, a whole day to do it
(I don’t have enough info from you to back that up) but why
wouldn’t you want to strip the old shingles?
Some roofers don’t do it, but you can bet that they do on
their own houses.
But the benefits of stripping far outweigh the small task of
doing the work, especially with your woven valleys.
No, if you put the shingles over the old shingles, you don’t
put any felt over them.
Hope to help,
MD
xxxxxxxxx
Replies
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A lot of good advice, Stephen and Mike. Glenn, you'll have
to judge for yourself if adding a layer is what you want for
your roof. I think all that heat and humidity is a problem
for the double layer idea, could really cut into the life of
your roof (it would either way) but at least you don't have
a snowload to worry about, as per Andrew's weight concern.
I hope you didn't think I referred at all to you, Ryan, but
your post seemed like maybe you did. Your advice is good
too, if the shingles are cupped or in otherwise poor
condition, it wouldn't make sense to put anymore shingles
over them.
Well, good luck. It'll probably be a good experience for
you. Just don't take a slide, that's number 1. Number
2-don't take the big step. No. 3, don't walk on loose
tarpaper or loose dirt,leaves,sawdust, etc. It just goes on
and on with safety. As long as you don't hurt yourself, the
project will go allri
*
No offense. My shoulders are broad.
When I said "I want to learn something", I really meant it.
*
I will be installing a new roof over an existing roof(single layer).
The existing shingles are of the standard 3 tab design and I am thinking of installing the Timberline(?) type of shingles.
Should I install directly over the existing shingles or should I install felt paper first?
Also there is only 1 valley of about 14 or15 feet to deal with and at the moment it is an interlaced or platted valley. Does that type of valley work with the Timberline type of shingles or should I install valley tin and cut the shingles in the valley? Personally I like the cut look with the flashing showing. What is the rule of thumb for the width of the cut from top to bottom? I know its wider at the bottom than the top but not sure by how much. How wide of flashing and what type of flashing should I use? Aluminum? galvanized? Rolled? Sheet?
I would also like to know if installing a ridge vent would be advisable. There are only two ridges and one is over the garage and the one that is over the dwelling is only about 8 feet long. The roof is all hip with no gables.
I live in Houston TX if that makes a diffrence to which way I should go on some of these things. High humidity.
Any help would definitely be appreciated.
Thanks
glenn
*Strip off the old roof. Check the sheathing, put on new flashing, felt, and re-do the valley as well, follow the instructions for the architectural shingles as to how best to construct the open valley. Usually, they are cut 3 inches to either side of the centerline, and not varied along the height. In Texas? I'd be checking with ELK for my shingles.
*Code in your area probably allows two layers of shingles. If your sheathing is in good shape (walk the roof and check underneath if you can), and if the shingles aren't so cupped that a second layer won't lay flat, a seclnd layer is fine.Remove any badly cupped shingles, Don't tarpaper again, install each course of shingles so that the top edge buts up against the bottom edge of one of the old courses and the roof will lay the flattest. (That means that your first course will have less exposure than the rest).Use Aluminum in the valley and if you have a steep pitch, bend our aluminum with a short bump down the center. This will slow water down comming down one roof and stop it from rushing up under the other roof.As for venting in a hot humid climat: I think it's a good idea but ridge vents are no good without soffit vents to let the air in. (Wait...you're gonna get 10 different opinions on the venting)
*Im with George...strip off the old shingles first. Its more work, and more money if you arent doing it yourself, but well worth it in the long run. In the valley I would run ice and water shield down the length of it. Put your metal over this if you want the exposed metal look, and definitly bend.
*I'll take a wild guess here and figure it's your own roof, since you're not a roofer. I'm always amazed at anyone who does not strip their own roof first. What's the big deal? I bet it wouldn't take you, by yourself, a whole day to do it (I don't have enough info from you to back that up) but why wouldn't you want to strip the old shingles?Some roofers don't do it, but you can bet that they do on their own houses.But the benefits of stripping far outweigh the small task of doing the work, especially with your woven valleys.No, if you put the shingles over the old shingles, you don't put any felt over them.Hope to help,MDxxxxxxxxx
*I'm not a roofer. I do a few new roofs on rooms I build but I stay away from reroofing just because I hate to do it. I don't have the patience to lay shingles all day.I'm not arguing, just trying to learn something.What's the advantage of tearing off?
