Architectural Shingle Re-Roofs & Tear-Offs
Full tear-off to the deck, every sheet inspected, then synthetic underlayment and architectural shingles. We do not roof over failing material to save a day.
Tear-off versus roofing over
California allows a maximum of two layers of roofing on a structure. That means you can legally shingle over one existing layer — and plenty of contractors will, because it removes a day of labour and a dumpster from the bid.
We tear off. The reason is simple: you cannot inspect a deck you cannot see. Rot, delamination, failed sheathing nails and previous leak damage all live under the old shingles. Covering them means the new roof is fastened into compromised wood, and the first real problem shows up as a warranty argument rather than a repair. A layover also traps heat, which in Valley summers shortens the life of the new shingles measurably.
The assembly, in order
- Deck — every sheet walked and probed; soft or delaminated sheathing is replaced, not shimmed
- Synthetic underlayment — tear-resistant, across the whole deck, not just the eaves
- Self-adhering membrane — at valleys, eaves, rakes and every penetration
- Starter course — a real sealed starter strip at eaves and rakes
- Architectural shingles — laminated, nailed inside the manufacturer nailing zone
- Ridge cap and ventilation — ridge vent sized to match the intake at the eaves
About that membrane at the eaves
Most roofing literature calls this “ice and water shield” and explains it in terms of ice dams. We do not get ice dams here. Stanislaus County almost never sustains the freeze required. The reason we run self-adhering membrane at eaves, valleys and penetrations in the Valley is wind-driven rain — during an atmospheric river, water moves sideways and uphill under shingles, and the membrane is what stops it reaching the deck.
If a contractor tells you that you do not need it because it does not freeze here, they have learned the rule and missed the reason.
Nailing
Manufacturers specify four nails per shingle in standard conditions and six in high-wind zones. On exposed Valley elevations — west-side properties, anything on an open lot with no windbreak — we use six. Nails are the cheapest component on the roof, and wind uplift starts at the edge and works inward.
Ventilation matters more than the shingle
The single most under-specified part of a Valley roof is attic airflow. Code asks for one square foot of net free ventilating area per 150 square feet of attic floor, or 1:300 when the intake and exhaust are properly balanced between the eaves and the ridge.
“Balanced” is the operative word. Ridge vent with insufficient soffit intake does not draw — it can actually pull conditioned air out of the house. Get the ratio right and an August attic runs meaningfully cooler, which slows the aging of the shingles from underneath and takes load off the air conditioner. This does more for the life of a Valley roof than upgrading the shingle line.
What it costs
Architectural asphalt shingles with a full tear-off run $6.50 to $9.00 per square foot installed in Stanislaus County — roughly $16,000 to $23,000 on a typical 2,400 square foot roof. Steeper pitch, two-storey access, multiple existing layers and deck replacement all move that number. Concrete and clay tile run considerably higher and need a structure rated for the weight.
Architectural asphalt shingles carry 30 to 50 year ratings, and in Stanislaus County the realistic service life is 20 to 30 years. Valley heat and UV are the limiting factors, not weather damage. Attic ventilation is the biggest variable within your control: a poorly ventilated attic cooks the shingles from underneath and can cut a decade off that life.
Legally yes if there is only one existing layer, but we do not recommend it and do not offer it as a default. You cannot inspect a deck you cannot see, and a layover traps heat that shortens the life of the new shingles. The saving is one day of labour and a dumpster; the cost is an uninspected structure under a new roof.
A typical single-storey Modesto home with one layer to remove is one to three days. Two-storey, steep pitch, multiple existing layers or significant deck replacement pushes it to three to five. We never leave decking open overnight — if a section cannot be dried in before the crew leaves, we do not open it that day.
Lighter colours reflect more solar energy and run cooler, which helps both the attic and the shingle's own service life. The difference is real but modest — a well-ventilated attic under a dark roof will outperform a poorly ventilated one under a light roof. Choose the colour you want the house to have, then spend the attention on ventilation.
Tell us about the roof.
Free inspection, free written estimate, no pressure. If it is an active leak, please call — the phone is faster than any form.