Roofing H USA works on roofs across Los Angeles, and the codes the City enforces answer this question with a short list: some roofs may take a new layer, and others must be stripped down to the deck first.
Laying new roofing over existing roofing is what the codes call a roof recover. It is allowed in some cases and ruled out in others, and the City’s building code even sets which new materials may go over which old ones.
Settle this before you compare a recover quote with a tear-off quote. The sections below cover the limits, the material table, the cool roof rule and what the quote should show.
When does the Los Angeles code rule out a roof recover?
Los Angeles does not take the state’s roof recover wording as written. It writes its own section into the Los Angeles Building Code, and that text lists three conditions under which new roofing may not go over the old covering.
The first is a roof that is water-soaked, or so deteriorated that it no longer works as a base for more roofing. Next comes an existing covering of slate, clay, cement or asbestos-cement tile.
The third is a roof that already has two or more applications of any type of roof covering. A roof that was recovered once has reached that point, because the original roofing and the overlay count as two.
Detached houses and duplexes follow the City’s residential code instead, which builds on the state residential code. Its reroofing section lists the same three conditions, so on a tile roof the tiles come off before anything new goes on.
When can the old roofing stay in place?
Both codes start from the same basic case: a recover is allowed when the new covering goes on following the manufacturer’s approved instructions, so those instructions end up deciding the details of the job.
The Los Angeles Building Code then names two systems. A complete and separate roofing system, such as standing-seam metal panels that carry the roof loads straight to the building’s structure without leaning on the old roof, does not require removing the existing covering.
A new protective coating over an existing spray polyurethane foam roof is also allowed without a tear-off. That case concerns flat roofs on buildings such as apartments, offices and the other commercial roofs we work on.
All of these still sit under the three exclusions above. A foam roof that is water-soaked, for example, is not an acceptable base for a coating or for anything else.
Which new materials can go over which old roofs?
The Los Angeles Building Code adds a table of allowable reroofs over existing roofing, and it narrows the choices further. An existing tile roof takes no overlay of any kind, and an existing metal roof takes only new metal.
Over asphalt shingles, the table allows new asphalt shingles, metal and modified bitumen, plus tile above a minimum slope. Built-up roofing and spray polyurethane foam are marked not permitted over shingles.
An existing built-up roof is the most open base in the table: all six listed materials may go over it, with asphalt shingles and tile only above a minimum slope. Modified bitumen accepts every material except spray foam.
The table governs buildings under that code and sits beside the three exclusions, which still rule some roofs out entirely. For a house, ask how the residential code treats the material you have in mind.
Does going over the old roof get around the cool roof rule?
Not under the state energy code. Its re-roofing rule for single-family homes covers replacements of the exterior surface of existing roofs, and it says outright that adding a new surface layer over the existing one is included.
The rule applies when more than half of the roof is being replaced, and the state defines a roof recover as an extra covering installed over a prepared existing one without removing it. A large recover is measured like a replacement.
Where the state rule reaches depends on climate zone and slope. Los Angeles spans Climate Zones 6, 8 and 9 by ZIP code. Low-sloped roofs fall under the rule in all three, and steep-sloped home roofs in Climate Zones 8 and 9.
The City also keeps a cool roof rule of its own in its Green Building Code. Choose a recover for the condition of the roof, not as a way to sidestep either rule.
What should a recover quote in Los Angeles show?
Start with the layer count. Ask the roofer to check at an edge or through a small opening and to photograph it, because two or more layers end the recover discussion before any number is written down.
Next comes the deck. LADBS, the City’s building department, lists separate express permit lines for re-roofing over existing solid sheathing and over new solid sheathing, so the quote should say which one fits your house.
For a recover, the quote should name the new material, confirm the table allows it over what you have, and explain how the manufacturer’s approved instructions will be followed. A roof replacement quote should show the tear-off and any deck repair instead.
At the end, LADBS uses a re-roofing compliance form, signed by whoever did the work and returned to the inspector. Whichever path you pick, the job is backed by our 5-year labor guarantee.
Talk to us
Not sure how many layers your roof already carries? Call Roofing H USA at (213) 921-3424, tell us the address and the roofing you have, and we will go over what the code allows for your house.