*>My understanding is that a nail-over/2nd layer won't last as long: some folks have said up to 5 years less life because of more heat buildup in 2 layers. (Others say there's no differnece.)Also, one layer looks a lot better than 2, IMHO, but 99% of folks don't know the difference. I have seen a couple roofs where I couldn't tell there were 2 until I pulled up the drip edge to peek. (Exciting life, eh?)Bob
*Yes, I beleive code will allow 3 layers, but that I wouldn't do. The reason I wanted to just lay over the existing roof is because of time. I suppose I could strip in sections and roof that section etc. etc.Also if I were to strip, where do you get those large tarps to cover the unfinished portion? thanksglenn
*There is a weight issue for some older house -- I just did a 50% tearoff and it really adds up. Because I'm taking the sheathing off too, I do get the benefit of not pulling out all those damn boot-piercing nails. It is definitely lunkhead work, nothing glamorous about it.On our 12/12 roof, it was pretty aerobic. Fortunately I had a helper collecting the crud and tossing it in the dumpster. Nailed-on 2x4 cleats were plenty for traction.Q: On a closed valley, is there any flashing (other than the membrane or roll roofing)? What's the benefit of an open valley? Will the open valley shed decomposing leaf litter better?And glenn, I'd recommend a tear-off too, it's the only way you can be sure to find all the rot resulting from the idiot who flashed the last job and messed up every penetration. This guy used the black-gunk-and a-prayer on the chimney method. And why does everyone feel this compulsion to put nails through the exposed bottoms of stack boots? I -know- it looks like there should be some nails there, but duh... Sorry, I'm ranting...
*IMHO: Another reason for stripping is so you can redo the flashings, if any. So, longer life, inspect your roof deck and nailing, better looking.Strip it off. Strip what you can paper in the same day.Paper in with either 30# felt, or even better is Certainteed's Roofers Select..strong and doesn't wrinkle.You buy the big blue tarps at any good hdw. store.Look at Certainteed's shingle line. Timberline is good, but GAF hasn't really kept pace with the rest of the industry. Elk has a bad rep. around here, check at a roofer supply store that carries different lines.Think about a California cut for your valleys, the lower roof extends thru the valley, and the upper roof gets cut to a neat-line you snap from top to bottom. If you use a metal valley, aluminum with a standing seam in the middle is a good choice, over a 3' piece of ice and water. I like a tapered open valley, apx. from 6" to 8". If you have corrosive enviornment, think about lead-coat copper. Most mfr's. don't recommend OPEN valleys, but if that is the look you want, then it has to be a metal valley, and there are some tricks you should know about metal valleys that are beyond this scope.Read and follow the MFR's instructions on the wrapper.Houston may require high wind nailing. If you want a long life shingle rated for 110mph, with an algicide, that looks like a slate, try Certainteed"Hatteras".Hatteras and all of the Architectural shingles require a special hip and ridge shingle for the caps.Use Shingle Vent II shingle over ridge vent, wether you have soffit vents or not, you may add soffit vents now or later.Use an ice & water membrane in your valleys and along your eaves, its the best and cheapest insurance you'll ever buy.Use a metal drip edge (alum or copper) on eaves AND UP THE RAKES, your rake boards will thank you for it.Snap lines and layout for center so your left and right edges will be the same (if there is only one edge on a particular roof, lay out from that edge). Snap lines at least every 5th course, and when you get about 10 courses from the top, check your measurements and adjust for parallel to ridge,, to adjust, shorten your exposure , NEVER stretch it. Also adjust so you can avoid a one or two inch course at the top.Use only HOT DIPPED galv. nails (hand nails) or if you are using Guns, try Paslode, they seem to have the best corrosion resistance.Go for a 40 year shingle, you don't want to be doing this again if you can avoid it. Just think about what you're going to have pay some young dude 20 years from now.Get some help, this is heavy labor.Stage it safe, set a stage 3' below your eave on any section you're working, you'll get a better job, you'll work faster, and you'll avoid broken limbs.b Lets be careful out there, this is the chance to work off that beer gut.
