What questions should I ask a garage floor coating installer in St. Louis before signing?

St. Louis garage slabs carry one of the widest ranges of pour vintage in the country, from 1880s Soulard and Lafayette Square stock built when the city's brick-yard concrete industry was still inventing itself, to 2020s pads in Chesterfield and O'Fallon. The Mississippi River valley climate adds Gulf moisture for nine months a year, MoDOT runs one of the heaviest deicing salt programs in the Midwest, and freeze-thaw cycling between November and March is constant. Vetting a coating installer in this metro requires questions that account for all of it. Use the list below before anyone signs you to a bid.

The slab walk is the first question

Ask whether the installer will walk your slab in person before quoting. A measurement from a phone call or an aerial photo is not a real bid in St. Louis, where slab condition varies dramatically between a Tower Grove South 1900s pour and a Chesterfield 2015 pad. A serious installer comes to your address, examines the concrete, identifies the diagonal cracking patterns from clay subgrade movement, checks for the salt scaling that accumulates over decades on the city's older floors, and notes any moisture indicators from the river valley humidity. If the first response is a square-foot number sight unseen, that is the first signal to keep looking.

The guide on what goes into a garage floor coating project walks through the seven variables an honest installer considers. Use it as a benchmark against what different bidders tell you about your St. Louis floor.

The questions, sequenced for a St. Louis slab

1. Will you diamond-grind the slab, or are you etching? Acid etching is the shortcut that still shows up on many St. Louis bids. It cannot reach the mechanical profile a coating bond requires, particularly on the older urban slabs where decades of laitance, paint, and contamination have accumulated. Diamond grinding does. An installer who tells you etching works on a Soulard 1890s slab is selling you a coating that will fail in the first humid summer.
2. What basecoat product and topcoat product will you use, by name and chemistry? The right answer is high-solids epoxy basecoat with aliphatic polyaspartic topcoat. Vague terms like "industrial system" or "premium grade" without product names usually point to a low-grade install dressed up as professional work.
3. How will you handle moisture testing on a slab in this climate? The Mississippi and Missouri River confluence keeps relative humidity elevated through most of the year, and many St. Louis slabs sit on subgrade that carries seasonal moisture. The right answer involves calcium chloride testing or a relative humidity probe before the basecoat goes down. The wrong answer dismisses moisture as not relevant in residential work.
4. What is your crack repair scope, and how do you differentiate between crack types? Hairline networks get low-viscosity epoxy injection. Wider cracks with ongoing clay-driven movement get flexible polyurea. Spalled perimeter zones get structural patching. An installer who treats every crack the same way leaves you with a floor that fails at the moving cracks within two winters.
5. Are you Verified by the Amazing Garage Floors network, or operating independently? Verification means documented protocol, manufacturer-backed product specifications, and a Limited 15 Year Warranty behind the work. The independent installer market in the St. Louis metro is broad and uneven, and there is no quick way to tell a competent crew from a poor one without that documented backing.

The warranty conversation in writing

Ask for the warranty in writing before you sign, and read what it excludes. Many low-bid St. Louis warranties exclude hot tire pickup, UV yellowing, edge peeling, and any moisture-related failure, which together account for the vast majority of failure modes in this climate. A warranty that excludes those is a warranty on a floor that will fail and not be covered.

What to read for specifically in the fine print

• Hot tire pickup, the most common failure mode in St. Louis summers. The post on hot tire marks on a garage floor covers why this matters.
• UV yellowing on garage doors that face south or west and see direct afternoon sun.
• Edge peeling at the threshold, where MoDOT brine residue and freeze-thaw cycling concentrate together.
• "Moisture-related" failure exclusions, which can be applied broadly enough to disclaim any failure on a slab in a humid metro.

The Amazing Garage Floors Limited 15 Year Warranty covers the coating system without those exclusions for the most common failure modes. That is the standard against which every St. Louis bid should be measured.

Installation day questions

Ask what installation day actually looks like in your garage. A real one-day install in a St. Louis residential bay runs diamond grinding, full crack and spall repair, basecoat application, full vinyl flake broadcast, and polyaspartic topcoat all in sequence. Ask how many crew members will be on site. Ask whether they will move stored items or whether you need to clear the garage the night before. Ask what time they arrive and what time they typically finish.

Ask about return-to-service. A properly installed polyaspartic floor in St. Louis is walk-ready that evening or next morning, with vehicle traffic acceptable in roughly 72 hours. An installer who tells you the floor needs a week is either using the wrong chemistry or hedging against a product that does not perform in humid conditions.

The historic-stock question for older neighborhoods

If your home is in Lafayette Square, The Hill, Tower Grove South, or another historic neighborhood with brick-yard era concrete, ask the installer specifically about their experience with century-old slabs. Many of these floors were poured before air-entrainment additives became standard, which means every freeze-thaw cycle over the slab's life has applied full pressure to the concrete matrix. The damage is real, but it is repairable when the installer recognizes what they are looking at. An installer whose portfolio is mostly new-construction Chesterfield or O'Fallon work may not have the diagnostic experience for an 1890s urban slab.

References specific to St. Louis, broken out by neighborhood type

Ask for references from completed installations in both halves of the metro: a historic city neighborhood and a newer suburb. An installer with a portfolio limited to one or the other has not proven their work across the full range of slab conditions St. Louis presents. Driving by a completed installation in Kirkwood or Chesterfield and seeing the floor through a garage door window in person is a reasonable thing to ask for.

The DIY-versus-professional question, asked honestly

If you are still weighing a hardware-store kit against professional installation, ask the installer to walk you through the tradeoffs. A serious one will tell you honestly when a kit makes sense, short-term rental, property flip, detached shed without UV exposure, and when it does not. The post on DIY epoxy garage floor kits covers the comparison in detail. An installer who insists every floor must be professional regardless of use is selling, not advising.

The St. Louis-specific path forward

The bid you sign should come from a verified crew that walked your specific slab, identified the prep scope honestly, named the product chemistry, and put a real Limited 15 Year Warranty in writing. Schedule the free on-site assessment, ask the questions above, and compare the answers carefully before committing. The river valley climate is unforgiving of corner-cutting, and getting the coating right the first time is cheaper than getting it right the second time after the first attempt failed.