Low & Dry
Built in 1896, Primrose Hall is a lot like other historic buildings you might find on an American college campus today. The North Carolina State University (NCSU) site is a tidy, simple, brick structure, roughly 40 feet square. Its window trim is neatly painted, and at times, the building can seem engulfed by pretty, mature landscaping.
The quaint hall, once the original site of NCSU’s school of agriculture, battled basement leaks earlier this year. As any waterproofing expert knows, basement leaks don’t heal in time, they get worse. So school officials invested about $100,000 with North Carolina-based Baker Roofing Company—also a licensed waterproofing contractor—to trench around the structure and seal the basement walls from the outside.
John McDougall, a Baker project manager, oversaw the job. McDougall’s team used a unique bentonite clay membrane to seal the basement walls from the outside. The bentonite system, when coming into contact with moisture, creates a hardened gel that’s impervious to water, explained McDougall. The reactive waterproofing system also served the job in another way. The last waterproofing effort in the 1960s had an asbestos-based product that the bentonite panels now cover and contain.
“It’s an odd system, but a nice tool when you have a challenging substrate,” McDougall said.
The bentonite system is a practical solution for the Primrose Hall problem. It’s also one of many ways to solve leaky basement issues. Experts admit there are many approaches to waterproofing basements. But in the end, like any contracting job, it comes down to the customer’s expectations, combined with what he or she is willing to pay in order to meet them.
THE BASEMENT PROBLEM CHILD
“Some basements leak, period,” said McDougall. The Pro has seen some rather elaborate internal drainage systems that are designed to manage the amount of water expected to flow into a basement. One system he remembers in the northeast had a ‘false wall’ six inches from the foundation wall that captured the moisture that migrated through the foundation.
“It’s not something I would have in my house, but there are times when all you can do is manage it and deal with it,” he said.
Basements, by their very nature, are water problems waiting to happen. They sit underground, usually eight to 12 feet. Especially in four-season environments, a basement’s walls, which form part of the foundation of a home, are constantly in contact with moisture. There is surface water, which can be seen in the outside yard of a home; capillary water, which is found further underground; and hydrostatic pressure that can be exerted from water beneath the basement floor or in lower levels of the walls, sometimes as a result of a high water table.
During new construction, the outside of basement walls is usually coated with an asphalt membrane. This approach has been used for more than 100 years and satisfies building codes around the country. But it’s the biggest mistake in waterproofing today, argues Charles Boday, an Ohio-based basement waterproofing contractor and certified mold expert with Safe Mold Solutions.
“Asphalt starts to break down in 18 months,” Boday said.
One of the biggest problems he sees in the basement waterproofing business today is old building codes that subscribe to ‘damp-proofing’ standards that simply slow the penetration of water but don’t necessarily stop it.
“You have to remember, building codes give you the absolute minimum when it comes to performance,” he added.
In addition, Boday said basement walls endure plenty of ‘lateral abuse’ with soils expanding and contracting during changing seasons throughout the year.
McDougall often sees asphalt membranes fail because of the shifting soil that cracks the concrete walls. It’s less a failure of the asphalt membrane, he says, and more the structure as a whole. He says many of today’s asphalt membranes have been reformulated to non-moisture soluble levels, and can offer a good waterproofing solution.
Boday and McDougall agree that a good waterproofing effort starts on the outside of the building.
“You want to look at the drainage in the yard and the flow around the house. Is there a downspout dumping water onto the foundation?” McDougall said. “You want to correct those types of things first.”
Experts say downspouts should discharge at least several feet away from the house. Both experts also see their share of situations where the membrane on the outside of the basement walls is failing. When fixing a membrane problem, Boday likes to use the Delta®-MS foundation protection system, a plastic membrane that also creates an air gap between the wall and the dirt coming into contact with it.
Before installing a membrane, Boday also likes to do what he calls ‘foundation restoration.’ The basement wall must be examined closely for cracks, and properly sealed. There are reactive urethane grouts and foam-injection sealers on the market to fix cracks, he says. After cleaning the surface thoroughly and filling in cracks, Boday then uses a surface bonding cement that creates a shell-like layer on the wall to deflect water, before adding the new membrane and backfilling with dirt.