*It seems we have had this discussion countless times before,but I will shoot my mouth off on it anyway.If the existing roof has 1 layer and the wood is sound there is no need for a tear-off.If you can inspect the decking from underneath,and walk the roof from above and everything checks O.K. I would feel confident in going the layover method.As a roofing contractor ,I find in my area that most of the wood replaced following a tear-off was necessitated by the tear-off itself.Many of the houses here are of older vintage,sheated with #2 or #3 1x8. Lots of little nooks and crannies around eaves,chimneys,valleys,waste stacks etc. where short peices are used.These have a tendency to split and disintegrate when the existing roof is torn off.We do tons of 2-3 layer tear-offs and the extra nails in those situations only compound the problem.Even in the case of tearing off a plywood decked roof, significant damage is sometimes caused by the shingle eater.(those teeth can catch in the edge of the ply and rip a hole right in the wood)Now,lets consider whats gonna happen If you do a DIY tearoff.Since you already asked about tarps I figure you have considerred the worst.I wish I had a $1 bill for every time my phone has rung at 5:30 am on a monday morning with the panic stricken following message."my brother in law said we could save a lot of money by doing my own roof. we spent saturday and sunday tearing the old roof off and we have some of it tarpapered,but we have to go to work at our regular jobs today and it is supposed to rain this afternoon........So,even though I do almost nothing except roofing now,and the majority of my income is derived from nasty 2-3 layer tear-offs,I would still recommend the layover method over a one layer roof.In fact I will be doing this on my own house in the spring. It would have been done this fall but I was too busy tearing off customers roofs to work on my own house.The shingle you mentioned,or as george suggested an Elk product(my personal favorite)are IDEAL for a DIY layover situation.The best technique has already been described above and countless other places on this board.An exposed aluminum w valley works well,but can be difficult to handle and lay flat and smooth over woven valley by professionals,let alone by Diy types.I would suggest you use the closed cut or california valley detailed on the package.I would suggest either 90# roll roofing or a piece of modified bitumen as the UNEXPOSED flashing in your case. It will be more flexible and easier to work smooth in your application.Andrew,2 pointers1)don't waste time nailing cleats all over your roof for tearoff footholds.Just do it like we do. Climb to the top of your 12/12 and tear-off whatever you can reach from the ridge.Then reach down and jam a roof jack in the crack between 2 1x8's. When you step on it it will wedge itself in place and you can lower yourrself down and tear-off another area quickly. No nailing needed.1 guy can tear-off 5 sqx2 layers=10 sq in a couple hours on a 12/12.2)Don't ask questions,just nail down the bottom edge of the waste stack flashing and silicone the exposed nailheads.If you have seen as many wasps,birds,squirrels,etc. entering houses from that loose flashing detail,as I have, you would know why we nail it.Good Luck All,Stephen
*Stephen, thanks for all the roofing pointers, it was great to have a professional roofer respond. I got a lot of good pointers from your post. (Wasps .... hmmm .... hit home!)I have a question, too (always.) Do you consider the pitch of the roof when evaluating whether to do a layover or not? Is it possible to layover a 3 in 12 roof? 4 in 12? Thanks again!
*Ken,in my area(N.E. Ohio) a 4/12 layover is the easiest money I could ever dream of finding.I would do nothing but 4/12 layovers if I could sell enough of them.A 3/12 layover is another story.I don't consider 3/12 to be a suitable pitch for shingle application.Houses of this pitch are rare in my area and the few times I have been asked to bid on them I specified complete tear-off,icegaurd ENTIRE roof surface,install standard shingles using a 4"exposure and virtually no warranty. Needless to say,I didn't get any of those jobs(Much to my relief,actually)By the way,in a layover application it is often entirely possible to install all new flashing.We install new roof vents and waste stack flashings. Chimneys can be re-flashed with minimal fuss at this time,and of course valley flashing is no real problem to install in a layover.Installing new step flashing along a sidewall can be a pain in this application,but then isn't it always?Of course many houses have no roof/sidewall intersection to flashand so are a non-issue.In all honesty,the roof/sidewall application in a layover should at least get carefull consideration,meticulous fitting,and the highest quality caulk applicable.Now if only this mornings snow would melt off the roofs,I could finish my last jobs of the season and get on with my real winters work....swimming laps at the gym,and lounging in the sauna and steam roomsgood luck all,Stephen