Flooring Installer Reports


Writing Reports is Important for the Floor Installer

Checking out floor problems can be a daunting task. Problems may be very obvious (picture above) but the cause could be hard to determine. The floor may be cupped, may have gaps or other defects, but nobody knows what happened. The floor looked great at the time the installation was finished.

An inspector is called in to find the cause for the floor failure. Accusations fly and the floor installer may be blamed for doing a bad job.

Now is the time for the floor installer report to be presented. The condition of the floor when the installation was finished needs to be evaluated. Not only does the installer report protect the floor installer from unwarranted claims, the installer report allows the inspector to find the cause of the problem by comparing measurements obtained now with measurements obtained at the time of the installation.

Dual-depth meters from Lignomat are ideal to document floor conditions: Readings can be obtained at 1/4″ and at 3/4″ deep. The 1/4″ depth reads the top layer, the 3/4″ depth includes the core. Measurements taken at 1/4″ and 3/4″ deep truly pin-point the moisture condition of the floor.

Thermo-Hygrometer or Datalogger BL2 are ideal to document ambient conditions: Use a Thermo-Hygrometer to measure the relative humidity and temperature at the time the moisture readings were taken. Better yet leave a datalogger BL2 on site to record relative humidity and temperature. The BL2 takes 6 readings per day for 8 years. The BL2 graph actually shows EMC.

A installer report of moisture measurements should include several measurements from random locations and also from moisture sensitive areas such as below big windows, in entrance ways, in kitchens, by the sink and by the refrigerator. Note the following for each measurement:

  • Address, name of customer, date
  • Type of floor, wood species, manufacturer of floor and supplier
  • Name of manufacturer of meter
  • Name of moisture meter, measuring mode: pin or scan
  • Settings for wood species and temperature corrections (pin mode only)
  • Settings for measuring depth (scan mode only)
  • Measuring depth for pin, integral pins or external electrode
  • Exact locations where the readings were taken (photo can be helpful)
  • Moisture value
  • Add relative humidity and temperature readings

scanner-moisture-meter-at-window-sill-imageThe photo should show an easy to identify “landmark”: Here a corner with a low window sill and special moldings.  A true measurement should  show the moisture value and the meter settings if possible. It is also important to show the hand pressing the meter against the floor. (When taking a reading pinless meters should be pressed slightly against the surface.)

The Story of Two Pieces of White Oak

When I first started selling moisture meters 28 years ago, many woodworkers asked:Why do I need a moisture meter?

The answer: Because all the hard work, money and time invested, cannot prevent wood from shrinking and expanding, if the moisture content is not right.

To demonstrate shrinkage, I obtained a board of semi-dried White Oak with a moisture content of 18%. Two pieces were cut from the board 4″ long, 1″ wide and about 1/4″ high. One piece was kept at the original 18% moisture content, the other piece was dried down to 6%.

The difference in length was surprising. The large amount of shrinking in the upper piece was attributed to the selected species – the large shrinkage factor of White Oak, and to the orientation of the grain. Notice how the grain runs almost parallel to the length of the board.

Every home has moisture sensitive areas such as entrance ways, kitchens, close to showers, etc. For those areas it is best to use wood with a small shrinkage factor and grain as close to quarter-sawn as possible to reduce shrinkage, in case the ambient conditions change.

Helpful Hints to Prevent Moisture Problems

The challenge of utilizing wood starts with choosing the right wood. The best machining and excellence in workmanship cannot guarantee a high quality product if wood species, grade and moisture content are not suitable for the job. Everybody working with wood has his own unique way of creating masterpieces. Part of his skill is to understand wood. However, the right moisture content is a basic requirement.

Don’t waste time and money on wet wood.

Buying Wood: When ordering lumber specify expected moisture range. Different moisture levels are expected in furniture grade lumber, moldings or lumber lumber. Upon delivery, check the moisture content. Notify the supplier promptly, when the moisture content is not right. If you wait too long, the supplier may not accept any claims and put the blame on improper storage, while the wood was in your care.

