Hand excavated french drains are installed around the world for land/lot groundwater removal.
Footing drains vented as part of a hand excavated french drain, are one example of the use of hand excavated french drains, as are installations above and below retaining walls, to reduce or eliminate the hydrostatic pressure that builds up behind retaining walls.
Without drainage, retaining walls can fall over when saturated over time.
Groundwater trapped behind retaining walls frequently forces them over within a few decades.
Terraces, slopes, and hillside locations are frequent locations where hand excavated french drains shine, and cannot be duplicated for quality and groundwater removal abilities.
A home or multi-family apartment building foundation should be designed to allow the creation of a compacted home drainage soil grade at the foundation wall, and sloping away from it, of at least 6″ per 10 lineal feet, sloping away from the foundation wall, after the foundation has been poured and backfilled/compacted during the original home construction.
Often foundation vents are poured too low in the foundation wall and then backfilled to the degree that the groundwater just runs right into the hole in the side of the foundation that was created, which is the homes foundation vent, sitting at ground level.
Foundation vents must be poured high enough in the foundation wall to allow the backfilled dirt to be compacted for approximately 18″ from the foundation wall, minimum.
Home owner builders must communicate their wishes to their builder, if they have one, with respect to the installation of home drainage systems, foundation grade required.
Homeowners need to stop digging up their foundation walls to grow plants.
Some of the gardeners reading this are presently cringing at the very thought of having to give up growing flowers and shrubs next to the foundation facing the street, for example.
Many homeowners are caught wondering where the curb appeal of the home from the street is going to come from, without bushes, trees, shrubs and vegetables with flowers planted on the foundation walls.
I am a gardener too. They do grow well along a nice southern foundation wall in early spring. It trashes your foundation though, from a home drainage perspective.
A better way for homeowners to treat their foundation area is to garden in containers and very large pots placed over the french drain 18″ from the foundation wall. Very large pots seldom need to be watered when planted with trees, flowers, everything else. When they do get too full and overflow, or soak from the bottom, they do so over a groundwater removal system with exposed river rock, keeping the foundation dry.
If you plant into containers, you can compact the area at the foundation wall and create a splash block, and cover it with a light covering of bark dust or rock. Notice emphasis on light.
The area where the splash block flattens out from its slope away from the foundation, which is approximately 18″ from the foundation wall, is where the inside of your 12″ wide hand excavated french drain groundwater removal system will be installed.
Most homeowners, before learning about home drainage science, opt to bark dust along the foundation walls, year after year, thinking this will make their weeding easy, to not needed at all.
These areas along the foundation become sponges during heavy rain periods, as they hold groundwater for long periods, days to weeks, to months, as it slowly perks along the foundation wall. Most foundation walls, in the worst of typical cases, never dry out.
Many city building codes in the U.S. require 6 inches of air space from the bottom of the homes siding, to the ground level along the foundation wall, or as the home inspectors around here write it up, ” from any cellulose debris”, which means bark dust, wood chips, and soil too.
The constant wetness along heavily bark dusted foundation areas with existing drainge problems is most often caused by bad grade and loose soil or bark dust at the foundation wall.
It is best to maintain the standard of 6″ of soil grade away from the foundation wall, if you can. Make it a compacted grade and your chances for success increase.
A soil grade increase alone along the exterior foundation wall that corresponds to the leaking area within the inside of the basement or crawl space, when compacted with a hand compactor, will many times prevent or stop the groundwater from running into the crawl space or basement, and prevent the necessity for installing a hand excavated french drain.
Homes that sit below grade to streets are subject to additional rain water runoff from these streets. This can become more of an industrial problem, and neighborhood problem, than a residential one, and should be dealt with through the city or county.
Some developers will construct low point road drains and other groundwater drainage systems as part of the conditions of approval for the subdivision or community. Often however, subdivision conditions of approval are not completed, but yet signed off, due to developers having great connections downtown at the inspectors office.
The conditions of approval for the proposed subdivision are placed on the subdivision developer by the city or county, prior to the developer legally being able to sell any lots.
Only non binding reservations may be taken for the lots prior to the preliminary plat approval and conditions of approval for the subdivision being completed satisfactorily.
Frequently however, these conditions of approval are not adequate, or not meet prior to approval, and homeowners with lots or land that is below grade to ingress and egress roads, could find it neccessary to construct hand excavated french drains, and groundwater venting systems for these french drains, to collect rainwater coming off streets, or have their driveways and lawns, many around million dollar plus homes, washed away from sheets of groundwater flowing off the streets and over the lower home site owned by the unsuspecting homeowners.
When a call to the insurance company and the builder still leaves homeowners with a drainage problem, even after building a new home, producing costly drainage work that they cannot pay for, the game gets full of anger, and rightly so. I would be pissed too.
I installed over $17,000. worth of hand excavated french drain installations for a fishing buddy many years ago, who built a trophy home on top of the hill. Very expensive.
A private 60 acre lake, was part of the gated development.
The streets that wrapped around his 2 acres flooded the entire hillside to the point that even the neighboring vacant hillside home site, slumped and flattened, part of it sliding into the road below and blocking the ingress-egress road to the subdivision.
That could have happened to my buddies home site too, without installing hand excavated french drains during hard early January rains, on tough slopes, with ice and snow as well.
It was close. But in time to save his lawn and home crawl space.
Hand excavated french drains should be constructed and plumbed to collect groundwater within the top 18″ of the saturated soil, where almost all of the groundwater is held up after and during heavy rains.
The objective of the installer, should be to produce a slope of at least 2 inches per 10 lineal feet of grade on the bottom of the hand excavated french drain aqua duct.
Hand excavated french drains should slope at a grade of at least 2″ per 10 lineal feet to the vent, which is either a dry well excavated around 4 feet deep by 4 feet in diameter, or day lighted vent, depending on your topography, and what is possible to accomplish, with respect to the physical uphill locations and limitations.
See additional articles on dry wells, day lighted vents and other types of french drain vents on this web site.
Hand excavated french drains are often installed above berms and terraces, as well as along, in front of, and below foundation walls to prevent the loading of groundwater weight behind the berms, terraces and retaining walls, and to stop the hydrostatic pressure that is caused by the saturation of groundwater behind the retaining wall.
I install hand excavated french drains above and below retaining walls, to prevent them from falling or tilting over, after many years of groundwater soaking, saturation, and freezing behind and under the retaining walls.
Slumping of landscape terraces and hillsides can be prevented if properly installed and plumbed hand excavated french drains are located between the road areas and the walls or terraces that are subject to groundwater damage, caused by hydrostatic pressure from excessive rain accumulation behind the wall.
Add freezing and thawing of groundwater to the equation and the groundwater created, home drainage groundwater damage time, decreases exponentially. It does take buy a few years in some cases.
Nothing forces retaining walls over like freezing and thawing groundwater behind it.
Install hand excavated french drains as part of the retaining wall installation.
The hand excavated exposed river rock french drain installed above the retaining wall should be located around 18″ from the top of the retaining wall, not against it, with a splash block of dirt and clay compacted back to it., away from the wall.