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Crawl Space Waterproofing

Basement Waterproofing
Crawl Space Waterproofing
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Crawl Space Waterproofing

People constantly ask, “What is the purpose of a crawl space?” First, the foundation footing needs to be below the frost line. Maryland, 30”-36”, in Virginia, 24”-30” – and if the builder doesn’t want to spend a little extra creating a basement, a crawl space is what you have.. Crawl spaces offer an efficient, expedient access to substructures, pipes, and a few other areas that may be difficult to reach otherwise; access to conduits, electrical, plumbing, ducts from the HVAC, and other such maintenance, repair, and installation needs.In essence, a crawlspace, as its name implies, is a variation of a basement in which one crawls around. Some are 3’ to 4’ in height, while others tend to be as low as a foot in height. Occasionally we encounter a concrete floor, but more often the floor surface is just dirt or gravel, sometimes with a thin piece of plastic on top, which is supposed to act as a vapor barrier.

Residential Waterproofing and Vapor Proofing of the Crawl Space

To begin with, as foundation experts, we would like to establish the correct method of moisture control in crawl spaces and dispel the old, obsolete theories and guidelines regarding crawl space ventilation, under floor insulation, and moisture control. We are now in the 21st Century and it is time for our construction industry to move into this Century as well. Innovations and new technological advances in construction, foundations, and basement waterproofing have spread to these same advances in crawl space waterproofing and moisture control.

For decades, because it was mandated by the International Residential Code, contractors, home builders, municipal building inspectors, and homeowners alike have believed (or been led to believe) that a crawl space needs to have exterior vents on opposing walls. The original intention of these vents was so that air may flow through a crawl space, from one vent to the other. The theory here is that this will draw out any extra humidity from the enclosed space.

In fact, many crawl space vent and vent fan manufacturers would have you continue this belief. However, recent studies show that vents in a crawl space actually create a very different effect, which is known and now accepted as the ‘Stack Effect’. Stack effect is defined as the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, and is driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences.

The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the ‘chimney effect’, and it helps drive natural ventilation and infiltration. Since buildings are not completely or hermetically sealed (at the very minimum, there is always a ground level entrance), the stack effect causes air infiltration.

During the warmer seasons, the warmer indoor air rises up through the home or building and escapes at the top, either through open windows, or through leakage. The rising warm air reduces the pressure in the base of the building, forcing cold air to infiltrate through either open doors, windows, or other openings and leakage. During the cooling season, the stack effect is reversed, but is typically weaker due to lower temperature differences.

As a result, the cold and humidity (and mold spores and dust) from the crawl space are drawn into your home, increasing your heating costs and endangering your well-being. Ironically, the better you ventilate your crawl space, the more heat is drawn out of your home through upstairs cracks. Even in warm weather, when there is no vertical air flow drawing cold air up into your house and hot air out the upstairs, ventilating both ends of the space doesn’t actually do much for airflow or humidity.

There is nothing to draw the air through the vents, if they are both at the same level. In addition, the ventilation approach really amounts to treating the symptoms instead of curing the illness – and not doing a very good job at that. The disease, in this case, is excessive air and moisture entering the crawl space, which attracts the mold, rodents, termites, and other pest problems, along with increased condensation and excess heat transfer during colder months between the crawl space and the outdoors.

To reiterate what we said earlier, you might find that your builder, home and municipal inspectors disagree with this idea of sealing and insulating a crawl space. It goes against their conventional wisdom and it contravenes many local building codes that were written from that accepted wisdom. I had a long time convincing my ex-partner – a master carpenter, custom homebuilder– so convincing you may be difficult. Nevertheless, this is the truth.

You might still think that running a space heater in your crawl space will leave you with warmer feet. But you will improve the indoor air quality of your home and crawl space, resolve any moisture, mold, or rotting wood problems down below, make your whole home healthier, cut heat, air conditioning, and energy loss, and save money… IF you set this out-of-date belief aside and go with what tons of research and experience suggests is the most effective method of dealing with crawl spaces. (We have research papers and references available if you still disbelieve and would like to call and discuss this further.)

The The Foundation Expert Crawl Space System creates a dry and sanitary closed environment, providing a safe area for your storage needs, while improving the overall indoor air quality of your entire home.

The Foundation Expert Crawl Space System

Drainpipe and Sump Pump

If you need drainage, then we first dig a trench around the perimeter of the foundation, inside the crawl space, and install a sub-floor pressure relief system. This system is comprised of 4” Drain Pipe, in a deep, wide trench of round washed gravel, with weep holes drilled into the concrete block to bleed any water, which has accumulated. We then place a Miradrain® wall drainage mat to allow continual drainage, and we then backfill to the surface with more gravel. The drain pipe leads to a sump pump, which will then discharge the water outside and away from the crawl space.

Crawl Space Sealing Drain Fabric

We then install over the floor a Sealing Drain Fabric

  • 100 mil thick
  • Prevents liner from “sticking” to soil
  • Enhances water drainage beneath liner
  • 100% polypropylene fibers – won’t rot or decay
  • Cushions floor – protects liner, hands and knees

Crawl Space Sealing Floor Liner

Once the Sealing Floor Drain Fabric is installed, over top of that we place a 22 mil Multi-Ply Floor Liner, completely covering the entire crawlspace floor.

  • Specially formulated rubber based adhesive system
  • Seals out moisture and soil gases
  • Unaffected by storage items and human traffic

22 mil Multi-ply Floor Liner

  • 100% pure virgin resins
  • Seals out moisture and soil gases
  • Antimicrobial – Won’t support mold growth
  • Class A / Class 1 fire rated
  • Nylon reinforced – won’t rip, rot or decay
  • 25 year manufacturer warranty

Permanent Seaming Tape

We seal the 22 mil Sealing Floor Liner with a 9 mil, white poly, 4″ wide, permanent seaming tape.

  • 4″ wide, pressure sensitive, 9 mil white poly
  • Specially formulated rubber based adhesive system
  • Seals out moisture and soil gases
  • Unaffected by storage items and human traffic

Crawl Space Waterproof Insulating Blanket

We then cover the walls with our Crawl Space Waterproof Spray Insulation or

We use an Insulating Blanket.

  • 60 mil Class A / Class 1 fire rated
  • Insulates wall – reduces energy costs
  • Won’t support mold growth
  • Seals out water vapor and radon gas
  • 99% pure aluminum backing
  • No nesting support for pest and rodents

Roll Adhesive

  • Attaches insulation blanket to wall
  • Seals floor liner to floor supports and pipes
  • Never dries out, provides an air tight seal
  • Non-toxic, USDA approved for indirect food contact

The Foundation Expert Crawl Space System turns murky, nasty, wet spaces into a dry and sanitary closed environment, providing a safe area for your storage needs, while improving the overall IAQ (indoor air quality) of your entire home. For more information, please call The Foundation Expert today at (703) 762-2429.