How to Select Building Materials That Resist Moisture

Floods April 07, 2014|Print


Some materials used in houses are more resistant to moisture, water, flooding, and mold than other materials. Selecting materials that are more suited for contact with floodwaters or water for three days or more without significant damage is important in areas where flooding occurs and hurricanes are possible.

Choose materials based on location, their compatibility with other types of materials, and on how the total components or systems (wall, floor) drain and dry. Although some materials resist floodwater and moisture damage, they may also inhibit drying. Resistance to moisture combined with the ability of the total component to dry is an important consideration.

The following is a partial listing of materials that may resist water and flooding. Before making a selection, consult with the manufacturer about the item's purpose. This listing is not an endorsement of any one product or material. Other materials may be suitable. Check building code requirements.


Moisture-Resistant Flooring Materials

Select moisture-resistant floorings. University of Nebraska-Lincoln, Shirley Niemeyer.

• Concrete materials such as concrete tile, pre-cast concrete, or latex or bituminous formed-in-place can be colored, polished, and sealed.

• Non-porous stone, slate, or cast stone with waterproof mortar.

• Clay tile, quarry tile, terrazzo, or ceramic tile.

• Rubber sheets or tiles.

• Naturally decay-resistant wood subflooring (redwood, cedar, some oaks, bald cypress) or steel for structural members. However, wood can warp. Unless the finished flooring is removed immediately to allow the subfloor to dry, it may become damaged and moldy.

• Solid plastic lumber (may inhibit drying).

• Waterproof mortar or adhesives (may inhibit drying of the subfloor).

• Mastic or silicone, epoxy, or polyurethane formed-in-place.


Moisture-Resistant Wall Materials

• Steel with waterproof applications (coated to resist corrosion); steel studs, beams, and sill plates.

• Solid naturally decay-resistant wood for structural components.

• Cement board.

• Brick.

• Cast stone with waterproof mortar.

• Structural glazed clay tile.

• Ceramic veneer or ceramic wall tile - mortar set, porcelain.

• Concrete.

• Glass blocks or glass panels (may break).

• Plaster with metal lath.

• Natural solid or veneer stone with waterproof grout.

• Artificial non-absorbent solid or veneer stone with waterproof grout.

• Corrosion-resistant metal, metal clad, and vinyl window frames; solid wood window frames in good condition may survive well but are subject to swelling and warping. Interior metal or fiberglass doors. Use impact resistant glass.

• Corrosion-resistant metal exterior doors.

• Rubber mold epoxy polyamide adhesive or latex hydraulic cement.

• Exterior fiber-cement, vinyl, or aluminum siding, brick, or concrete. Lap siding generally permits drying. Brick must be installed correctly and drainage provided so that water and moisture vapor behind the brick can drain and dry. Reinforced poured concrete is strong and has fewer seams than concrete block. Seams may allow water entry.

• Sheathings must be able to dry. Plywood sheathing is strong although it may dry slowly. Oriented strand board (OSB) may swell.

If wallboard must be used, use non paperfaced gypsum wallboard, water resistant fiber-reinforced gypsum wallboard or panels, or cement board. These products may provide more resistance to moisture and mold than regular dry wall faced with paper. Research has indicated that quick-setting joint compound and fiberglass tape may withstand water and flood events better than regular drywall joint compound and paper tape.

Coverings and coatings should allow drying in at least one direction so that interior wall and floor systems can quickly drain and dry. More testing of components or wall systems in actual flood situations and on individual materials is needed.

 

Wall coverings may peel and blister and inhibit drying as seen in research conducted at Tuskegee University. Photos courtesy of H.A. Aglan, PE, Ph.D., Tuskegee University.


Moisture-Resistant Paint, Coatings, and Coverings

• Latex paint will allow moisture in an inner wall or structure behind the surfaces to move through the paint and dry. However, the paint may discolor, blister, and peel.

