Need some roofing advise, please.
I’m going to re-roof my house, which has an average pitch to it. It currently has a three tab, Composition Roof, and only one layer. The new roof will be Composition also, but probably a different design, something thats not quite as boreing as three tab. Here is the question….Do I need to, or should I tear of the old roof, or can I lay the new one over the top? I know it’s sometimes done, but is it advisable?
Any and all input would be welcome.
Thanks,
Mike
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Replies
First - there is no average pitch. Certain slopes are more common in certain areas and not in others. Since youhae shingles performing nowt though, it seems that you must have at least 3 or 4 / 12
Most manufacturers will not warrantee the products over other roof materials. There are various reasons, but you should know this.
Additionally, it can be trickier to apply shingles over old.
And - you should not do ti if the old roof has curling shingles. The old ones should be still solid and laying flat to the deck.
In short, It canbe done, but there are risks and it can be a wast e of time if the old is all curling up
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I like to remove old shingles to see what condition the roof sheathing is in. My wife had new shingles put on her house before we were married and although they stripped off the old shingles, they left rotten sheathing at the eves, so the gutters on straps they nailed to this punky wood are all coming loose with no way to nail them firmly now.
Also, if your roof is very old, they probably did not put bituthene ("Iceguard") at the edges. I had a customer who was complaining about water dripping through his soffits. I went out and saw that he had shingles over an old layer of shingles and no bituthene. I told him he had ice dams and if he wanted to get rid of them, he should reshingle. Since roof was less than ten years old he wasn't ready to spend money on re-roofing, so I told him next best thing would be electric tapes to melt the ice.
Incidentally, on that house they didn't bother with drip edge, so the water ran back up the underside of the shingles at the eves and then down the fascia and between it and the gutters. I shoved drip edge under the top layer of shingles and lo and behold, water actually went into the gutters. He said he'd never seen so much water come out of the downspout before. He had had water coming through basement wasll before that too, so this really helped.
I agree that you should remove the old shingles. If nothing, it will let you evaluate the current condition of your roof and replace any rotten sheathing. "Ice and water shield", "iceguard" or any other rubber-like, impervious membrane needs to be laid down at the eaves, rakes, ridge and other locations. This is your last line of defense against water getting into your attic and can, depending on where you live, help in the fight against ice damns. The real culprit in ice damning is the freeze-thaw cycle of snow. Hot air is allowed to escape from the attic (usually at the soffitt where ventilation does not occur because insulation runs to the underside of the roof deck) melts the snow and once this water runs onto the overhang where it is cold, freezes again. Ice damns push the water back up under the shingles and this is where the 3 feet (minimum) of membrane comes into play.
Ice and water sshield wil do nothing to prevent ice daming. It will simply prevent the water that backs up behind an ice dam from leaking in.
Preventing the daming involves proer ventilation and insulation of the assembly
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You are right. Ice Gaurd doesn't prevent ice dams, but it is nice to have it if you get an ice dam. As you said, the solution is proper ventilation and insulation to keep the roof cool.
I agree with "rip off" the old shingles. I have seen way too many reroofs over existing shingles that fail prematurely. In Northern Michigan, a typical 25 year roof, placed over existing shingles will typically last 6-10 years.
The underlying shingles will continue to dry out and/or curl and cause the pattern to transfer to the new shingles, sometimes lifing the new ones up and making them susceptible to blow off.
Tear off, survey the decking, place your snow and ice guard and vent!!!!!!!!
Since it is the UV rays of the sun drying out the shingles, I fail to see how it is possible for them to continue curling. If lift off occours, it is more likely that the second layer wer bnot six nailed or that the nails were not long enough to penetrate the deck sheathing.
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Mikie,
Just as all the others have said...it is best to do a complete tear-off. All the reasons previously given are very real and valid...and if for no other reason, a new roof will always look better than one that was roofed over...period. Since you don't like the look of 3- tab, go with a 30 year architectural ( dimensional) style, they look very nice.
Davo
Hi Mikie,
I'll throw in my 2 cents worth . As a former roofer, now general contractor, I used to always be a proponent of doing tear offs. A few conversations with roofing inspectors have changed my mind somewhat on this.
Tear-offs are more expensive and sometimes un-necessary (Please see CASMA Technical bulletin #6). You have dumping fee's, aditional labour and depending on the age of the house you may have to sheath over top of the existing sheating if it is planking. If the existing roof is in good condition ie. no curling, no leaks (check in the attic and look for water stains), not too brittle, then you should be able shingle over top of the old. Remember that your nails should be sufficiently long enough to penetrate plywood decking.
I like doing tear-offs when there is any question as to the stablity of the roof decking and/or the existing shingles are curling. The extra time and cost is well worth the peace of mind. It is easier to install new shingles over sheathing rather than existing shingles.
In either case, the look of the job depends upon the time you take to properly prepare the decking or existing shingles and the time taken to lay out the shingles using vertical and horizontal chalklines. The warranty shouldn't be affected if installed properly. Shingles installed on wood planks (1x12's etc) are usually warranteed for half the years ie. 25 year shingles are only warranteed for 12.5.
Check out the CASMA or the ARMA websites for some more info.
Budman
Mikie,
I endorse all the previous comments about stripping the existing roofing instead of going over it. Another reason to strip it is resale value. Most building codes (BOCA) allow a maximum of two layers of roofing. Even if you intend to live there forever you never know. When selling the house having the one layer will look better and if buyers think they can save money by adding the second layer when it's their turn to roof they will justify the savings in their mind. (But I hope they choose to do the "right" thing too.)
P.S. I bought a 100 +/- year old 3-family slum-lord tenement to fix and live in that never had a layer removed! I estimated the newest one to be 25+ years old (later confirmed by several roofing contractors) and dead! There were 4 layers of roofing including the original cedar roofing! My bid deducted the anticipated (expensive) added cost of properly installed roofing. So...STRIP IT!