Over the past 30 years, Nusite Group Contractors has performed several hundred interior and exterior basement waterproofing jobs all over Toronto and the surrounding GTA. Homeowners that have wet or leaky basements are often confused as to how the waterproofing process works. While in some cases, an interior waterproofing job is sufficient, often times it will not mask the underlying water problems surrounding your foundation. In this case, exterior waterproofing is your best bet for doing the job once and for all.
When a basement foundation needs to be waterproofed, a series of steps must be followed sequentially to do it correctly. All repairs and prep work has to be completed before the membrane is applied. The membrane must be made from a quality material. In our case, we use Bakor Waterproofing, which is a superior product and provides excellent and long lasting protection for the basement exterior foundation to prevent further leaks or seepage.
Here are the steps which we take to waterproof a basement foundation.
#1 Excavate the Basement Foundation
Normally, we excavate the area around the home by hand. We do this because mainly to minimize any potential damage which machinery might cause. However, if it is possible to use machinery to complete the excavation faster, we will do so.
The basement foundation will be excavated down to the footing so the basement walls are completely exposed. We will excavate down to the level of the weeping tiles, or the lowest point of the footings to ensure the footings are at the correct depth. Shoring will be used in some situations to prevent the possibility of a cave-in.
Then, we will use a combination of wire brushing and power washing (only if the wall is a concrete foundation) to clean off the dirt so we can properly evaluate any existing damage to the foundation walls. Once the state and condition of the footings and the foundation of walls has been evaluated, we will begin our repair.
#2 Basement Foundation Repairs
First, we manually chisel out any visible cracks or gaps in the foundation wall. These gaps and cracks are then filled with a hydraulic concrete to fill all the voids.
Some basement walls may still be rough and uneven. To properly and effectively apply the sealant membrane, we may have to apply a parging coat to properly smooth the walls which may require up to 2 coats. The parging acts as a means to damp proof the foundation walls along with providing a more consistent medium to apply the waterproofing membrane.
#3 Apply the Waterproofing Membrane
The next step is to apply one of two types of membrane sealants which will be either Aquabloc 720-38 or CM-100 series liquid membrane. Different types of membrane material are required for different types of foundation walls. The important thing to remember is that a waterproofing membrane is the only cost effective and most efficient way to waterproof the exterior basement foundation walls, as some competitors will employ cheaper methods which in fact only damp proof the wall. This approach is far less effective than the waterproofing materials that we use.
The waterproofing material is applied to every square inch of the foundation walls. This membrane is the primary material which waterproofs the foundation walls and prevents water from entering.
The membrane then requires a mesh to hold the material and keep and cracks or gaps effectively sealed. The mesh we use to use reinforce the waterproofing membrane is Yellow Jacket mesh which adheres to the membrane.
#4 Apply a Drainage Board Membrane
The next step is to apply a drainage board membrane to the exterior of the waterproofing membrane. This secondary membrane acts as your first defense against water and frost and also protects the waterproofing membrane when the excavated foundation is filled back in.
The drainage board membrane is a dimple board membrane. The dimpling effect provides a space between the waterproofed walls so the dimple membrane has an air space which allows any water that enters the air space to drain effectively to the weeping tile.
After the dimple membrane is applied, it is then sully sealed along the seams. The dimple membrane is then finished with a termination strip at the top of the membrane to tightly seal the membrane and affix it to the wall. We then apply concrete anchors to effectively secure the dimple membrane along the termination strips.
#5 Weeping Tile Steps
Effective drainage is very important to keeping a basement waterproofed, so addressing the weeping tile is the next step which is equally vital to the process because water needs a place to go. There are many different types and sizes of material used for weeping tile.
Regardless of the weeping tile you currently have, it should be replaced with the best possible material. New technology now exists for a more durable and more efficient weeping tile. The weeping tile we usually use is a new form of perforated plastic tile that is covered with a sock. The purpose of the sock is to prevent sand from entering and clogging the tile which make drianage ineffective.
Once the weeping tile is replaced, we then cover it with a landscape fabric and then a clear layer of 6 – 12 inch stones. One thing to keep in mind is that if you also have a window that is within 6 inches of the top of the level grade (meaning after the excavated hole is back-filled), you will also require the installation of a vertical drain which is attached to the weeping tile to ensure effective drainage of any water which might seep in around the window.
#6 Backfilling the Excavated Basement Hole
This is the final step to the process and should also be done correctly as it is simply not enough to push the excavated material back into the hole. A compactor must be used to properly tamp down the earth and done in such a manner to avoid any possible damage to gas lines or other underground utility connections. Proper backfilling also allows for proper grading which must be sloped away from the house. It also ensures there are no larger piles of dirt that needs to be settled.
The landscaping can also be repaired by us afterwards, but you should be aware that it can take up to 3 months before the dirt fully settles.
So these are the steps taken when performing an exterior basement waterproofing project. It may seem like alot of work, and it is, but many times it’s the only way to ensure you can enjoy a healthy and dry basement. To have such a big project performed successfully, make sure the contractor you use is fully qualified and licensed and is using the highest quality materials for the job. As you can see from these steps, it’s not something you’d want to have to do again. Have questions about basement waterproofing? Contact us here, we’re happy to help!
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