Waterproof Your Basement

Most homes are sitting on a treasure trove of useful space: the basement. However, many basements in older homes are damp or leaky, and make unsuitable choices for a new rec room or bedroom. Before you can start any basement remodeling project, you have to keep the water out.

Steps

  1. Evaluate the perimeter of your house. You must ensure that the ground next to your foundation slopes away from the foundation, not towards it. Backfilled dirt around the foundation will typically settle lower than the surrounding dirt causing the ground to sink in and slope towards your house. If necessary, add dirt up against the foundation to create at least a 2" per foot (that is, a drop of 2" for each foot you move away) slope against the foundation. Make sure that the top of the dirt is at least six inches below the sill plate so that there is no ground contact which may cause certain building materials to rot in the future.
  2. on the ground right next to your foundation, you'll have problems. Make sure your gutters are clean, and make sure your downspouts are discharging their water at least {{safesubst:#invoke:convert|convert}} away from your foundation.
  3. Watch out for shrubs and other plants that are too close to your foundation. Rotted roots can create a path for surface water to flow down to your foundation. You should keep plantings at least 12" away from the foundation, and on a slight slope to direct water away from your foundation.
  4. Try to waterproof your walls with a product such as Drylok or Xypex if you have minor, intermittent leaks. Drylok is a waterproofer not a water sealer. It expands as it dries to become part of the wall. Xypex is more like applying a waterproof concrete on the surface that will bond with it. Because Xypex relies on the presence of moisture to form its waterproof crystalline structure, if a Xypex application does have small areas of water leakage they will seal themselves as they cycle through moisture. Xypex is also 2-4 times as expensive as Drylok. The problem with these solutions is that groundwater which is underneath your basement floor or at the bottom of the walls is under significant pressure, due to the weight of groundwater above it pressing down.
  5. Repair defects in poured concrete walls such as cracks and the places where pipes and form tie rods go all the way through the concrete. If you see a crack in a concrete wall it goes all the way through the wall to the outside and is a potential source of water. For cracks that will not experience any thermal or structural movement, DRYLOK Fast Plug is very effective in sealing cracks in the masonry. Another reliable way to repair a wall crack is with an injection of construction-grade epoxy that penetrates the crack all the way from inside to outside, bottom to top. Generally, an experienced crack repair technician is the best choice for this. Do-it-yourself kits of epoxy and polyurethane systems are available, but are less reliable.
  6. Consider installing a sump. This is essentially a hole in your basement floor which contains a pump. When the water level in the sump rises too high, a pump kicks on and draws the water out of the sump, discharging it outside the house, 10 or more feet from the foundation. Installing a sump requires a moderate degree of skill and experience, since you will be jack hammering or otherwise creating a hole in the concrete floor of your basement, excavating a hole, placing a liner in the hole, wiring the sump pump itself, and plumbing an outlet from the pump to the outdoors.
    File:Wikihow basement waterproofing solution.jpg
    Installed sump
  7. Try a French drain (or perimeter drain) for serious water issues. A French drain consists of a continuous system of piping, running beneath the floor of the basement and along the entire perimeter of the basement. Installing a French drain is similar to installing a sump, but requires cutting and removing an approximately 12" wide strip of basement floor along the entire perimeter of the basement, digging a 12" deep trench, filling it with coarse gravel surrounding the drain pipe, then re-pouring a concrete floor to cover it all up. A French drain will always include a sump and pump for removing any water which gets into the drain system.
  8. Have an installer inject Hydroclay around of your foundation. Hydroclay is a waterproofing version of Bentonite Clay, known for its ability to absorb large amounts of water. Usually pumped from the outside, the clay fills in voids and follows the pathways water uses to get inside your foundation permanently sealing the basement. This is the same product used to waterproof tunnels, manholes, dumps, backyard ponds, elevator pits, etc.

Tips

  • Before beginning a serious basement remodeling project, observe your basement carefully during heavy rainstorms. If you can last a year of weather without any water leaks, you're probably going to be OK in the future (so long as you keep those gutters clean and take care of your foundation!).
  • Note that salt & lime deposits form on concrete blocks as water leaks through them (white staining). This MUST be completely removed before any blocker is used. This is the most common reason why the sealing fails. This is generally done by dousing the wall with muriatic acid and scrubbing. Follow this by rinsing the area very liberally with a water hose, then vacuum it off the floor. This will normally take several applications. You will see the muriatic acid react with the deposits on the wall.
  • When installing a sump pump, be sure to refer to local plumbing codes. Most installations will require a one-way valve to prevent water from coming into the sump through the outlet.
  • Battery backup sump pumps are available. Search for "basement watchdog." These are great for sumps that have a steady flow of water into them since you'll know you have a backup if/when the power goes out or the main pump breaks.
  • The construction of a new house is the time to properly seal the house for life. The old standby of plastic wrap and Styrofoam sheeting to protect does work. But it is almost always destroyed during the back-filling of the foundation, causing it to leak. This way of sealing NO LONGER meets the international building code, along with many state, country, or city building codes. The makers of DRYLOK suggest coating the exterior of the foundation with DRYLOK Masonry Waterproofer. Remember the waterproofer is only as good and as sound as the surface. Protect the surface with a wrap before backfilling to protect from rocks and equipment.
  • Regardless of what type of water protection you try to use, FOLLOW THE DIRECTIONS. Common misapplications of Xypex come from not following the directions, or more specifically, contractors being too cheap to do the job correctly. Xypex is at least a two stage system, with the second applications using a thinner, cheaper coating of different composition. Many contractors are trying to offset the cost of Xypex VS Drylok by only applying the FINISHING coats.
    • When cutting into concrete, be sure to tape plastic drop cloths from ceiling to floor to enclose the affected area.
  • When you apply Drylok to an interior block wall expansion joint. The block is hollow. The Drylok will stop the seepage temporary. The block will fill up with water causing bowing walls, mortem separation and wall bowing. Don't try and use these inferior products to seal the expansion joint. It will cost you a boat load of money later , when your foundation starts to cave. This is called a negative pressure. Dig up the outside and apply a positive pressure membrane to stop hydrostatic pressure.

Warnings

  • Mold can be a serious health risk. Keeping your basement dry with a dehumidifier can help.
  • Always wear eye protection and a mask or respirator while cutting concrete.
  • If waterproof paints do not work then you need to first relieve the hydrostatic pressure outside by letting the water in. You can then use an above floor base board system without having to bust up the basement floor.

Things You'll Need

  • chemical splash goggles

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