I mentioned this backhoe excavation concept in the beginning of this e-book, but further examination is needed on this subject.
I recently had a discussion with a homeowner who said, “quite honestly, I am talking to many contractors about my home drainage problem, and one particular fellow wants to dig the entire foundation down to the foundation footing right against the wall with his backhoe, for many feet away from the foundaiton, what is your opinion of that method”?
This was my response. I do not believe in that method of groundwater drainage for the following reasons. When I asked the question of the homeowner, “do you experience groundwater entry throughout the year, even when it is not raining”, he replied, “no I do not see any groundwater except when it rains hard”. The answer from the homeowner that the groundwater problem is only evident when it rains hard for a couple of days, tells me that his problem is rainwater caused.
In cases where the homeowners contend that this backhoe solution worked for them, I would remind them that although they do not experience groundwater in their basement as a result, the reason is most likely due to the fact that the soil at the foundation footing is perking the groundwater through the dirt below the foundation footing. This may be enough success for this type of homeowner, but for me it is not success. It is the beginning of a greater problem in the future perhaps, depending on how well the groundwater perks. I would rather pull the groundwater away from the foundation with hand excavated french drains within the surface levels of the soil around the foundation and let the groundwater perk into the soil well away from the home.
I especially do not want groundwater perking under the foundation of my home. This process of perking under the foundation footing or basement floor will sink the foundation stem wall and spot footings if it has a crawlspace, and sometimes crack the basement floor. It is very possible that worse structural damage from this type of construction is in the future for the homeowner. Sometimes it takes awhile, sometimes not.
The guy with the backhoe wants you to believe that the groundwater is coming in below grade all the time due to year round springs and rivers, and that it cannot be collect on the surface around the foundation. When the groundwater is actually rainwater that saturates to that depth because no hand excavated french drains are on the surface levels to vent the groundwater preventing the saturation that causes the groundwater problem below grade in the basement or crawlspace, you are creating the rainwater turned into groundwater into a problem with attempting to remove it in the first place.
According to this fellow, if you dig a huge ditch next to the foundation with no grade or vent, and put a large perforated pipe with a sock around the pipe, the problem will be solved. He will usually backfill the foundation area with dirt, gravel, sand or rock the entire depth to the foundation footing, and about 2-3 feet away from the foundation to the foundation wall. The ditch will not be a french drain or footing drain as he says because it lacks a hard finished clean bottom, straight sides and a grade that will carry the groundwater to a drywell or daylighted vent, which also will not usually be part of his grand plan. He cannot get a man in a ditch 8 feet deep as per OSHA standards without supporting the entire excavation, therefore he cannot make a grade or a clean hard bottom finished with a shovel. He is digging a big fat sloppy ditch.
He wants you to buy into the logic that by letting the groundwater run down along your foundation wall, with or without tar on the foundation wall, the groundwater will soak below grade at the footing and not pool up entering your basement or crawlspace. Sometimes the backhoe guy will not even explain where the groundwater is going because he knows it is not a good idea to perk it under the home unless the footing drain is installed by a professional and all other options to collect the groundwater on the surface layers have been ruled out due to rock around the foundation for many feet and where the homeowner does not want to pay for the excavation of that rock against the foundation and the replacement with dirt that is compacted prior to the installation of hand excavated french drains. If the backhoe deal is done, the groundwater will perk below grade only where the soil content perks well.
If it does not perk well, the groundwater will still back up into the basement or crawlspace. If the ground under the footing does perk the groundwater down, as I have said, you are perking groundwater under your foundation footing or basement floor. Not good.
The backhoe guy will destroy the ability for the groundwater to run off a splash block along the exterior foundation wall to be collected in a french drain that is properly installed.
He will disturb the dirt so badly against the exterior foundation that it will most likely prevent the installation of a hand excavated french drain with optimum performance.
When you do the backhoe deal to your foundation area you will likely also need him to install a sump pump because you will indeed have more groundwater to deal with at or under the foundation or basement floor.
If the groundwater does soak in and you experience less, to no groundwater in your basement or crawlspace, this is both good and bad at the same time, as the groundwater coming off the surface around the foundation during hard rains is actually soaking below the foundation footings or basement floor.
Where did the objective of preventing the groundwater from coming in below grade go? It was already determined that rainwater saturation was causing the groundwater leaking, as the problem did not exist except when it was raining.
I have seen million dollar homes damaged in this fashion. Hand excavated french drains remove huge amounts of weight and groundwater from the top layers of the dirt and prevent the creation of hydrostatic pressure that causes the leaking.
If you are not treating the groundwater by removing it within the top layers of the dirt when it rains, you have no chance to reduce the hydrostatic pressure and you will always have groundwater below grade, even if it appears to be gone and has actually saturated below the foundation footing, as in the case of the backhoe method.
The business of always having groundwater below grade feeds the backhoe guys original contention, because that is what he originally told you, that is the concept he wanted you to buy into from the start. His original contention usually is that there are springs and underground rivers always running groundwater below grade. Protect your budget, your homes infrastructure and your equity from this type of drainage concept.
When you do the backhoe deal, you do not get the benefit of taking soil and clay from the excavation of the drywell and french drain lines to be used in raising and compacting a better grade for run off at the foundation. In fact the grade is destroyed and allows the groundwater to run down the foundation wall through gravel, sand or rock in most cases without any soil to soak up groundwater at all next to the foundation during moderate to light rains.
The reason hand excavated french drains are excavated approximately 18″ from the foundation wall is to allow the creation of the compacted splash block first that I described, against the foundation wall. The objective is to dry out the border of dirt under the splash block from the foundation wall to the inside of the hand excavated french drain all the way down to the foundation footing. When hand excavated french drains are installed, the border between the french drain and the foundation wall will dry out after starving it of groundwater due to the installation of the foundation splash block and the hand excavated french drain.
Hand excavated french drains are your first defense, and in a huge majority of cases, the only groundwater defense needed to prevent groundwater entry below grade.