Selecting a Wood Species: Not all wood species shrink the same. Check the Internet for the shrinkage factors of the woods you are working with. When mixing different wood species in the same project, select wood with the same shrinkage factors. Unfortunately, more shrinking is always accompanied by more warping. In entranceways, kitchens or bathrooms, it may be advisable to choose more stable floor planks of higher grade to avoid problems. One rule applies to all wood: The more parallel the grain runs to the edges of the board, the less cupping, crowning or warping can be expected.
See Shrinking, Warping

Engineered Floors and Laminated Panels: Engineered wood products can be very stable and not sensitive to moisture changes. The performance of an engineered product depends on the shrinking tendencies of the top layer, while the multi-layered backing is dimensionally stable. Whenever the top layer shrinks too much and the backing does not follow, problems can occur. Depending on the structure, the engineered panel of floor planks may either cup or the top layer delaminates. The wider the floor planks, the more problematic the engineered planks could be.
See Testing of engineered products

Proper Storage: The battle with moisture has not been won when the lumber is dry. Dry lumber should be stored in a closed-in area with a controlled climate, otherwise the dry wood will pick up moisture from the air, if stored in a damp place. Check relative humidity and temperature of the warehouse or other storage areas and compare to the moisture content of the wood. This will show if lumber will change its moisture content while in storage. If the EMC for relative humidity and temperature is the same as the moisture content of the wood, no changes will occur.
See EMC Table.

Proper Acclimation: Manufacturers of wood floors and the NWFA organization suggest allowing time for acclimation before installing a wood floor. Trim, ceiling panels, cabinets and other woodwork should also be allowed to acclimate before being installed. Proper acclimation only takes place when the room conditions are the same as afterwards, when the room is in use. A floor will not acclimate properly when the heat is off, the temperature drops and the humidity is higher than usual. > check out Lignomat’s new EMC data-logger BL2, which records RH,T,GPP,DP,EMC

Restoration: When restoring antiques or repairing furniture, new wood is added to existing woodwork. Make sure to match the moisture contents. Otherwise, shrinking, warping or delamination may occur as the wood equalizes.

Shipping and Moving Furniture: When furniture is moved from a damp shop to an air-conditioned office or from a dry climate zone within the US to a moist climate zone, surface checks may appear within days. Cabinet doors may suddenly not close due to uneven drying. Severe moisture defects can ruin furniture when moving to a new home. To minimize defects make sure that temperature and humidity are slowly adjusted.

Woodwork manufactured overseas will only arrive in good condition here, when the lumber was dried to US standards and packed properly.

Moisture Infiltration from Outside: Excess moisture from outside can come inside through open doors and windows, not properly sealed walls or leaks in the roof. A moisture problem may be noticed when the floor cups, but it could be hard to find out where the problem originated. It is not only bad when the floor cups, it is even worth when mold grows underneath the floor or behind the sheet rock. Moisture trapped anywhere inside a building will migrate into any water absorbing (hygroscopic) materials. If moisture problems appear “out of the blue”, do not start repairing the damage before the source of the problem has been found and eliminated and until all parts of the building have been dried out. Drying out should start immediately to avoid mold built-up. The source of the excess moisture has to be found.

Repair of Moisture Defects: For short moisture intrusion, the damage can be superficial and may disappear after the wood has dried out to its original moisture content. The cause could be seasonal changes. If a floor was not dry at the time of installation or absorbed moisture after installation, cupping or crowning will occur. In some cases the floor can be re-sanded and refinished, but only after is has been confirmed that the source of the problem is eliminated and the floor planks are dry now. If defects are so severe that permanent damage to the structure of the wood has occurred, there is no cure. Therefore, moisture problems have to be avoided before they occur.
See The challenge of Hardwood Floors.

Moisture Measuring and Record Keeping are worthwhile:
Determine the moisture content before you start a job, do not waste time and money on wet wood. Keeping records of your measurements will help when problems occur. Then, you can go back and check the moisture history of the lumber involved. And if nothing else try avoiding making the same mistake again.

For moisture related claims after floor or cabinet installations: In case of complaints the question always comes up, who is to blame. The problem may be very obvious, but the cause for the problem is often hard to find: The home owner turning the air-conditioning off, the cabinet maker or floor supplier delivering products with too much moisture, the installer making mistakes, the contractor not checking the concrete slab, drywall or wood moisture, etc. Taking moisture measurements and keeping records is important until the job is completed.
See Flooring Moisture Report.

