Take the old off or leave it on ,that's my question
 

I have roofed a few houses in my day ..and all of them but the last one ,,, I used a air nailer
One thing I never considered doing is putting roofing over the top of roofing .
So, beings my roof is close to 20 years old and still laying flat and not curled up or any breaking tabs off
What is your advice on leaving the old on and roofing over it?

My reason for leaving the old on is for two reasons . less cost to install a new roof and more insulation

Re: Take the old off or leave it on ,that's my question
 

I have not done a lot, but do it right. Clean off the old , then add the new. Guy I worked for used that quote a lot. 1 you can see what is beneath for a foundation, 2 you know it will lie correctly.

Re: Take the old off or leave it on ,that's my question
 

Im not a roofer, but with a shake roof, I would replace than cover. Asphalt shingles you can get away with that. They never really curl up. I would worry the old shakes underneath may cause issues with the new ones.

I totally get your point to cover them with new.

Re: Take the old off or leave it on ,that's my question
 

Sorry ,, I deleted the part about me installing a shake roof ,,I didnt mean to cover a shake roof with another shake roof or asphalt .. I am only considering covering a Asphalt roof with another Asphalt roof

Re: Take the old off or leave it on ,that's my question
 

No worries. I have done this to my 10x12 shed when I built my garage and re-roofed the house. That was in 2005. No issues at all. There was nothing wrong with the shed roof, but I wanted them all to look the same.

My original roof is 3 tab shingles and I covered it with dimensional shingles which are sorta twice as thick. Appearance wise it looks a little thick on the edges, but not that noticeable. I can snap some pics of you like.

Disclaimer: Im not a roofer. :) This worked for me. Where you live in Idaho and probably get snow in the winter, you may want to consult a roofer or engineer in the area about the additional load on the trusses/walls/foundations etc.

Re: Take the old off or leave it on ,that's my question
 

check your building code. In most places its you can do two layers so you can leave it there if you want. I perfer to take it off and relay ice shield and paper as well as search out any dry rot or week wood underneath

Re: Take the old off or leave it on ,that's my question
 

going over 1 layer is fine...if their not laminate shingles.
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they are double thick and can cause the new ones to sit crappy, not lay flat and seal properly..
if you have square butt or old t-lock shingles, not a prob. in fact t-locks were made to go over top of old shingles, but their pretty much out of production now.
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of course it's always nice to remove the old ones, but sometimes there just isn't enough money (besides labor, disposing of old shingles is not cheap, there petro based and their heavy) or whatever other reason. if you go over top, go up in your attic and check the deck, any probs will be visible from below.
also trim your eave shingles (gutter line) back flush with the deck and your rake ends flush too. install your new starter row out a couple inches into the gutter just like before, and run a row of shingles up your rakes hung over an inch. won't get that big bulky ugly look and gives a nice straight edge to cut the shingles to.
synthetic underlay is also way superior and better lasting than using felt (tar paper)
when going over top, ventilation is now critical so your roof won't sweat. don't know what the specs are where you live, but a good rule of thumb is one AF50 roof vent for every 600 sq ft of living space
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this is my 40th yr slinging tar and banging shingles, any questions just ask

if you have trusses, no worries about weight. roof trusses are engineered usually for a min. 4000 lb snow load, you will only be adding a couple hundred lbs per square. we actually did a house 'bout 10 yrs ago that had SIX layers, swear to god that house popped up 2 inches once they were all off

Re: Take the old off or leave it on ,that's my question
 

No reason to leave the old ones on. Its just extra weight. Pull them off, make sure the roof deck is good with no issues and make sure you have ice and water protection. A couple of shingle shovels and a couple of young bucks can have the roof cleaned off in no time.

Re: Take the old off or leave it on ,that's my question
 

I roofed for 30 yrs ,how old are u ,how loong are u there for, your aloud to go over original shingles once ,if u plan being there strip it know sense spending money on it and then leaving

Re: Take the old off or leave it on ,that's my question
 

My contractor put on ventilated cap shingles, so no holes in the roof* except for the plumbing vent. It did have one of those wind turbine things.

