Checking substrate moisture — practical guidance and quality checks
The measurement must be made using a method appropriate to the substrate and compared to the manufacturer's limit of the finishing material. Base your control on agreed standard, measurement and documentation, not just visual impression.
In brief
The measurement must be made using a method appropriate to the substrate and compared to the finishing material manufacturer's limit.
Base the inspection on the agreed standard, measurements and documentation, not solely on the visual impression.
What is controlled
The "Substrate moisture control" process is used to obtain a load-bearing substrate that is clean, dry, even and compliant with the requirements of the next layer.
When to check
Perform the "Control of substrate moisture" check before covering the work, installing subsequent elements, making the final payment or starting use.
Defects visible only after covering should be checked at inter-stage inspections.
Documents and conditions of receipt
Before starting, prepare: assessment of adhesion, moisture, absorbency, evenness and type of existing layers.
Control Tools
Typical materials and auxiliary elements: repair compounds, leveling mortars, cleaning and degreasing agents, crack strengthening materials.
Typical tools and equipment: spatula and scraper, sander with suction, level or patch, moisture meter matched to the substrate, vacuum cleaner industrial.
How to check
- Establish acceptance criteria based on the contract, design, instructions and agreed standard.
- Provide conditions for defects to be seen without artificial exaggeration or concealment.
- Inspect the surface visually, then perform measurements and functional tests.
- Record any discrepancies with the location, photo, meaning and expected method of repair.
- Make a decision on acceptance, conditional acceptance or refusal for a specific scope.
Conditions for reliable reception
Carry out the "Control of substrate moisture" inspection in conditions similar to those of normal use and with lighting that allows you to assess the effect without artificially hiding or exaggerating defects.
Record the measurements along with the place, tool and conditions control.
Acceptance Criteria
Perform the inspection in conditions appropriate for subsequent use and before covering the work with another layer.
- the device and method match the material
- the measurement covers potentially humid zones
- the result, date and conditions are recorded
- the substrate is load-bearing, clean and free from layers limiting adhesion
Limits of self-control
Dust from old layers can be harmful. Limit its spread, use suction and respiratory protection. Do not sand material of unknown composition until it has been identified.
Common reception errors
- relying on touch
- comparing the results of different methods without correction
- covering active moisture
- applying new layers on dust, grease, weak paint or damp substrate
Difficulty, time and risk of errors
Partial, conditional and final acceptance
The substrate can be repaired locally, completely leveled or a new system solution can be created. The least invasive method only makes sense if the layers left behind are truly load-bearing.
What to do with the check result
After preparing the substrate, apply the appropriate priming or layer provided by the system. Do not allow other works to re-dirty and damage the received surface.
Frequently asked questions
What does “Substrate moisture control” involve?
The measurement must be made using a method appropriate to the substrate and compared to the manufacturer's limit of the finishing material. Base your inspection on agreed standard, measurement and documentation, not solely on visual impression.
What needs to be prepared before the "Substrate moisture control" stage?
Before starting, prepare: assessment of adhesion, moisture, absorbency, evenness and type of existing layers.
How can you verify that “Substrate moisture control” has been done properly?
Apply in conditions suitable for subsequent use and before covering the work with another layer. • the device and method match the material • the measurement covers potentially wet zones • the result, date and conditions are recorded • the substrate is load-bearing, clean and free from layers limiting adhesion
When is a specialist needed for "Subfloor moisture control"?
A specialist is needed when measuring installations, tightness, structure, humidity requiring interpretation and wherever an incorrect reception may hide a technical defect.