How To Construct a Mold-Safe
Home or Commercial Building
consultants Phillip Fry and Divine Montero, Certified Environmental Hygienists,
Certified Mold Inspectors, and Certified Mold Remediators
June 22, 2012. Mold infestation in a new home or commercial building is
common. New building mold infestation problems can cause severe health
problems for occupants as well as substantially reduce the fair market value
of the structure because moldy homes and buildings are difficult to sell or
To construct a mold-safe house or commercial building, follow these twenty-one
mold prevention recommendations from mold experts Phillip Fry and Divine
Environmental Hygienists, Certified Mold Inspectors, and Certified Mold
Remediators. Mr. Fry is the author of the mold advice ebook Do-It-Best-Yourself Mold
Prevention, Inspection, Testing, and Remediation, available at
1. Prior to blueprint drafting, obtain the advice and suggestions of a mold
prevention consultant to include the most effective water intrusion and mold
prevention strategies in building design, selection of building materials,
and construction techniques. “The key to mold control is moisture control,”
advises the U.S. Environmental Protection Agency (EPA).
2. Make sure that the building lot and its landscaping grading are downward
and away from the building to keep rain and surface water from entering the
building foundations, basement walls, concrete floors, and crawl space
3. Install a thick, high quality moisture barrier (with no holes from
negligent installation) beneath any concrete floor slab or basement concrete
floor to stop water from wicking up from the ground into the concrete, and
thus into flooring materials and walls resting on the wet concrete. Do not
use regular plastic sheeting as a moisture barrier because such sheeting is
easily damaged in installation, and it usually suffers physical degradation
over time---thus allowing water penetration and upward wicking in the
4. Add adequate amounts of top-quality waterproofing compound into the
concrete mix to transform the entire concrete floor or slab into an
effective water barrier. Also, thoroughly waterproof the exterior of
basement walls and of the building foundations.
5. Dry thoroughly (30 days) the concrete floors and concrete/masonry walls
prior to adding wood building components. New concrete floors hold hundreds
of gallons of water. Most of this water usually dries to the inside of the
house or building if the wood building components are installed prior to
complete concrete drying, according to the Nova Scotia (Canada) Department
6. Do not install plumbing supply lines into concrete slabs or floors,
wherein the lines usually degrade and start leaking in twenty years or
less. Hire the most capable plumber to install the best quality plumbing
lines, fittings, and equipment. Concentrate all plumbing lines and sewer
drain lines in as few areas as possible, with large, easy access panels for
the monitoring, maintenance, and repair of plumbing components.
7. Minimize the potential for water damage from frozen, broken pipes by
insulating water supply lines (in the attic, crawlspaces, garage, and
exterior walls), protecting exposed outdoor faucets, and sealing gaps in
8. Use a hidden moisture meter to scan the ceilings, walls, and floors of
all plumbing areas for water leaks prior to building occupancy, and on a
regular basis thereafter.
9. Use steel framing components instead of wood (delicious food for mold to
eat and grow with) to build the walls, second floor, attic, and roof of the
building. Although steel framing is a little more expensive than wood, it is
very affordable long-term, especially in consideration of steel’s water
damage and mold prevention qualities, as well as fire resistance.
10. Alternatively, build the walls out of poured concrete, concrete blocks,
or insulated concrete building components. Use adequate amounts of
waterproofing compound in both the concrete and in cement stucco interior
and exterior finishes. Build weep holes into the exterior
masonry walls. Weep holes are openings at the foundation level of a brick or
concrete block wall that allow moisture to escape from behind and inside the
wall. Do not close or block these openings.
11. If the owner or builder uses any wood timbers, plywood, plywood
substitutes, drywall, plasterboard, and ceiling tiles, pre-inspect such
cellulose-based materials for mold growth and mold stains prior to their
use. Remove the mold completely from the materials or return the materials
to the supplier, and replace with mold-free materials. Use a moisture meter
to scan all wood for moisture content, which should not significantly exceed
16 to 17 percent. Cellulose is the main substance in the
cell walls of plants (and thus of wood from trees), and it is used in the
manufacture of the paper backing of insulation, artificial fibers (e.g., for
carpeting and padding), and many building materials such as drywall,
plasterboard, and plywood substitutes.
12. Protect all wood timber, plywood, drywall, and other cellulose-based
materials by spraying them on all sides and edges with boric acid powder or
Tim-Bor (which also prevents termites).
13. Install a high-quality rubber water barrier beneath the roof shingles or
tiles to keep rain from entering the building should there be degradation
of, or damage to, the shingles or tiles. Install gutters (with leaf-catching
screens) that lead to in-ground pipes that take rainwater away from the
14. During construction, store all mold-vulnerable, on-site building
materials off the ground and beneath waterproof tarps or plastic sheeting to
protect the materials against rain, and thus against mold growth.
15. During rain and as a precaution at the end of each construction day,
cover the entire building with waterproof tarps or plastic sheeting to keep
rain off of the building until the roof has been shingled, and the siding
and windows have been installed.
16. Prevent construction defects that allow water entry into the home or
building by carefully monitoring the day-to-day construction of the
structure. A construction-savvy owner, a trained employee of the building’s
architect, or an independent physical engineer or home inspector should do
this important construction quality control monitoring. Construction
defects are an important cause of mold infestation.
17. Design the heating/ventilating/air conditioning (hvac) system to have in
its return air duct a built-in mass media (6 inches or thicker), replaceable
hepa filter, or a top-rated electronic air cleaner to remove continually
airborne mold spores from the circulating air.
18. Install a programmable dehumidifier into the hvac to reduce indoor
humidity to a mold-discouraging sixty percent or less. Do not install a
moisture-increasing humidifier. Install a humidistat-controlled exhaust fan
in the attic and any crawl space area to help keep the humidity level low in
those areas. Install exhaust fans that vent directly outdoors in the
bathrooms and kitchen.
19. Do not use wall-to-wall carpeting because carpeting and padding are
great mold food and a great place for mold growth, viruses, bacteria, and
dust mites to hide and to multiple. Instead, for concrete floors, use
ceramic tile set in cement containing a waterproofing compound. Use colored
cement with waterproofing as the tile grout. For wood floors, install vinyl
tile or linoleum. Use washable area rugs for comfort and beauty.
20. Use only windows that are double-glazed (two sheets of glass with an air
vacuum in between) to insulate effectively your home and to reduce
mold-causing water condensation on the indoor (room-side) glass surface.
21. During construction and also upon completion prior to sale, rental, and
occupancy, the building should be inspected and mold tested all-around for
mold problems by a Certified Mold Inspector or Certified Mold Remediator, or
have all cellulose-based surfaces and the insides of heating/cooling
equipment and ducts mold tested with mold test kits, available at
For free answers to your mold questions and problems, please email mold
expert Phillip Fry
phone (480) 310-7970, and visit Mr. Fry’s
mold information websites: