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 Exterior Waterproofing:
Note: For a complete video of a deep dig external please see HG TV's Holmes on Homes Flooded foundation episode featuring Basement Technologies Inc. (ie.: our company)
Important Note for Greater Hamilton residents: for greater Hamilton this work requires a permit and a master drain repair license. For Oakville this work does not require a permit, but it does require a master’s drain repair license.
9 out of 10 basements can be repaired from the inside without digging.
 But sometimes exterior excavation is inevitable. If you need it, you need it...it's that simple. The deciding factors tend to be; 1) how extensively is your basement finished (sometimes it can be cost prohibitive to remove wall basement finishing's to perform a repair), or 2) what kind of shape is your foundation wall in (if the blocks are disintegrating, water infiltration is the least of your worries and the structure usually needs to be repaired with exterior excavation). We love to dig, but we take no joy in destroying landscaping, decks, driveways, walkways, and the like. If you need to have your basement excavated we will take all reasonable precautions to protect your landscaping but you will have to get your head around the fact that you will have to do some landscaping when we are done and understand the realities of exterior waterproofing.
The procedure differs somewhat from job to job but the basic procedure is as follows.
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1. Site survey is conducted by a design technician or crew leader to determine where to pile castings (the dirt that comes out of the pit), where we can pile necessary construction materials such as gravel, and where we can safely park trailers, machinery, clean fill bins, and the like. Sometimes we require permission from a neighbor to pile castings on their property to facilitate our work. It is at this time that we decide how the site is to be protected, where we need to plywood protect the ground, and how the site is to managed during the course of the work to facilitate access into the home by the homeowner and crew members if required.
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2. Locates are called in by us and building permit is purchase, if required, and a start week is designated.(we say start week since exterior work can be dependant on mother nature and wet pits can be death traps).
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3. Site prep begins, one of our excavators is dropped on site if the area is machine accessible. Ground protection boards and shoring sections are dropped on site if necessary and excavation commences.
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4. Excavation is completed either by hand or by machine. Shallow digs require no shoring and no slope to the excavated area. Deep digs are either sloped or shored as per WSIB guidelines for safety.
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5. Foundation wall and footing is exposed, scraped or wire brushed, and any visible cracks are filled with hydraulic cement. This is your 1st line of defense
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 6. Then, liquid rubber is applied to the wall which seals every inch of the foundation wall. This is your second line of defense and the job now meets code.
7. But we like redundancy, so we also apply a dimpled sheet air-gap membrane which not only provides you with a third line of defense, but also creates a hydrostatic pressure relief which is how water forces it's way through your foundation wall in the first place.
Note: This may seem excessive, but our motto is do it once, do it well. All of our exterior systems far exceed what is required by the building code but we are also providing a warranty 10 times the length of that which is provided by the new home warranty program!
 8. New weeping tile is then installed. The best approved product presently available for typical residential applications is 4" corrugated pipe with a filter fabric surround. The pipe has slits around the perimeter running the full length of the pipe to admit water, and a filter fabric "sock" to inhibit the ingress of finings or silt. This is important to know since the footing drain is the most important part of any system. The biggest deficiency of a corrugated flexible pipe is than a, it can be crushed during the work, and B, since it is stored in a roll, it has a "memory" and therefore has a tendency to ride up over and above the footing...not good. Therefore, we Basement Technologies installs weeping tile we often use weights and/or pegs to hold it in place and we ensure, prior to the installation of gravel, that the weeping tile is where we want it to be. Even a small rise in any section of a 4" weeping tile can reduce the effective diameter, we pay special attention to this.
9. Once the weeping tile is in place we install an above grade cleanout. This is something that we started doing about 10 years ago to provide above grade access to the weeping tile to facilitate monitoring and maintenance. Again, since we know that the weeping tile is the most important part of your system, AND, the most vulnerable, we spare no expense in providing the means to increase the life expectancy of your install.
 10. Gravel is then installed over the weeping tile. The Ontario building code specifies "not less than 5 and 7/8" of gravel on top and beside the weeping tile (or about 1/2 a foot on top and beside). When calculating our gravel for delivery, we purchase 2 cubic feet per linear foot of weeping tile for our system. This is roughly double that which is required by the building code. Since the purpose of the gravel is to facilitate the functioning of the weeping tile, and we have already agreed that the weeping tile is the most important component of the system, it makes sense to spend a bit more here, while the house is dug up to provide a more robust system.
 11. Filter fabric is then installed over the gravel to prevent silting of the gravel. Since most of the water that enters the gravel drainage layer, and then the weeping tile, comes from above, it makes sense that the water will bring dirt and silt with it as it percolates down through the soil. Over time, the spaces between the gravel that provide the drainage to the weeping tile in the first place, get filled up with dirt. At that point there is little difference between between the gravel on top of your weeping tile and the dirt on top of the gravel...ie.: the gravel might as well not be there any more because it is doing nothing anyways. Installing filter fabric is another way we go the distance to increase the life expectancy of your exterior system.
12. Building inspection is conducted, if required, by a municipal building inspector. The building inspector will be looking for deficiencies in our install that do not meet code as well as checking to ensure that the contractor doing the work possesses the correct licenses. Since our procedures exceed that which is required by the Ontario Building Code, this is ends up being an opportunity for the building inspector for your area to meet any new employees from our company and have a nice chat.
 13. Backfilling and clean up is commenced. Sometimes we backfill with gravel and remove all of the dirt from the property (design technician may specify gravel backfill for various reasons including removal of soil pressure, prevention of settling, or to reduce ponding or frost affects).
14. Removal of extra dirt if required. It stands to reason that if we are installing a quantity of gravel over top of your weeping tile, that gravel will displace a similar quantity of soil. Unless the grade is too low next to the home prior to excavation, all of this dirt will need to be removed. Our default practice is to mound the dirt for natural settlement. Since we create soil voids during excavation, the dirt we place back in the trench is more volumous. A mound will allow for grade to return to close to the original following settlement. It is impossible to calculate the exact settlement following excavation. Homeowners should plan to do some landscaping and final grading following settlement. Basement Technologies offers one free return visit to either bring more fill back to the site or to take additional fill away but only fill relating to our work of course!!!
15. Final clean up is completed and driveway is power washed if required.
The above is an example of an ideal install. This is not always the case. Sometimes corridor digs are done in sections. Sometimes, as is the case with stone foundations, there is a restoration procedure that precludes the above procedure. We offer various upgrades. But the above are the basics of our system
Pros.
- Provides the opportunity for foundation repairs if needed
- Interior finishing's remain untouched
Cons.
- Ground is disturbed and the settling process needs to take place all over again
- Can be very damage intensive with respect to landscaping
- Can be impossible if there is not enough access for excavation
- Expensive
- Work is weather dependant
- System must be maintained. Specifically, the weeping tile must remain functional and must be flushed periodically.
Please contact us for more details »»
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