• Polyester epoxy or other water-resistant coatings are made for specific applications. These may not allow areas such as a wall cavity to dry rapidly and, although easier to clean, may also blister and peel. Although water-resistant strong coatings, oil or alkyd-based paints and enamels may inhibit drying. Read labels for caution and safety warnings.

• Ceramic tile, although resistant to flooding, may inhibit drying of other components.

• Vinyl wall coverings and other plastic-coated paper, paper, and paneling may inhibit wall component drying and may peel and blister. Research (Livengood & Aglan, 2003) has indicated these types of coverings peel and blister.


Coverings and coatings should allow drying in at least one direction so that interior walls and floor systems can quickly drain and dry. More testing on components or wall systems in actual flood situations and on individual materials is needed.


Moisture-Resistant Furnishings

Furnishings, if used and allowed in an area that may flood, should be light weight and easy to move to a higher level if necessary. Some furnishings may be damaged if they move or float in water. Wave action and debris also can damage furniture. Adhesives used in the furniture construction must resist water. Consider these types of furnishings for areas that may flood:

• Metal cabinets and furnishings with rust/corrosion resistant finishes.

• Most plastics.

• Some bamboo or rattan furniture (resists water damage but is subject to mold).

• Concrete and cement.

• Reinforced glass.

• Natural or artificial non-absorbent stone.

Laminated surfaces may separate. Cellulose based furnishings such as paper, cotton, linen, and wood serve as a food source for mold. Built-in furnishings and cabinets may inhibit the draining and drying of the walls behind them, and the surfaces above and below. Built-ins should be opened up and removed to allow the walls to drain and dry.


Moisture-Resistant Insulation

• Foam or closed-cell rigid insulation, including extruded polystyrene or polyisocyanurate, is not damaged by water and resists surface mold growth. This kind of insulation generally allows the wall and floor systems to drain and dry.

• Fiberglass insulation resists water damage and surface mold growth. However, the insulation may trap and hold water and slow drying time of wall and floor systems. Fiberglass insulation usually has to be removed.


Other Materials

• Consider foam-filled metal or foam-filled fiberglass exterior doors. Exterior solid wood or wood panel doors may swell and warp and need several finish coats to protect the surface but may withstand the water better than wood laminated doors.

• Use corrosion-resistant hinges and galvanized or stainless steel nails.

• Mortar and adhesives should resist water.


Summary

Even with water-resistant materials, some damage may occur if a home is flooded. Clean up is necessary and painting and repairs may be needed.

When materials such as tile and plywood are used together, drying time may be reduced. However, water may be trapped behind and under surface materials. Before selecting material combinations for walls and floors, consider length of drying time if water were to be trapped inside the combinations, or in the wall or floor systems. The combination should allow drying in at least one direction. Consider the following questions before you make a final decision. Which way can water drain and dry out? Will the surface material have to be removed from the combination to allow drying? Is the surface material easy to remove to allow drying time? (FEMA Homeowners Guide to Retrofitting.)

 

More Information on Building Materials

Cushman, T. (2006, July/August). Low Country Rx: Wet Floodproofing. Coastal Contractor.

Federal Emergency Management Agency. Build with Flood-Resistant Materials.

Federal Emergency Management Agency. Protecting Your Business from Flooding.

Livengood, S. & Aglan, Heshmat. (2003, Jan/Feb.) After the Flood. Home Energy. pp. 12-16.

Wendt, R. and Alan, H. (2006). Rebuilding Your Flood-Damaged Home. Home Energy pp. 20-26.

York, B. (2006). Safety Measures for Stormy Windows. Home Energy. p. 37.

Zoeller, W. (2006). Designing and Building Hurricane-Resistant Homes. Home Energy. pp. 12-16. or CARB

 


Portions of this information are based on the "Protect Your Home From Flood" by the Institute for Business and Homes Safety and on FEMA Technical Bulletin 2-93 Flood-Resistant Materials Requirements for Buildings Located in Special Flood Hazard Areas. Call 1-800-480-2520 to request the FEMA bulletin.

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