For water damage restoration: To get paid for your work, you need records to show the extend of the damage and you need records to show that the problem is no longer there.

Every recorded moisture reading has to indicate the measured value, wood species setting, the moisture meter model, date and location, where the readings were taken.

Why is Mold So Bad?

Green plants make their own food using carbon-dioxyde from air and water through photosynthesis, while producing oxygen. A great blessing for all living creatures.

Mold is not a plant and not an animal.
Mold is a fungi with its own unique “life-style”.

1. Contrary to green plants, the food source for
mold are carbons extracted from the material the mold lives on. As mold extraxts carbon, it destoys the carbon-containing substances: organic materials such as wood, wood-based products as well as plastics made from petroleum products as well as building materials such as concrete and sheetrock. Mold infestations can have catastrophic consequences by weakening or destroying structural elements in buildings.


2. But the destruction of materials
is not all. While digesting its food, mold releases toxic compounds into the air, which present a health hazards to humans living in mold infested houses.

3. And that is still not all. One mold colony can grow millions of spores to reproduce. When the tiny spores are airborne and dispersed throughout a building, they are inhaled by the people living in the building causing coughing, allergic reactions or asthma. People have become seriously ill from living in moldy places. The smell alone can be bad.

Not all fungi are as unwanted as mold. Some are great decomposers, where decomposition is wanted. For example, when trees are dead and slowly turned to earth. Antibiotics such as Penicillin are fungi. Their development has been a blessing for people. Even in our food we welcome the distinctive taste of the yeast-fungi when brewing or baking.

Spores can be found anywhere. Spores need four ingredients to start growing: food (material containing carbons), humidity from water, oxygen from air and moderate temperatures. If all these ingredients are plenty-full available, spores will grow and start new mold colonies. Since we cannot eliminate the air in buildings nor can we eliminate materials containing carbons nor do we want to live in freezing temperatures, we can only try to keep the moisture in materials low enough so that mold cannot develop.

Engineered Floors – Laminated Panels

To save precious hardwoods and create more affordable products, engineered floors and laminated panels have become very popular. Engineered floors consists of a relatively thin layer of hardwood glued onto a backing. The backing can be plywood or some type of fiberboard. Since the backing is invisible, inexpensive softwood or wood fibers are used. One of the first engineered wood was plywood. Plywood is a very stable panel manufactured by gluing several layers of veneer together and changing the orientation of the growth rings with each layer.

Stability: Laminated floors and panels are expected to be at least as stable as a solid piece of wood. And they often are very stable. However, being made from different layers of materials can present a new set of problems. These problems appear mainly, when the moisture is not right to begin with or when the planks are exposed to changes in moisture content.

If the top layer and the backing have the same shrinking tendencies, engineered floors will move just like solid wood floors. If the top layer and the backing shrink differently, then the panel is more moisture sensitive. More shrinking and warping can be expected.

engineered-floorboard-warped-imageWhen the top layer shrinks or expands and the backing does not follow at the same rate, the plank will curl or the panel will delaminate or surface checks appear.

Almost every piece of wood inside a home will endure some moisture movement in the course of a year. Weather and changing seasons affect the relative humidity inside a home and consequently the relative humidity affects the wood moisture in floors, panels or furniture. Small cracks appear and disappear with the changing seasons. This is true for solid and engineered wood. Operating an HVAC year round will stabilize the wood.

Changes of relative humidity are usually followed by changes in wood moisture: For example, when the EMC of air is lower than the wood moisture content (dry winter), the surface and eventually the entire piece of wood dries out until the moisture content has reached the EMC. (Click here for EMC and corresponding relative humidity and temperature.

Wood: When wood is drying out, the surface dries first and shrinks. The wetter core will follow later. Cupping and surface checking can occur. Stresses can build up near the surface and cause the wood to check (small surface cracks). If the deformations are severe enough, the structure of the wood can be broken and the defects are permanent.
Over time, the core will also dry out and the entire piece of wood will have a uniform moisture distribution again. Any cupping may disappear. What may still be noticeable is the overall shrinking and warping due to the change in moisture content. Small gaps between the floor planks may still be visible. Some wood species such as Oak, Sycamore and Beech are highly susceptible to defects from shrinking. Check the Internet for Shrinking Factors.