* my chimney is at the eave so just a square notch

Re: Take the old off or leave it on ,that's my question
 

Whatever you decide remember...."It only has to outlast you and the wife"... All kidding aside there is nothing wrong with putting new asphalt shingles over 1 previous layer.

Re: Take the old off or leave it on ,that's my question
 

Do you think it safe enough from wind if you put Architectural shingles on top of a old roof of Architectural shingles?

Re: Take the old off or leave it on ,that's my question
 

I'm no roofer but I own a house in Fairfield that I rent to x in-laws. I went replace the roof and found four layers, yes four. I stripped it and redid it. After removing all that weight most walls cracked and the doors didn't close. It turned into quite a job, I guess I should have looked closer when I bought it. There were no permits pulled for the three additional layers.. Live and learn, that was definitely a feathers day. LOL..

Re: Take the old off or leave it on ,that's my question
 

depends...
for wind protection the shingles need to seal to each other to prevent wind lift.
as stated it's not a very smooth surface (double laminated) but if you live in a pretty warm climate, they would get hot and soft enough to seal despite roughness.
in 60-65 degree weather it will take about a month for them to seal. in northern climes it can take longer meaning more chance for the wind to get under them. as we install them in the winter in freezing or near freezing, we put a tab of fiber cement under the shingles to hold them down until warm weather can seal them up.
would also use an 1 1/2" roofing nails too, anything shorter thru 2 layers of laminate opens you up to the wind again.
would also try to stagger the new rows from the old, wouldn't try line them up

Re: Take the old off or leave it on ,that's my question
 

yep, another good way to vent your roof.
there is actually quite a few different ways to vent roofs now a days. all depends on what you like and what your budget is.
those "wind turbine things" make me money, don't take much to knock them out of whack and start squeaking....
having proper ventilation is the key to roof longevity and less probs.
you would not belive how many leak calls i've been on that turn out to be condensation problems- 99% of the time crappy or no ventilation..

Re: Take the old off or leave it on ,that's my question
 

The new roof may not be too "Architectural" if it's not laying on a somewhat flat surface would be my thought.

Re: Take the old off or leave it on ,that's my question
 

I wouldn't lay a new roof over an architectural/laminate shingle roof and expect good results. As a contractor, jobs I get where new roof goes on old, the old always comes off. If for no other reason, I want to see the sheathing/framing beneath the shingles to assure there has been no water damage. I get where you are at with this, though, and this is your own home so different from hiring on. Tear-off (for me) is the larger part of the labor, plus there is disposal. If you have tab shingles then go for it.

Re: Take the old off or leave it on ,that's my question
 

back when Dad was in the fire dept, they put out their share of house fires... he said the hardest to put out was where people put lathes and metal roof over shingles...with the lathing on the shingles it allowed air to get under the tin and the shingles would burn like a furnace...
i know your not doing metal but food for thought..

Re: Take the old off or leave it on ,that's my question
 

Hah! I put on a metal roof like that once. It wasn't over old shingles, it was a new log cabin 2x2 plus styrofoam plus metal over 2x6 t&g on 6x6 rafters. I told the owner who I was helping day labor that we needed to put a couple long nails through the 2x2 and t&g into each rafter, but he was afraid we would miss a 6" wide beam and stick a nail through his ceiling into the open beam cabin. So we just used 10d nails into the t&g. :rolleyes:

That winter there was a big wind and the whole damn thing, metal, styrofoam, and 2x2's, flew off into the national forest! :lol:

Re: Take the old off or leave it on ,that's my question
 

As always,,,good information on here about what in the long run would be best.. ,,,,,,,,,,,,,,I will have the old taken off and new put on,, I come from old school and never did believe in using staples to fasten the asphalt shingles down , so I will hire a roofer who uses tacks.. other than that ,,you all have convinced me that it is best tear it off and then see if any of the roof needs replaced ,, thanks guys

There is one more question I have always wondered about,, when you put a new roof on with the same type and size roofing ,, wouldn't the new roof nailing hit in the same area as the old roof ,,therefore many nails in the old nail holes ? just had to ask,:)

Re: Take the old off or leave it on ,that's my question
 

You'd have to be pretty lucky to hit many of the old nail holes. I wouldn't let that be a worry.

