Thermal Scans on a Roof Bid: What to Compare Before You Pay

Some roofers now offer a thermal scan as an add-on to an inspection or a replacement bid. The pitch is that an infrared camera can spot water in the roof before it shows up on the ceiling. Sometimes that is true. Sometimes the scan is a short walk, a few photos on a screen, and one line on the invoice. Before you agree to pay for one, you need to know what the camera measures, what conditions it needs, and what the roofer can actually tell you from the results.

What a thermal camera reads on a roof

An infrared camera does not see water. It records surface temperature. Wet insulation, wet decking, and wet shingles tend to hold heat differently than dry ones, so a camera can show a pattern that suggests moisture under the roof. That pattern is a clue. It is not a finding of a leak, and it does not say where the water entered or how long it has been there.

The conditions matter. Thermal readings are useful when there is a clear temperature difference between the wet area and the dry area. In St. Louis that usually means an early morning after a cool night, or an evening after a sunny afternoon, on a day without rain or wind that would cool the roof unevenly. A scan done at midday on a windy day can look busy and still tell you very little. A roof that has been through a winter of freeze and thaw can hold moisture in the decking for days after a warm spell, so the timing of the scan affects what shows up. A scan done right after a storm may also miss the problem if the attic and decking have already dried out.

Roofer comparison: what each bid should say

When two roofers quote the same job, one may include a scan and the other may not. Do not treat the scan as a free bonus or as a sign of extra care. Compare the bids the way you would compare any other line.

• Whether the scan is included in the price, offered as a separate line, or only mentioned in a sales conversation.
• What time of day the scan will be done, and what weather the roofer expects that day.
• Whether the scan covers the whole roof or only the areas the roofer already suspects.
• Whether you receive the raw images with the temperature scale visible, not only a summary.
• Who reads the images, and whether that person writes a report you keep.

A scan that comes with the raw files and a short written note on conditions is a different product from a scan that produces one colored photo with a circle drawn on it. The first lets you check the reasoning. The second asks you to trust it.

What it costs

Scan pricing varies, and the number on a bid is not the whole cost. Ask whether the scan is a separate charge, whether it is bundled into an inspection fee, and whether it is credited toward the repair or replacement if you go ahead. If you do not go ahead, ask whether you keep the images. Some roofers treat the images as part of the inspection file. Others treat them as internal records. Get that answer before the camera comes out.

Also compare the cost against what a scan cannot replace. A scan does not replace a hands-on look at the flashing, the valleys, the pipe boots, and the attic side of the decking. If a roofer proposes a scan in place of those checks, the money is going to the wrong tool. If a roofer proposes a scan on top of a full inspection, the question is whether that extra step changes the scope enough to justify the line.

When you compare totals, put the scan on its own line. Two bids that differ by the price of a scan may describe the same roof with different levels of detail, so check the rest of each bid before deciding which one is cheaper.

What to ask before you agree

1. What temperature difference do you expect, and what weather would make the scan unreliable on the day you plan to do it?
2. Will you give me the original image files and the temperature scale, not only the highlighted photos?
3. Will the report state in writing what the scan can and cannot show?
4. If the scan shows a pattern, what do you check next, and does that check cost extra?
5. Does the scan change the scope of the repair or replacement, and if it does, where does that change appear on the proposal?
6. If the scan shows nothing, is that reported as nothing found, or as a clean result that does not rule out a leak?

A roofer who answers these plainly is giving you something you can compare. A roofer who answers with a sales line is not. Put the questions in writing so the answers come back in writing too. If you want to talk through a specific roof, Keys Roofing can be reached at (314) 220-2333.

What the scan does not decide

A thermal scan does not decide whether a roof is due for replacement. It does not decide whether a repair will hold, and it does not settle who pays for the work. Those answers come from the physical inspection, the age and condition of the materials, and the written scope. A scan can add one piece of evidence. It should not be the whole argument.

Keep the images with the rest of your roof file, dated, with the weather that day written beside them. If the scan later matters to a repair decision, that record will be far easier to read than a memory of what was said on the ladder.