Drainage

January 21, 2012

We’re finally having a good winter storm!  We’ve been having drier than normal weather since construction started last month and this was lucky for us.  Up until the arrival of the rain the crew was busy installing a perimeter french drain and ensuring drainage under the house.

As you’ve seen in the photos of earlier posting, excessive water can cause the wood to rot and cause structural problems as well as invite mold to grow.  To prevent water damage and keeping the house dry for comfort we have specified french drain and crawl space sealing.

French Drain
The perimeter french drain was dug down 18″-24″ deep along the perimeter of the house about 16″ away from the foundation.  Mirafi drainage fabric (filter fiber) is used to line the cavity and drainage pipes (perforated PVC) are placed.  Drainage rocks fill the cavity and topped off with soil.  So, when it rains the water will eventually find it’s way into the drainage pipe and the drainage pipe is sloped towards the back to fill the water garden by gravity.  The perimeter french drain helps prevent the water from pooling under the crawl space.

Digging along the perimeter of the house

Note that there are 2 pipes in the trench.  One of the pipe is perforated and will take in water — this is for the french drain.  The other one will be connected to the downspouts to route the water from the roof to the rain water harvesting tank at the corner of the property.  (By the way, the installation of the rainwater tank will be done as a community workshop coordinated through the local Resource Conservation District.  Stay tuned for that workshop in the late summer or early fall!)

Notice the drainage pipe is placed above mirafi fabric and gravel
French drain and rainwater harvesting pipe in the trench leading to back of the yard.

An interesting tidbit:  What’s the origin of the term, “French Drain?”  Well, I initially envisioned some clever drainage system in France.  It turns out the term is attributed to a lawyer named Henry French in Massachusetts who popularized the concept in his 1859 book, “Farm Drainage.”

Crawl Space Work
For a few days the crew got into their jump suits and crawled around to dig out drainage path under the house, install some pipes and sealing the dirt floor with plastic.  They had a cozy work space with lights and music under the floor.

You can see that there is a little carved out channel to direct the water beneath the plastic

Sump pump is installed under the house to pump out any water that pools under the plastic.  Note the electrical line coming out from under the plastic.  The sump pump will eventually be connected to an outlet.

This view is from the cutout in the kitchen floor looking down into the crawlspace

At each pier the plastic liner was taped to the concrete using Siga tape.

View of the sealed crawlspace

Rain Garden Pit
The water from the perimeter french drain as well as any overflow from the rainwater storage tank will go into the rain garden.  This was dug about 5′ deep.  The plastic “thing” (I don’t remember what it’s called) is a way to store larger volume of water than simply having drainage rocks covering the pit.

You can get a sense of the size of the pit with a really tall guy walking in it

When we get to the landscaping stage the area above this pit will have appropriate plants for rain garden.   For now it is covered up with soil and it looks like any other part of the yard.

Rain Garden pit is covered up

Other Work While Digging
Water line and sewage line from the street to the house were also replaced while all the digging was going on.  You just never know what you find when you dig.  The water line from the street to the house was a PEX pipe!  This is a flexible pipe that is used for indoor plumbing but not for external work.  The sewer line was made out of clay.

Fragment of old sewage pipe

About the Author

Chie Kawahara

Chie is one of the co-creator of Midori Haus. When she is not sharing her stories of transforming an old house and giving tours, she enjoys trail running and hiking.

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Rainwater Tanks

Underground rainwter tank is better in garden as source of water system in watering your plants.

underground water tanks

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