Fluid-applied membranes below grade: getting the thickness right and proving it
The warehouse wall’s spray log has thickness readings but no units or coat identification. The data sheet lists a wet application thickness and a different dry thickness. The reviewer cannot tell whether the crew compared the readings with the right requirement.
Record fluid-applied membrane thickness against the correct wet or dry requirement, using the specified checking method and location reference. Do not compare a fresh wet-film reading directly with a dry-film target. The product source below states different wet and dry thicknesses and calls for wet-gauge checks during application. Its values belong to that product; obtain your system’s actual targets, coat requirements and acceptance method before filling out the log.
Make the readings interpretable
- Separate the requirements on the sheet. Identify the approved wet thickness, dry thickness, coat build-up and detail-area requirements where applicable. Record the units and references explicitly. Do not silently choose the smaller number from a technical table.
- Confirm the field checking method. Have the responsible installer and reviewer agree the project-required method, equipment, timing and checking locations. Arrange qualified checking where needed; a generic gauge routine does not replace the specified acceptance process.
- Locate the work being measured. Link each record to a wall section, application stage and material identification. Include the applicable conditions and installer so a later reader can distinguish a first-coat check from the completed field membrane.
- Record the actual reading. Keep the measured result, units and requirement being compared. Report a deficient or uncertain result instead of changing the entry to the target. Material consumption and appearance can support review but are not automatically the required thickness evidence.
- Resolve thin or questionable areas. Obtain the system’s assessment and correction direction before further coats or covering. Account for its applicable recoat conditions and interfaces rather than assuming any extra pass is permitted at any time.
- Retain the final evidence. Keep the original result, correction reference and required recheck together. Confirm that all required conditions for covering are released; a thickness record alone does not approve cure, details or protection.
Common mistakes
- Comparing wet-film readings directly with a dry-film target.
- Recording only the desired value rather than the measurement.
- Treating pail usage as acceptance when another check is specified.
Checklist
Each thickness record needs
- Approved system, stage and requirement.
- Wet or dry basis and units.
- Specified method and located reading.
- Original deficiencies or uncertainties retained.
- Correction reference and required recheck.
Check your understanding
A wet-gauge result exceeds the dry target. Does that establish acceptance?
