Hand excavated french drains are the best bang for your buck
When your objective is to prevent rain created groundwater or near surface springs from flooding your homes’ crawlspace or basement, nothing works as well as a hand excavated french drain that has exposed rock on the surface. The hand excavated french drain must be properly located and installed, and free of all debris.
The french drain must be a hand excavated french drain, and have a clean bottom, straight carved sides, with an adequate grade, venting to a daylight vent, sump well, or hand excavated drywell.As I have stated in other articles within this blog, hand excavated french drains as a method of groundwater removal is very old science. For more information on this subject, read other articles in this blog.
The fact is that many times a homeowner will talk to various contractors with ideas on how to approach this groundwater problem, and many definitions of a french drain fly about.
Some contractors will only do sump pumps and advocate pumping the groundwater once it gets into the crawlspace or basement. They may even have a prepared contract that specifies the terms of the sump pump proposal and any interior basement or crawlspace french drains that they say are required.
Another contractor will advocate doing channels, or shallow french drains in the basement or crawlspace prior to doing any groundwater collection with exterior hand excavated french drains on the outside of the home.
Yet another contractor or landscaper will determine that all you need is the ditch witch approach with the perforated pipe and sock over it, and that this method of busting out a trench with broken up sides will work sufficiently to collect and vent your groundwater.
I have seen “would be” home drainage contractors that only owned a backhoe, and some of those contractors would only bid systems that require excavation deep down to the foundation footing if it is a basement groundwater problem.Following the machine excavation they will most often just backfill the trench with rock, dumping rock right on the foundation after placing a perforated pipe along the footing.
They will call this a “footing drain”, but it really is not a footing drain. Why? Usually it does not have a clean and sufficient grade on the bottom for one, and it fails because it does not flow the groundwater away from the foundation to a deeper place where it can perk into the soil, be pumped out, or be connected to a daylighted vent.
Another “why”, is that most cities will have a standard mandating that a drywell where groundwater is collected or placed, be at least 10-20 feet away from the foundation, so why would you collect groundwater that didn’t flow well right on the foundation? Sometimes a footing drain is a good idea, but they must be installed by a professional who knows what they are doing.
You don’t want rock poured on your foundation wall unless it is necessary, as a last resort, and part of a properly constructed and plumbed foundation footing drain that pulls the groundwater away from the foundation area, not just a perforated pipe with a sock over it, laid flat on the outside of the foundation footing that will collect groundwater and allow it to sit there, where it will build up and run deep below grade.
There are spiffy looking plastic devices that lay flat on the outside of the foundation footing which do about nothing. And on and on it goes. The homeowner is dizzy trying to understand the logic behind all those deeply conceptual proposals.
Finally, someone comes along to explain why a hand excavated french drain with exposed rock on the surface, that is engineered to flow the groundwater between depths of approximately 6″-18″ deep to a hand excavated drywell or daylighted vent works much better.
The rain is on the surface when it falls. Most of the groundwater is held up in the top 18″ of the topsoil, whether it is dirt, sand, or clay. If you collect it there, it reduces the degree of saturation more effectively. If you keep adding groundwater to the surface without catching it there, the hydrostatic pressure mounts and then the guy with the sump pump starts looking good when he tells you about all the groundwater below grade that requires pumping.
Well, duh! When you collect groundwater on the surface, you can get so much more, it isn’t even comparable to any other method for results.
If the contractor wants to convince you that the groundwater is coming from underground springs, think about it. In nature, springs run when the rains have saturated the soil. When the rains stop, so do the springs either slow down or stop.
If you do not cut the groundwater off on the surface when it rains hard, the rainwater turned groundwater will keep going deeper as hydrostatic pressure sets in.
If you keep adding weight to the top layers of soil next to your foundation, you will always need that sump pump during periods of rainwater saturation and hydrostatic pressure. “It is a self-fullfilling prophecy”.