Roof Replacement in St. Louis

Roofs in greater St. Louis usually come off for one of two reasons: age or weather. Missouri's Department of Commerce and Insurance says the useful life of a roof is usually about 25 years, and one bad hail spring can end a roof well before that.

Replacing a roof here also means working through a patchwork of rules. Missouri has no statewide residential building code, so the requirements come from your city or county, and across the river the roofer needs an Illinois license. Below: the limits on roofing over an old layer, the code items a new roof needs, how permits vary from town to town, what a replacement costs in this region, and how the job runs.

Replace or repair: how to tell

A leak on its own is not a reason to replace a roof. One split pipe boot, a strip of wind-lifted shingles or a worn chimney flashing is repair work, and if that is all your roof needs, that is what we will tell you (see roof repair). Replacement makes sense when the trouble covers the whole surface:

Age. A roof in its twenties is near the end of the useful life Missouri's insurance department describes. Have it looked at before the next storm season, not after.
Wear on every slope. Curled or cupped shingles, blisters, and large bare patches where the granules are gone. The FORTIFIED program of the Insurance Institute for Business & Home Safety lists each as a sign a roof may be due.
A deck that gives. Sheathing that flexes in several places will not hold nails well, and new shingles over it will not sit flat.
Hail on every side. Bruises scattered across several slopes are rarely a patch job; see storm damage.
Two layers already. If the house was roofed over once, the next roof starts from bare wood.

Tear-off or a second layer: what the code allows

Laying new shingles over old ones (the code calls it a roof recover) saves the cost of the tear-off and very little else. Section R908.3 of the International Residential Code says a replacement strips all existing roofing down to the deck. St. Louis County's re-roofing checklist, which governs unincorporated areas and the cities that contract with the county for inspections, allows a recover in one case only: a single existing layer that is not water-soaked or deteriorated (the county cites R908.3.1.1), on framing strong enough to carry two roofs. The plan reviewer may ask for an engineer's calculations to prove it.

Illinois puts a similar limit in its roofing license law. The definition of a roof recover in 225 ILCS 335 leaves out water-soaked or deteriorated roofs, slate and tile, and roofs that already carry two or more layers; that last one can be lifted only by a structural report from an Illinois-licensed architect or engineer that the state has accepted.

The products push back too. The Asphalt Roofing Manufacturers Association notes that most shingle makers do not recommend new shingles over laminated ones, and Owens Corning's instructions for its Duration STORM and FLEX lines require the old covering and underlayment to come off first. We strip every replacement to the deck, since that is the one moment in a roof's life when anyone can see the wood.

Worker on a ladder stripping worn asphalt shingles to expose the wooden roof deck

A new roof, layer by layer

The cut-away drawing on this page numbers the eight parts of the shingle roof we put back. Working up from the framing, here is what each does and what a written quote should say about it:

Rafters. They stay put on an ordinary replacement. A cracked or sagging rafter makes it structural work, and St. Louis County wants structural changes drawn and sealed by a Missouri-registered engineer or architect.
Deck. Plywood, OSB or old boards. The county accepts board decking with gaps up to 1/2 inch and wants panels at least 3/8 inch thick over anything wider.
Drip edge. Metal trim along the eaves and rakes that runs at least 2 inches onto the deck.
Ice-and-water membrane. A self-sticking sheet at the eaves and in the valleys, the two places backed-up water reaches first.
Underlayment. The sheet over the rest of the deck. Ours is synthetic.
Starter course. An adhesive strip under the first row, so the bottom edge is glued down from day one.
Shingles. Architectural, six nails apiece. Choosing a line is its own decision; see roof shingles.
Ridge vent. The attic's exhaust, which only works with enough intake low on the roof. The roof ventilation page does the math.

Ridge vent — exhaust at the peak, matched to intake at the eaves so the attic can breathe.
Architectural shingles — fastened to the manufacturer's pattern, six nails a shingle.
Starter strip — the sealed first course at the eaves, so wind cannot get under the edge.
Synthetic underlayment — the second line of defense if water ever gets past a shingle.
Ice-and-water shield — self-sealing membrane at the eaves and valleys, where ice dams back water up.
Drip edge — metal along the edge that steers water into the gutter, not behind it.
Roof deck — walked board by board; soft or rotten sheathing is replaced first.
Rafters — the frame the whole roof sits on.

What the code asks of a new roof here

Missouri leaves building codes to local government, and the spread is wide: Creve Coeur enforces the 2009 International Residential Code, while Brentwood has adopted the 2024 edition. The St. Louis roofing code guide covers the regional design figures. On a shingle replacement, these are the lines that do the work:

Underlayment. St. Louis County's checklist, citing R905.1.1, calls for one layer of Type I felt or an approved equivalent on slopes of 4 in 12 and steeper, and two layers from 2 in 12 up to 4 in 12. Shingles are not allowed below 2 in 12.
Ice barrier. R905.1.2 requires one only where a jurisdiction has a history of ice backing water up at the eaves. St. Peters lists none required in its design table, and the county checklist agrees. We put the membrane in at eaves and valleys anyway.
Nails. The code floor is four per strip shingle (R905.2.6), a minimum the Department of Energy's Building America guide repeats. Manufacturers reward more: Owens Corning rates its Oakridge shingle for 110 mph with four nails and 130 mph only with six plus its starter strips. We nail six.
Edges and walls. Drip edge at eaves and rakes (R905.2.8.5), and step flashing where a slope meets a sidewall (R905.2.8.3).
Ventilation. On a re-roof, the county wants attic ventilation checked against Section R806 and corrected if it falls short.