INTERIOR APPROACH, OLDER HOMES
Boday said many builders don’t take necessary precautions with soil cores to mark the seasonal high spot of the area’s water table. The higher the water table the more hydrostatic pressure is exerted on the floor and lower levels of walls, he said. Hydrostatic pressure is measured in psi (pounds per square inch) and tends to increase the lower one digs.
“When the water table is higher than the level of the slab, it’s always going to exert that pressure, and the floor is always going to crack,” he added.
Boday said the only way to work with such situations is to use internal drainage that uses a perforated piping system installed at the end of the slab to catch the water then direct it to a sump pump or a gravitational draining system.
Basements with block walls, in homes built before the 1970s, are notorious for leaking. An interior drainage system in these older homes requires drilling weep holes into the block near the basement floor to help the water drain.
Unfortunately, drilling these holes can be tricky. Through the years, the size of cement blocks changed to smaller designs. Blocks went from being 2-feet long to about 18 inches today. But more importantly, they also went from having five cores to two, Boday explained. Waterproofers often drill weep holes into the wrong areas of a block, missing the core, which could cause water to collect in the area instead of drain into the pipe, he added. “We’ve done waterproofing in 13 or 14 states and have seen that mistake repeated over and over.”
There are plenty of situations where a little basement moisture isn’t a problem. Maybe there isn’t puddling on the floor, but some moisture can be seen on the basement walls. For these situations, today’s interior basement sealers are better than ever.
McDougall stays away from solvent-based formulas that can have a harsh smell. Many will not accept a coat of paint over them either, he says.
“You do want to think about the safety of your employees and the people that are going to use the space,” he added. “Some of those carry very harmful fumes.”
Interior sealer quality is gauged by the psi rating of the product and the guarantee the manufacturer places on it, explains Eric Serrano, a floor and specialty product manager for Behr Process Corporation. And like any other product category, you certainly get what you pay for.
BEHR PREMIUM® Basement & Masonry Waterproofer comes rated up to 12 psi. Behr technical experts say the product far exceeds the average hydrostatic pressure ranges of about 3–5 psi they say are common in basements. Behr technical experts still always recommend using a hydraulic cement product for cracks in mortar joints before applying the sealer.
The product, formulated for basement walls, also has Behr’s proprietary NANOGUARD® technology, which uses smaller particles to create a strong, durable film to help prevent water penetration. The waterproofer also allows for 34 different custom color tints. It’s popular for applications like laundry rooms, basement gyms or recreation rooms.
Often, low-price sealers have fillers that can help fill in small voids in concrete walls, but lack in film quality and ease of application, says Rick Bautista, product marketing manager for Behr Process Corporation’s specialty coatings division.
“Using cheaper fillers like sand tend to bring the price down. Premium products typically use higher quality and more functional ingredients,” he added.
Even with great sealers on the market, McDougall and Boday always try to help customers understand that sealers are not a structural fix or a solution to problems with drainage systems or major membrane failures.
THE NEEDS DETERMINE THE JOB
How a basement space is used will dictate how extensive a waterproofing project may be. Naturally, those who leave a basement unfinished and don’t use the space much are probably a little more tolerant of moisture. Planning on building out that high-end man cave, home theater or great room? Permanent waterproofing approaches are critical. A person who knows what he or she expects from a waterproofing job is usually the happiest customer, McDougall says.
“That’s always a conversation we really like to have up front,” he added. “You have to ask yourself ‘how much is this worth protecting?’”
Keeping a basement space dry starts on the outside of the house. A high-quality membrane barrier applied to the exterior of the basement/foundation wall is the first line of defense against capillary and surface water. Older building codes allowed for damp-proofing standards that merely slowed the penetration of water. But today’s high-quality membrane products do a far better job of actually keeping the water out.
BEHR PREMIUM Basement & Masonry Waterproofer is formulated for waterproofing above- and below-grade basement walls, masonry walls, retaining walls, cinder and concrete blocks, stucco and brick.