IR scan on flat roof

I had a call today about a flat roof scan on a 10 story hotel. My area had rain off and on for a 4 day period last week Wednesday-Saturday. The rains we had were fairly steady lasting several hours a day. We have had no rain since Saturday. Average daytime highs have been about 50 degrees with lows in the 30’s.

My question is has too much time expired to do an IR Scan or should I wait for the next rain day and schedule for the following afternoon?

I was taught 24 to 48 hours is the optimum time frame but, with an outside ambient only in the 50’s it is possible that some moisture remains depends on the temp on the under side. I did one recently moistue was still visible from the inside about 4 days after a rain but there was no heat on in the building drying it out before I arrived

Yeah, I told him the next day it rained I would call him and set something up for the next day or the following day late in the afternoon depending on the weather.

This will be my first flat roof scan, any pointers? Is there a video online somewhere of a flat roof inspection in action?

Hubert, what is your email address?

it’s info @ just take out the spaces.


You are getting a lot of IR jobs…

You don’t seem to have a clue?? (Sorry)

Are you trained?

Would you like to do my marketing and let me do the IR work?


I went through the InterNACHI Infrared Certified course for home inspections with John McKenna this past Summer. I have done a lot of residential scans, walls, attics, etc but I have not had any large commercial jobs before and was simply asking a few questions. I am sorry if I have insulted you in any way by me asking a couple of questions. I am still learning about the limitations of the camera and simply wanted to know about some weather condition aspects with regards to flat roofs and building height, winds, etc.

Being that I have never done a scan on a flat roof before, I figured I would ask some who had and gain some insight on the tendencies of a flat roof so I could perform a better service for the client. At some point in the past you had to learn and you went on your first inspection and I am no different. The more information I gather and the more inspections I do the better I will become.

Would anyone mind sharing a report of a flat roof with me (with the client info blocked out of course) if so please email it to info @

The way you communicate, it sounds like you need somebody to market for you. (Sorry)

Some of the best IR flat roof information can be found in this standards booklet. Hope this helps.


For your location, insulation in this type of roof is not likely to dry out between rain storms. A bigger concern will be the wind across the roof surface.

For best results, wind speed at roof level should be <15 mph prior to, and during the inspection. Due to their height, mid and high rise buildings often have significant wind across their roofs even when ground level winds are calm.

In addition to the Infraspection Standard mentioned by Andrew McDonald above, you may also wish to check out this Tip of the Week found at our content-based website, IRINFO.ORG:

Feel free to give me a call should you need additional information.

Very truly yours,

Thank you Andrew. That is diffinately helpful.

Jim, Is there somewhere I can get wind data for these heights to assist in scheduling the inspections?


Although I have been performing IR inspections of flat roofs for nearly 24 years, I am unaware of any printed resource that will enable you to accurately predict wind speed at roof level. Simply put, there are too many variables such as proximity to other buildings, building shape, architectural details, presence and height of parapet walls, etc.

My best advice is to pick a day when weather and site conditions are optimal. For a post-sunset inspection perfomed from the outside of the building, these include:

  • Completely dry roof at sunirise
  • Daytime high temps above 40F
  • Mostly sunny day
  • Roof level winds <15mp during daytime and during inspection
  • Temps above freezing during IR inspection

All infrared data should be verified by destructive testing such as core samples or invasive moisture meter readings. Ideally, this should be done at the time of the infrared inspection. Unless you are capable of making permanent repairs, you may wish to engage a competent roofing professional to do this with you.

Should you confirm the presence of subsurface moisture, it is customary to outline the affected areas with spray paint. Thermal imagery along with other pertinent data should be contained in a written report along with a scaled drawing of the subject roof(s) showing the extent of wet insulation and the location of all invasive test sites.

Again, I would invite your attention to the Infraspection Standard for Infrared Inspection of Insulated Roofs. This document outlines the above procedures and requirements in detail and is available for $25 from the Infraspection Online Store.

As a point of information, infrared inspections of roofs is covered in detail in the Infraspection Insitute applications course, Infrared Inspections of Buildings and Roofs. This 16 hour course is available as an open enrollment class or through our Distance Learning Program. This course covers the above information and procedures and is designed to give you all of the information you need to accomplish these inspections successfully.

For more information you are welcome to call me or visit us online at:

Hope this helps.

Thanks Jim.
You always come through with good advice.

Yeah good site , and I saved it this afternoon,unlike the one above it looking to put a hand in my pocket.

Sincerely Jim thank you for your insight and help.

Ditto what Kevin said.

That was a pretty useless reply David.