Permits: it depends on the address

Whether a re-roof needs a permit changes at city limits. A few examples, taken from each jurisdiction's own published rules:

Where	Re-roof permit rule
St. Louis City	Not needed for like-for-like material with no more than 25% of the sheathing replaced; needed beyond that
Unincorporated St. Louis County	Needed when the slope is under 4 in 12, more than 25% of the sheathing is replaced, the material changes, or board decking has to be covered with panels; a like-for-like shingle job at 4 in 12 or steeper is exempt
Town and Country	Needed for every roof replacement
St. Charles	Replacing shingles is listed among jobs that generally need no permit
Columbia, IL	No permit, but the roofer must hold an Illinois license

Many cities publish no answer. We check with the building department before work starts and pull whatever is required. Kirkwood, Webster Groves, Ballwin, Brentwood and Wentzville also want contractors licensed or registered with the city first. Every city's rule is on its own page under roofing by city.

What a roof replacement costs in this region

The most useful public price check is Zonda's 2025 Cost vs. Value Report, published by the Journal of Light Construction. Missouri sits in its West North Central region. Both roofing projects assume a 3,000-square-foot hip roof torn off to bare sheathing, with flashing at two skylights and a vented ridge:

Report project, 2025	Job cost, West North Central	Added resale value	Cost recouped
Asphalt shingles, new underlayment, galvanized drip edge	$30,693	$16,650	54.2%
Standing-seam metal, perimeter ice barrier, synthetic underlayment	$50,520	$22,527	44.6%

Illinois falls in the report's East North Central region, where the same asphalt job is listed at $29,253 and the metal job at $47,473. These are model houses, not a quote for yours. What moves a real price:

Size and pitch: more squares cost more, and steep slopes go slower.
Layers to strip and wood to replace, which nobody can count until the tear-off.
Valleys, dormers, chimneys and skylights, each one more flashing to build.
The material: a shingle line, metal, or a low section that needs a flat-roof membrane.
Code catch-up, such as attic ventilation or an exhaust duct the inspector wants fixed.

How the job runs, start to finish

Measure and inspect. We measure the roof from aerial imagery, then climb it and photograph every slope and penetration. You keep the photos either way.
Written scope. One line-itemed proposal with every material named by brand and product. The number on it is the number.
Permit. Pulled by us wherever the city requires one.
Tear-off. Landscaping gets tarped, and the old layers come off down to the deck.
Deck. Every sheet or board gets walked; soft or rotted sections are cut out and replaced.
Install. Drip edge, membrane along the eaves and in the valleys, synthetic underlayment over the rest, starter, shingles at six nails each, new flashing, and a ridge vent with intake to match.
Cleanup. The site is tidied daily, and a magnet goes over the yard before the crew leaves. One crew stays on your roof from start to finish.
Close-out. Finished photos come to you, and the manufacturer's warranty is registered.

Ask what happens to bad wood. On any quote, find the line that covers rotten sheathing. Nobody can see that cost from the ground, and it is the line most likely to start an argument.

Licenses and contracts on both sides of the river

There is no state roofing license in Missouri; where contractor registration exists, a city runs it. Illinois is different. Under the Roofing Industry Licensing Act (225 ILCS 335), a company that roofs for pay there needs a license from the Department of Financial and Professional Regulation, limited (homes of eight units or fewer) or unlimited, and Section 11 tells permit officials to see it before issuing a permit.

The same act sets out what an Illinois roofing contract must say before work begins: scope and materials, approximate dates, the contractor's street address and insurer, a clause letting you rescind within 72 hours for a full refund of any deposit, and a statement that the contractor cannot pay or waive your insurance deductible. Section 5.5 also has the contractor hold your payments in trust until materials arrive or most of the work is done.

In Missouri, the statute aimed at roofing contracts is RSMo 407.725, for jobs paid through an insurance claim; the storm damage page explains the cancellation right it gives you.

Common questions about roof replacement in St. Louis

How much does a new roof cost in St. Louis?

The 2025 Cost vs. Value Report lists $30,693 to replace a 3,000-square-foot asphalt shingle roof in the West North Central region, which includes Missouri, and $50,520 for standing-seam metal. Your price depends on size, pitch, layers, rotten decking and flashing, so we inspect first and then give you one written number.

Can new shingles go over my old roof?

Only in narrow cases. St. Louis County allows a second layer just over one existing layer that is dry and sound, on framing that can carry both. A roof that already has two layers has to come off. Many shingle makers advise against layering over architectural shingles, and our replacements always start from the bare deck.

Does a re-roof need a city permit?

It depends on the city. St. Louis City skips the permit for like-for-like work that replaces no more than a quarter of the sheathing, while Town and Country requires one for every roof replacement. We confirm the rule with your building department and pull any permit ourselves.

Is ice-and-water shield required in St. Louis?

Usually not by code. The residential code calls for an ice barrier only where a jurisdiction has a history of ice dams at the eaves, and both St. Peters and St. Louis County list it as not required. We still install it at the eaves and in the valleys on every replacement.

Does my roofer need a license?

In Illinois, yes. The state licenses roofing contractors under 225 ILCS 335, and an Illinois roofing contract must include a 72-hour cancellation clause with a full deposit refund. Missouri has no state roofing license, though cities such as Kirkwood and Wentzville require contractors to hold a city license or register first.

Will a new roof pay for itself when I sell?

Not by the report's numbers. In the West North Central region, the 2025 Cost vs. Value Report estimates that an asphalt roof replacement recoups 54.2 percent of its cost at resale and a metal roof 44.6 percent. The bigger return is a dry house.

Where we work

Roof replacement across greater St. Louis, from the city and St. Louis County out to St. Charles, Jefferson and Franklin Counties and across the river into the Metro East. Each city has its own page with the permit rule and code edition that apply there: