Bella Construction recommends a full tear off on nearly every roof, and the reason is simple: a roof over saves $1,000 to $2,500 up front on a typical Pittsburgh area house and costs you 5 to 10 years of roof life, most of your manufacturer warranty, and any chance of finding rotted decking before it fails. Pennsylvania’s residential code allows a second layer of asphalt shingles only when the existing roof is a single layer, dry, and flat, and never allows a third, so most homes in Westmoreland County built before 1995 are not even eligible.
We have torn off thousands of roofs since 1995, including two, three, and once four layers off homes in Irwin, Greensburg, and the South Hills. Here is what we have learned, and the few narrow cases where a roof over can make sense.
What is the difference between a tear off and a roof over?
A tear off means stripping the old shingles, underlayment, and flashing down to bare decking, repairing that decking, then installing a complete new system: ice and water shield, synthetic underlayment, drip edge, starter, shingles, ridge cap, and new flashing and vents.
A roof over, also called a layover, means nailing new shingles directly on top of the old ones. No decking inspection, no new underlayment, no new ice and water shield at the eaves. Flashing is usually reused.
Does Pennsylvania building code allow two layers of shingles?
Pennsylvania’s Uniform Construction Code follows the International Residential Code, and the rule is clear. Two layers is the maximum. If your roof already has two layers, the code requires a full tear off. The code also prohibits a roof over when the existing roof is water soaked, deteriorated, or sits over wood shake or slate. Municipalities around Pittsburgh enforce this through the permit, and North Huntingdon, Murrysville, and Monroeville will ask how many layers exist. Answer honestly, because an inspector can see layers at the drip edge from the ground.
Why does the weight of a second layer matter?
A square of architectural shingles weighs 250 to 400 pounds, so a second layer on a 25 square roof adds 6,000 to 10,000 pounds. Modern framing can generally carry that. Many older homes in Norwin and across Westmoreland County were framed with 2 by 6 rafters on 24 inch centers and thin sheathing, built for one roof, and they already carry a Western Pennsylvania snow load every winter. Adding a second layer on top of that is asking a lot of 60 year old lumber.
Does a roof over shorten the life of the new shingles?
Yes, and by more than most people expect. A second layer sits on the bumps and edges of the old one, so it never seals perfectly and never lies flat, and wind driven snow finds those gaps. Heat is the bigger problem. The old layer traps heat under the new one, and asphalt ages by heat, so a roof over bakes the oils out of the new shingle faster through every Pittsburgh summer. In our Westmoreland County jobs since 1995, roof overs we have replaced averaged 12 to 15 years of service, while single layer tear offs with the same shingle average 22 to 28. That is the whole savings gone, and then some, in lost life.
What hidden damage does a tear off find that a roof over hides?
This is the part that worries us most. When we tear off a roof in this climate, we find soft or rotted decking on roughly one in three homes, usually around chimneys, in valleys, at the eaves where ice dams sit, and around old bathroom vents. You cannot see any of that from the top of the old shingles. A roof over nails new shingles into that rot. The nails do not hold, the rot keeps spreading, and you find out when a foot goes through the deck or a stain appears on the bedroom ceiling. A tear off replaces those sheets for $75 to $150 each while the deck is open. Our roof replacement cost guide explains how we price decking so there are no surprises.
Will a roof over void my Owens Corning warranty?
It will limit it badly. Owens Corning’s standard limited warranty allows shingles over one existing layer, but the enhanced warranties that matter, the Preferred and Platinum Protection coverage that includes labor and workmanship, require a complete tear off and a full Owens Corning system installed by a certified contractor. Details are on the Owens Corning warranty page.
As a Platinum Preferred Contractor, we can only register the Platinum Protection warranty on a full tear off. It covers the shingles for their lifetime and our labor for 25 years, and it transfers once to a new owner. A roof over gets the basic material warranty only, with no labor coverage. We explain what the tiers mean in our post on what Owens Corning Platinum actually covers.
Does a second layer of shingles hurt resale value?
It does, and the home inspector brings it up. Every buyer’s inspection report around Pittsburgh notes the number of layers. Two layers means the next roof is a mandatory tear off with double disposal, and a sharp buyer’s agent will ask for a $3,000 to $6,000 credit to cover it. A single layer roof with a transferable Platinum warranty is a selling point. A layover is a negotiation point.
Tear off vs roof over: a side by side comparison
| Factor | Full tear off | Roof over |
|---|---|---|
| Cost on a 25 square Pittsburgh home | $12,000 to $20,000 | $10,000 to $17,500 |
| Savings | None | $1,000 to $2,500, mostly labor and disposal |
| Expected lifespan | 22 to 28 years locally | 12 to 15 years locally |
| Decking inspected and repaired | Yes | No |
| New ice and water shield and underlayment | Yes | No |
| New flashing | Yes | Usually reused |
| Owens Corning warranty | Full Platinum Protection with labor coverage | Basic material warranty only |
| Allowed by PA code | Always | Only over a single flat dry layer |
| Effect on resale | Positive, transferable warranty | Negative, buyer credits common |
| Next roof cost | Standard tear off | Two layer tear off, higher disposal |
Last updated September 2026. Prices are for architectural asphalt shingles on a typical two story home in the greater Pittsburgh area. Steep pitches, multiple layers, decking replacement, and chimney or skylight work move the number.
When is a roof over acceptable?
A few narrow cases. A detached garage or shed with a single flat layer and no leaks is the most common. A house that will be demolished or rebuilt within ten years is another. Occasionally a homeowner with a 10 year old single layer roof that has a cosmetic problem, like a bad batch of shingles losing granules, will choose a roof over knowing exactly what they are trading away. In every case the existing layer must be single, dry, flat, and free of rot at the eaves, and we put in writing which warranty they are giving up.
Frequently Asked Questions
Is it cheaper to put a new roof over the old one?
Yes, by about $1,000 to $2,500 on an average Pittsburgh area house, because you skip the tear off labor and the dumpster. That savings usually disappears in lost roof life, a weaker warranty, and double disposal on the next roof.
How many layers of shingles are allowed in Pennsylvania?
Two. Pennsylvania follows the International Residential Code, which allows one new layer over one existing layer of asphalt if the old roof is dry, flat, and not over wood shake or slate. A roof with two layers must be torn off before new shingles go on.
How long does a roof over last compared to a tear off?
In our experience across Westmoreland and Allegheny County, a roof over lasts 12 to 15 years and a proper tear off with the same shingle lasts 22 to 28. The old layer traps heat and keeps the new shingles from sealing flat. See our post on how long a roof lasts for more on what shortens roof life here.
Can I get an Owens Corning warranty on a roof over?
Only the basic material warranty. The Preferred and Platinum Protection warranties that cover labor and workmanship require a full tear off and a complete Owens Corning roofing system installed by a certified contractor. A Platinum Preferred Contractor like Bella cannot register the Platinum warranty on a layover.
If your roof is due and someone has quoted you a layover, let us take a look before you sign. We inspect for free across Irwin, North Huntingdon, Murrysville, Greensburg, and the greater Pittsburgh area, and if a tear off is the right call, financing can close the gap between the two prices. Fall schedules fill by October, so call (724) 515 5163 or visit our roofing services page to get on the calendar before the first hard freeze.