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Effects of Moisture on Materials

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To develop a drying theory, you must know how moisture affects various types of materials.  The two major variables in determining the extent of moisture damage to materials are permeance and exposure time.  The permeance factor of the material refers to how readily it absorbs moisture.  Exposure time refers to how long it was exposed to moisture.

The reason water damage restoration professionals must respond quickly when water intrudes into structures is to reduce exposure time.  The faster the water is removed, the less primary and secondary damage will normally occur.  Water damages the various types of structural materials in different ways, and water damage restoration professionals should learn the effects of water in order to better assess damages and provide accurate restoration estimates.


When wood absorbs moisture, it expands.  Under certain conditions this expansion can result in warping or buckling of the wood.  The grain in the wood may cause it to expand at different rates, resulting in warping.  If no space between different pieces of wood exists (in a floor, for example), the wood buckles at the joints where the boards meet or at the walls.  The extent of warping or buckling depends on how much moisture is absorbed and the type of wood.  Warping and buckling may be permanent even after the wood dries.  Floors must be replaced if these irregularities cannot be removed by sanding or refinishing.

Particle board, plywood and Oriented Strand Board (OSB) are durable enough to withstand some exposure to moisture during the dry-down process.  These woods, however, are susceptible to water damage.  They are put together with exterior glues (resin-type glues), and if the glue is dissolved or damaged by water, the integrity of these materials is affected.  The materials and types of adhesives used in plywood, as well as the way plywood is constructed, make it more resistant to water than particle board.  However, plywood may delaminate, particle board and OSB may disintegrate, all three can swell, warp and buckle.

Moisture affects the wood framing of many structures.  In rare situations, stud walls, floor joists and ceiling rafters might warp to the point they must be replaced.

Finishes on wood affect both absorption and evaporation.  The porosity of the wood's surface varies depending on the kind of finish, whether wax, polyurethane, polymer, lacquer, or latex enamel paints with a gloss, semi-gloss or satin finish.  The finish can slow the rate of moisture absorption by making the wood's surface less porous.  yet, if wood materials somehow absorb moisture beneath the finish, evaporation of moisture will be slower.

Wood Strip Flooring/Hardwood Floors

Wood floors cannot absorb large amounts of moisture without warping or bowing.  If the wood bows to a concave shape with the edges slightly raised, the effect (which is called "cupping") can often be sanded out.  If the bowed shape is convex, with a hump in the middle, the effect (called "crowning") is generally not possible to sand out.

Water on hardwood flooring must be extracted immediately, and wet carpet and pads installed over the hardwoodfloors should be removed.  Finished wood flooring sometimes returns to its original shape after drying, eliminating the need for replacement.  Floors should not be sanded until they are completely dry, since any drying that occurs after a sanding process could cause bowing to return.

Parquet and Laminated Block

Laminated floors swell quickly and rise in hills and valleys.  Often the floor must be replaced if a good quality flooring company cannot make repairs.  If the damage consists of water stains only, parquet often can be sanded and refinished: laminated block normally cannot.


Painted concrete may flake or blister, requiring scraping, etching and repainting.  If the paint contains lead, a hazardous waste, use a qualified subcontractor to remove the paint.  Concrete floors can mildew and should be treated with an appropriate disinfectant.  Sometimes, moisture moving through cinder blocks or porous concrete can leave chalk-like calcium deposit on the surface.

Resilient Asphalt Tile

Asphalt tile is the only material recommended for use below grade on concrete slabs.  It will usually maintain a good bond with concrete following water damage.  White or chalky areas respond well to cleaning with stripper, steel wool and an abrasive scouring powder.  The whitening is caused by the separation of sealer wax or finish from the floor itself.  Test by scraping with a pocketknife.  If the white material scrapes off, it normally can be removed by stripping.

Some asphalt tile and vinyl tile may contain asbestos, and some glues used to adhere tile contains asbestos.  If in doubt, have the glues and tile tested to determine if they contain asbestos.  Using a certified asbestos abatement contractor to remove glue or tile containing asbestos.

Vinyl tile on concrete is not as durable as asphalt.  It will usually come loose if a great deal of water is involved.  The migration of water coming up through concrete, leaving white, chalky depsoits can also force tile to separate from the floor.  Since vinyl tiles come up easily from concrete, replacing them is less troublesome than replacing asphalt tiles. 

When resilient tile or yard goods are installed over plywood, particle board or celotex underlayments, the finished floor is frequently damaged as a result of warping or deterioration of subfloor.  If water migrates to the subfloor though seams or around the floor boundary, the flooring tiles may need to be replaced, since you will not be able to dry the subfloor through the moisture barrier formed by the tiles.  Swollen particle board underneath resilient flooring normally must be replaced.

Ceramic Tile

Ceramic tile and grouted joints are normally waterproofed when installed over plywood, but any cracks make them vulnerable to water damage.  Warping or expansion of the subfloor causes the tiles to break apart at the joints and come loose.  Replacement of the tiles is required after the subfloor is repaired.


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Jan 09, 2011 08:34 PM