These are topics that have been sked and answered 42 bijillion times if searching the forum.

 

Never liked overlays. It bakes your roof off and its hard to warranty when your already going over junk.

 

water and heat degrade asphalt shingles. water/moisture can get in between shingles in a variety of ways such as wind driven rain by the rakes or leaks.
by the way, have fun locating a leak when doing an over lay.
remember, another layer of asphalt will increase heat.

 

I gotta be the devil's advocate. People are always posting their reasons for why it is bad to do a re-cover yet no one ever includes proof that it's actually true. My question is is this a fact or a belief? Do you have proof of this "problem" or are you just going by what you were told?
I never really take a side on this issue the 42 bajillion times it has come up. I'm not from Missouri but I am a firm believer in "show me" before I make a judgement. I encourage other posters to do the same in anything like this or anything else pertaining to your trade. It will only make you that much more valuable.

Sooo, can anybody show me???

 

can I show you? How about the hundreds of roofs I have torn off that were 15 year old over lays? Proof enough not to do it. How about the fact that I live in the snow belt and those 20 year old roofs that people are overlaying have no ice shield and are not up to code on ventilation? Proof enough is my career experience that a lay over will last no where near as long as a tear off.


Why would anyone throw clean clothes over their dirty clothes? Too cheap and lazy to do it right and take a shower. Cheap being the key factor, people are cheap.

 

I have a lot of respect for Grumpy's point of view, and we always try to move our customer to a tear off to get the underlayment and ventilation to code. That being said . . .

A few years ago we received calls from a couple of customers who we had installed roofs for 25 years previous, installing new shingles over existing roof shingles. Same customers, same house. The shingles used were a 25 year GAF (if memory serves). We found the shingles to be in pretty good shape for their age. No excess loss of granules, not much curling . . .

The customers commented that in those 25 years they had no service issues, and that we were the contractor of choice to install a new roof.

In my professional experience, a second layer may not be a predictor of shorter shingle life.

In the agricultural community I was raised in, and which my grandfather and father provided roofing services to, it was common to install a 2nd and sometimes a 3rd roof. Of course, much of these type of applications were dairy barns and other agricultural structures, along with the occasional farm house (steep pitch, full 2" x 4"/6" rafters).

Call it backwoods or hack roofing, but fact of the matter is that our family enjoyed a reputation of installing trouble free roofs that went the distance, in a community that was pretty quick to identify substandard workmanship. That referral and word-of-mouth kept us busy was the proof of the quality of service offered.

As a licensed professional, I appreciate my heritage, but have moved to a business model that recognizes better value overall in stripping the roof and building a good roof system that meets code.

 

My main problem with layovers is that the existing flashings usually get re-used and often they won't last as long as the second layer.

It's not so much the process as it is the execution. When a layover is called for, money is the main driving force, and other shortcuts seem to get taken.

For example, if the step flashing is not woven into the top layer, water can enter between the layers.

Some roofs are better candidates for layovers than others. I'd have less hesitation doing a layover on a straight gable ranch with few penetrations than a victorian with lots of chimneys, valleys, and dormers.

 

The price is always the main factor, but the price difference between a properly installed lay over and re-roof is not as big as many contractors think.
If the bid on labor is $130.00 for a re-roof, the bid on a lay over would between $110.00/115.00.

It's the roofer/contractor who say's $55.00, $65.00 a square for a lay over that will do nothing but nail new shingles over old and those are the roofs that fail miserably.

 

I have to say it amazes me that you guys can get 25 years out a shingle roof. I had an home inspector call me the other day because he found a shingle roof that was about 18 years old which was installed after hurricane Andrew. The shingles had about 20% of the granules left on them and were cracking. They were so brittle they would fall apart in your hand. I mean I know our sun is brutal, but getting 25 years out of an overlay... Wow.

Here is what 18 years of sunshine does to a shingle down here:

JW
_________
JW Roofing - Miami Roofing

 

Here is what 18 years of sunshine does to a shingle down here:

JW
_________
JW Roofing - Miami Roofing

Where is "down here"? I imagine FL since I see Miami Roofing but I live in Globe AZ and our neighbor town is Miami. I don't see your location in your posts.

But here in AZ there is no way you get the years that the manufacturer suggests. Code here says you cannot put more than 3, yes 3, layers of shingles before you have to tear off. We would never "roof over" but I see it alot here from others.

 

Here goes guys.

I have personally owned two separate roofs that had 3 layovers each on them. the first was best I could tell about 40 years, so much for that shorter lifespan. The second was 30 years old as I remember when it was done, previous owner.

My theory is that both these roofs were over 12/12 pitch, in fact the second was gambrel with 24/12 pitch on the sides, is the steeper a roof the longer it lasts.....

I know I am listed as a framer, previous life was owner of a company specializing in roofing and siding... Believe me, I have done hundreds of houses, many layovers....

Seeyou is correct, if you install up to date flashing a layover can be a good choice...

 

I read this post, and it interested me. I will now offer my two cents...

I always thought it was best to just tear off and re-roof every time. The reasons I can think of are:

1. Just half a$$ to not tear off in my humble opinion.

2. Weight. Over the years a double and triple layer will make your whole roof sag. The sagging is not hard to spot. Think about people like me in the north who have a snow load to worry about. Then you add 3 layers of shingles? The trusses are not designed for that. A double or triple layer over 15 years or more will more than likely make the roof sag where I live.

3. Appearance. I can tell when a roof is an overlay. It looks like an overlay.

4. Leaks. If you ever had a leak, how would you locate it? It would be difficult with 2+ layers.

5. How do you even know the roof deck is in good condition? By walking on it to see if it feels strong? Hardly a good way of telling if everything is up to par. You are laying over, and don't know for sure how long it will last.

If you tear off, you can make sure the whole roof is in good condition, before you cover it up. However, I am sure there are experienced people who will get excellent results without tearing off first.

I just think the only reasons it is done are cost and ease of installation. Have you seen some of these church towers that are like 100/12 slope? Have fun tearing that roof off.

If it were my home, I would NEVER reshingle over existing. NEVER. I just think shingling over existing is always done because it's easier. Contractors will even recommend it sometimes, because they just want to bang it out, and get paid.

Labor, cost, and time aside: Which roof is a better finished product? Shingle over existing, or tear off and reroof? I think a tear off will be better and last longer where I live.:thumbsup:

 

My .02 is,
1. It's always best to tear the existing off instead of laying over them.

2. If the existing roof is being re-done because of aesthetics and is in fair condition, a lay over will work.

3. The procedure of a lay over is not what fails, the workmanship used to install the second layer is what fails.

I have numerous lay overs that I did in the 80's that are still intact today, one I drive by every time I go into Canfield, Ohio.
(which is where better then 80% of my yearly work is.)
It's a 100 plus square strip plaza that I laid over in 1987, which makes it 24 years old this summer, not a bad life span for OC Supreme and it's still holding up.
There's a second strip plaza just a few city blocks away done in the same time frame, maybe a little newer and it's holding up also.

The OC Supreme I laid over on my personal roof lasted 21 years, it still was not leaking when I tore both layers off last year and installed Tamko H.
I changed the color scheme of my home and the old Aspen Grey just stood out to much, so I re-roofed it even tho I could have gotten several more years out of it.

When I do a layover you don't see that from the ground.
A poor/inexperienced sales person/estimator would even miss it from the roof.

 

The procedure of a lay over is not what fails, the workmanship used to install the second layer is what fails.

That is a great way of summing it up. Agreed.

 

I always ask if they think it's going to be cheaper to tear them off and get rid of that second layer in 25-30 years.

If'n it was my money I would tear them off.