Engineered Products: When an engineered product dries out, the same drying process occurs as described above. The surface dries out first and shrinks. The hardwood used for the top layer will determine how much shrinking occurs. Since the core is usually very stable, the hardwood layer on top is responsible if any problems occur:

-When the top layer shrinks as little as the core, you have a very stable product (second drawing).

-When the top layer shrinks a lot more than the core, you have a product which will develop problems whenever the moisture changes. That engineered product (first drawing) will only be flat at the manufactured moisture content. The hardwood top will not fit the core at any other moisture content. >Dual-depth meters are ideal for engineered products.

The Challenge of Hardwood Floors

When a once beautiful hardwood floor all of a sudden shows defects, changes in wood moisture are most likely the reason. Even small changes in each board can have a large impact, when hundreds of boards are laid side by side.

Common Causes for Moisture Problems

– Floor planks were not dry at the time of installation.
– Sub floor is too wet.
– Existing or new concrete slab is too wet.
– Water spills and leaks.
– Ambient conditions not right, see EMC Table.

Cracks between hardwood floor planks: Even if the hardwood floor was installed properly and the  floor planks were dry at the time of installation, some wood movement can occur when the relative humidity changes with the seasons. Floor planks may shrink and small cracks appear during the dry winter months with the heat turned on. The cracks disappear during the wetter summer months. Controlling the relative humidity within the room will eliminate this problem.

Cupping: The edges of the floor planks are pulled up and the center remains lower. This happens when the up-side of the floor planks loose moisture and shrink, but the down-side does not follow. It can also happen when the down-side of the floor absorbs moisture from the sub floor and expands. Cupping becomes very obvious when looking across a floor against the light. Minor cupping could be the result from seasonal changes of relative humidity.

floorboard-cupping-imageOften the floor will reabsorb moisture again and flatten out. If the problem is more severe and resanding is considered, be careful. Sanding will leave the edges on the down-side of the floor planks unsupported.

Crowning: The center of the floor planks are higher and the edges lower. This happens when the up-side of the floor planks absorb moisture and expand. Be careful when sanding, because the middle on the down-side of the floor planks will be unsupported.

Buckling: Extreme crowning lifts the floor planks several inches off the sub floor. This is usually caused by a water leak or flood.

One day, a janitor from a nearby school came to the office for a moisture meter. The gymnasium floor had buckled extremely high after a roof leak was not detected during the summer months.

If you are not always present, Lignomat’s remote warning systems can keep track of changes in relative humidity, temperature and wood moisture. Measured values are accessible over the Internet.

Is there a cure for hardwood floors with moisture problems? Minor problems may be caused by seasonal changes. The defects come and go with summer-winter changes. This can only be avoided by operating an HVAC year around. For more severe moisture problems, expensive repair work or replacement may be necessary. Drying out and resanding may help. If the defects are so severe that the structure of the hardwood has been damaged or the wood is permanently distorted there is no cure. The hardwood floor has to be replaced.

Then, nobody wants to take the blame:
The home owner turning the air condition off. The floor supplier delivering wet wood. The contractor / sub-contractor / installer not checking the concrete slab or the sub floor, not acclimating the floor long enough, not installing the floor properly.

As supplier, contractor and floor installer it is important to follow NWFA guide lines and manufacturer’s instructions. Take moisture measurements and keep records – important steps in protecting yourself from unwarranted claims.

Click here for Floor Report
Click here for article in FCI Magazine: How Humidity affects Wood

Shrinking, Warping and Perfect Boards

How much or how little a piece of wood shrinks, depends on the wood species, orientation of growth rings and changes in moisture content.

Differences between Wood Species: Some species such as Oak, Beech and Hickory shrink more than Teak, Mesquite and Cedar. To find the shrinkage factors for different wood species, check the Internet and type: “Shrinkage Factor … ” (followed by the wood species).

Orientation of Wood Grain (Growth Rings): Boards with similar wood grain show similar shrinking and warping tendencies. Otherwise, every board moves different and in most cases unpredictably. The orientation of the growth rings determines the amount of shrinking.

wood-grain-orientations-imageMost shrinkage occurs in the direction of the growth rings – flat grain(white oak sample shown above). Minimal shrinkage occurs across the growth rings – vertical grain or quarter-sawn. Usually boards have mixed grain.