And with a proper roofing nail gun it's just as fast as with staples.

Re: Take the old off or leave it on ,that's my question
 

Thought I would add a short story to my roofing of my house I owned back in Oregon a I know some of you have done this yourselves .


After doing my last remodel on my house in the 70ies of adding onto the end and back side of my house ,,, I put on heavy shakes which was popular back then,

Then in 2005 with finding leaks in the roof around my sky lights I took all the 32 square of shakes off and went to asphalt shingles ,, I tore off all the shakes and my dad wheeled them up back and stacked them up.. Lots of wood stove kindling. (also had lots and lots of 1980 Mt St, Helens Eruption Ash in the shakes that was helping moss to grow..

I bought a Bostitch air gun tack nailer with the round rolls of tacks and put 4 tacks in per shingle ,,not 3 tacks per shingle like a lot of guys were doing back them who were in the business of roofing .


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Re: Take the old off or leave it on ,that's my question
 

actually there is quite a bit of truth to that. many older customers who are either on a fixed income, want to spend their money on grandkids, want to travel, or knew their time was coming and could just not see going all out for something when short of time...

that's all todays shakes are good for-kindling. look in the back of my truck, brand new re-saw shakes going up in flames keeping me warm. we have tons of these at our shop. shakes now a days are nothing like what we got back in the day. wood quality is not there, hand-splits or re-saws. i've pulled off 5-10 yr old shake roofs that are just wasted, we're into second and third growth trees now. if you can find some good old growth, them blocks are worth a pretty penny. i've been on 100 yr old barns with 40-50 yr old old growth shake roofs on them, you will find the shakes are like a foot and a half wide and when you pull them up, flip them over and they look just like new still.
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nice job on the roof!
last house i did was my own 5 yrs ago. the place i work we do commercial, industrial and government exclusively, malls, apartments, schools, hi rises, factory's etc. average house is 20-30 squares, we do 4-5-600 sq roofs and bigger.
never really thought to take a before of mine. and ya, there is sq butts (3 tabs) under them grey t-locks. previous owner obviously didn't want to spend so they went over top. got 20 trouble free yrs, and they weren't leaking, but they were gettin' a little thin and wore out, so figured better do it before it starts to leak. the only drawback of going over top is the cost down the road when re-roof time comes up again. now you have twice the disposal and labor costs. my labor was free, but i did pay more for getting rid of 2 old roofs...got a saying in roofing, "the roof is only about 5% of the cost of your house, but it covers 100% of your investment"
before and after
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this is more the scale i do now, big roofs, where quality is important. another saying we got in the roofing trade is "do it right, water has very narrow shoulders" :lol:
and we been using 5 nails on laminates since the '80's, up to 9 nails on Presidential shake/shingles-all comes back to quality and what the customer can afford...a re-roof is not cheap...
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Re: Take the old off or leave it on ,that's my question
 

diesel dawg

I bought my shakes back when we still had old growth coming out of our woods .. lots of shakes went to California back then and then later they outlawed them I think due to such a fire hazard.. My back would of never taken what you are roofing .. In fact I went to metal roofing with all my jobs back in the 80ies and that was only about 10-12 roofs .

Re: Take the old off or leave it on ,that's my question
 

A neighborhood in Colorado Springs that was subdivided back in the 1970s required shake roofs on all the houses.

In 2012 the Waldo Canyon Fire burned down most of that neighborhood ("mountain shadows" or something like that).

That same day a lightning strike from several days before about three miles from our house blew up and destroyed 70+ houses and uncounted sheds and vehicles.