2nd layer of shingles or tear-off/re-roof

[ArkTinkerer]

Title pretty much says it all. Roof is getting old but no major issues. Want to add a ridge vent if that matters. Debating just applying another set of shingles as opposed to doing a full tear off. I've seen houses with three layers and don't think I'd go that far but two layers doesn't seem to be a problem. Anyone do a second layer and run into problems? Does the second layer add insulation worth mentioning?

ArkTinkerer

[little jimmy]

I have always taken the old ones off. It is just my prefference. Lots of people do two layers and dont have a problem. Heck one rental had wood and then three layers of asphalt on it. As for insulation, I would say that there cant be much if any value to think about. If the old ones are rolling up then it will be hard to keep the new laying flat. Good luck either way.

[Toolman12]

I have put many shingle roofs down before with my father and IMHO if the existing shingles are not rolled up or missing then go ahead and go over top. if they are rolled then just cut the tabs off it's a lot less waste to have to haul away. Use longer nails and wait for a few of good hot days to put them on so they seal fast and strong. the advantage of complete tear off is seeing if there is any damage to the roof itself a company will always want to do this because it adds to there bottom line. So if no leaks and no rot then save a lot of time, money and mess and just go over top IMHO

[Norcal]

Remove the old ones, overlay roofs are a poor practice. Stripping the roof also makes possible for the sheathing to be repaired if needed.

[Big Poppa]

dont do a second layer of shingles unless that is all you can afford.... always better to strip it down to the boards....

[79firebird]

I my self perfer to tare off and not do a second layer depending on how the roof truss's are due to all that added weight.

[NUTTSGT]

I've often heard that if the current shingles are in decent shape, you can put a second layer on them. It makes me wonder to myself, if the shingles are in that good of shape, why are you putting new ones on?

Just my 2¢, I'd tear off the old.

[bob15]

Strip it. It's a no brainer.

Not sure where you live, but consider the weight of a second coarse of shingles, plus potential snow loads. Sure it might seem petty, but if you're in the North and get a record year of snow, collapses can and will happen. Your house will be happy without the extra weight.

Plus, by stripping it, you can lay down water & ice which will help prevent water damage should you have ice dams on the gutters. Also gives you a good chance to see how your plywood or tongue and groove roof boards are doing.


bob

[signcrafter]

Tear it off, no question here.

You will NEVER get as good of a seal going over the top of another layer. Roofing materials are like a puzzle with the ice dam, tar paper, valleys, flashing, etc. Tear it off so you can see any issues there may be that you can't see right now. Then start fresh. You will have piece of mind that you did the job right. With the wood in good shape start putting the pieces together. The roof will seal better and lay flatter. Think about it this way, when you put new shingles down you put them down on a flat wood roof with flat tar paper/ice dam on it. If you put a second roof on you are putting it on shingles that aren't really flat, they have spaces and also years of deterioration from the weather, even if they look in decent shape.

I've helped a few friends in the past do a second layer but I would never do it on my own home. The little bit of work it takes and cost to haul away it's just not worth it.

Now the one time that I might consider it is if I found cedar shakes under the original layer! I've done a few roofs that had two layers of shingles and cedar shakes and those suck. Take forever to tear off and then have to re sheet the roof. Not fun and in that instance I might consider just putting a second layer on!

[jeep450]

As long as you have regular 3 tab shingles. If you have architectural shingles you have to tear off because the weight will be too much.

[Falcon67]

Well - if you have, say you have 20 square up there of regular 3 tab. That's about right for a 1600~1700 box sq/ft with a 6/12 pitch. You'd double the weight from around 4500 lbs of shingles to 9000 lbs of shingles. Then next time, you HAVE to take them off. Think about the amount of extra work, the size of the dumpster to get rid of them, etc.

[nkachur]

This is an issue you will never have an agreement on. In my opinion strip the roof, it will allow:
- you to repair any sheathing damage
- reduce the weight load on the truss / rafter system
- get a better lay

the only advantages to putting a second layer on are:
- less work
- no disposal fees

If you can afford to upgrade metal is a better product than asphalt for your replacement.

Just my 2 cents.

[Gary S]

I've done it both ways. The second layer adds weight, but if your roof is structurally sound, it isn't an issue. I live where we get very heavy loads of snow some winters, and have never seen a residential wood frame house fail to handle the snow load with two layers of shingles. I see failures on commercial buildings designed by architects and engineers, but not on wood frame houses.

So, it is your choice.

[joshmodelskidoo]

if theres no damage and the shingles are still ok, the drip edge is good and no leaks i would just slap on another layer. i have herd of people even doing a 3rd layer buy i wouldn do that. depending on how steep your roof is you might want to put on some ice berior also. i have to redo my roof with a single layer on a double wide with rotted wood under the shingles on the overhang so its all getting torn off and iinsulation while im at it. you can always call up some roofers and see what there opinion would be

[Stuart in MN]

I think most building codes will allow two layers of shingles, and if the first layer and roof deck are still in good shape you can probably get away with it, but I think you'll be better off stripping the old shingles - that way you can be sure there are no hidden problems.

[Boomer343]

Check the warranty on your new shingles....most require certain underlays and if installed over existing shingles the warranty may be void.

Personally I'd strip and cover the decking with the ice shield....especially if skylights or valleys are involved.

[Rod N]

I left mine on and did a metal roof on top for $2 sq/ft.

[coolreed]

Take the old tiles off.

[dirttracker18]

Originally Posted by NUTTSGT

I've often heard that if the current shingles are in decent shape, you can put a second layer on them. It makes me wonder to myself, if the shingles are in that good of shape, why are you putting new ones on?

Just my 2¢, I'd tear off the old.

This ^^^^^^

Lots of guys go two layers, good guys never do. It is poor practise to layer them. Do it right the first time.

I will also second metal roofing. Easier to instal, lifetime warranty, and looks and performs great.

[SuitorsGarage]

Do it right the first time and strip the old shingles off.
Only a fly by night or hack roofer would do a second layer in my opinion. I worked for a commercial roofing company for 11 years. We didn't do new construction, only re-roofs. We did not specialize in shingles but did plenty of them. Our idea of a shingle job was 100 or so condo/town homes in one shot remove, repair, replace. Never would we do an on over shingle job.
Now I am a self employed contractor. I will do roofs. I always insist on tearing off the old. I don't do it to get the price of the job higher. I do it for the quality of the work. I've ripped my share of roofs with shingles being the easiest to rip and really I could care less if I ever rip another one. Putting a second layer on is taking the easy way out. I won't do it that way if I do a roof. When I'm done with a roof I give a 2yr warranty myself. How do you know what the condition of the deck really is unless you see it for yourself.

Above all think safety! I know it is not an easy thing to do at home sometimes but you can get just as hurt on your own roof as roofing for a living.