The different shrinkage factors within a board cause warping by pulling the edges and sides of a board in different directions. Cupping, crowning, bowing and twisting occurs or a combination of all four.

Old Growth Lumber versus New Growth: Most lumber available today is second growth from smaller younger trees. Old growth lumber characteristically has tighter growth rings, more evenly spaced and there-fore more stable. The second growth lumber with more space between the growth rings is like a sponge, absorbing and loosing moisture faster.

This is one of the reasons why today more people working with wood are using moisture meters to prevent problems such as loose joints, cupped floors, cracked table tops, foggy finishes.

log-cross-section-wood-grain-imagePerfect Boards: Vertical grain or quarter-sawn boards have straight growth rings parallel to their edges. When changes in moisture content occur, these boards swell and shrink the least and do not warp.

Even if trees would grow perfectly straight, only a small number of quarter-sawn boards can be cut out of a tree. That makes those perfect boards rare and expensive.


Drying: Shrinking, warping and twisting of lumber cannot be avoided during lumber drying. The most careful drying process cannot eliminate these deformations. Once rough sawn lumber has been dried, it will go through the planer to be made into a flat board. If no more changes in moisture content occur the board will remain flat.

Uneven Drying: All of the above described deformations are more severe, when only part of the board changes its moisture content. For instance, if a floor is not dried-out sufficiently, the part of the boards facing the room will dry out faster than the underside facing the subfloor. As a result the floor cups. For more info see The Challenge of Hardwood Floors.

The same can happen when a not-so-dry board is laying overnight on a workbench. During the night the side facing the air is drying out and shrinking. The side facing the workbench is not drying. As a result the board has cupped and can be moved like a teeter-totter. Even after both sides of the board have dried out, the board may not be completely flat and may need to be planed again.

What Causes Moisture Problems?

Wood has always been sensitive to moisture.  It absorbs and looses moisture until an equilibrium with the surrounding air has been reached.  For each wood moisture content there is one specific relative humidity and temperature, when wood does not gain or loose any moisture.  This moisture content is called the EMC (equilibrium moisture content).

Once the EMC has been reached and relative humidity and ambient temperature are not changing, wood is dimensionally stable.  No more shrinking or warping will occur – ideal conditions have been reached.

When wood absorbs and looses moisture below the Fiber Saturation Point (around 25-30%) wood swells or shrinks. To make matters worse shrinking and swelling is often accompanied by warping. Now we have a moisture problem.
See chapter: Shrinking, Warping and the Perfect Board.

Following are examples showing the difference in the equilibrium moisture content (EMC) between dry winters and moist summers:

     At 70°F and 75% relative humidity, wood moisture will reach 14%.
    At 70°F and 35% relative humidity, wood moisture will reach 7%.
    At 70°F and 20% relative humidity, wood moisture will reach 4.5%.

If wood pieces with different moisture contents (some drier, some with more moisture) were placed in a constant climate of 70°F and 35% relative humidity, all pieces would end up with a moisture content of 7%, independent of wood species or initial moisture content. Since in-house conditions are usually between 30-45% relative humidity, the magic moisture content for stable woodwork, furniture and hardwood floors inside a building is 6-8%. See also EMC graph.

Moisture Problems are predictable+Compare wood moisture, relative humidity and ambient temperature with the EMC Chart to find out if wood will absorb moisture, keep its moisture content or loose moisture and shrink:+
– Use a moisture meter to determine the wood moisture content.
– Use a Thermo-Hygrometer to measure relative humidity.
– Use the EMC Table to find the corresponding EMC for the
relative humidity of the surrounding air.No shrinking or warping will occur when the wood moisture and the EMC of the surrounding air are the same. Wood is stable.

Prevent Moisture Problems

Compare wood moisture, relative humidity and ambient temperature with the EMC Chart to find out if wood will absorb moisture, keep its moisture content or loose moisture and shrink:

– Use a moisture meter to determine the wood moisture content.
– Use a Thermo-Hygrometer to measure relative humidity.
– Use the EMC Table to find the corresponding EMC for the
relative humidity of the surrounding air.

No shrinking or warping will occur when the wood moisture and the EMC of the surrounding air are the same. Wood is stable.