French Drain Service
CCB#219837
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Crawl Space
Prep for install: Locate the area where the drainage system will be installed per the sketch. Look for the highest point and the lowest point of the crawl space. The lowest point will be where the drain ends and the highest is where you want to start the drain.
At the high point, start digging a trench about 4 inches in depth. Trenching towards the low point, you will want to have at least a 1% fall every 10ft.
Installation: once the trench is all dug out, set the perforated sock pipe in the trench (doesn’t matter if you start from the high or low point). Make sure the pipe has a fall/slope, you can do this by using a level or doing a flood test. *Spread the dirt from digging the trench in the crawl away from the trench if you can, otherwise you may have to remove it from the site. Based on the soil, install a thin base layer of clean river rock.
Once the pipe is set and made sure it has fall, backfill the trench with clean river rock.
Tools Needed
- Shovel/hammer/digging pick
- Level
- Bucket(s)
- Hose/nozzle
- Tape measure
Material Needed
- Clean river rock
- Perforated socked pipe
Basement
- Lay down plastic for dirt/concrete to keep the work area clean and organized.
- Mark out where the pipe is to be installed and how much you need to demo.
- Break out the slab 10 inches off the foundation where the drain is going to be installed.
- Dig 4”-6” down from the face of the footing at the starting point and have a 1% fall towards the low point(end).
- Once the trench is all dug out, place a small layer of clean river rock at the base of the trench.
- Set the pipe in the trench and backfill with clean river rock to the bottom of the concrete slab.
- Place drainage/dimple mat 4” up the stem wall and halfway in the trench. Lay 6-mil clear plastic over the top of the dimple mat/ river rock.
- Mix and re-pour concrete, match the existing slab.
- Remove dirt/concrete and clean up.
Tools Needed
- Jackhammer/roto
- Shovel/pickaxe
- Level/tape measure
- Hose/nozzle/bucket
- Mixer w/bit
- Extension cord(s)
- Vacuum
- PPE
Material Needed
- Perforated sock pipe
- Clean river rock
- 6-mil plastic
- Concrete
Exterior
Installing a French drain exterior is similar to a crawl space install. Before digging, make sure you’re not running into any water, gas, or power lines.
- Trench dig exterior where the drain pipe is going to be installed per sketch. The trench should be about 12”-18” deep and 9” wide. The trench should have a 1% fall.
- Depending on what was sold, we will have either a catch basin discharge or a pop-up discharge at the end of the French drain system.
- Once the trench is all prepped, lay down a small base layer of clean river rock.
- Install the basin/pop-up.
- Drill ¼” holes around the bottom and sides of the basin.
- Set the pipe in the trench and make sure it has fall (flood test).
- Connect the pipe to the discharge (pop-up/catch basin).
- Back-fil the trench/ discharge with clean river rock (unless specified, relocate/remove dirt from the site).
- If installing triple wall pipe then landscaping fabric will need to be installed before any river rock is laid down. If installing perforated sock pipe is to be installed, you don’t need the landscape fabric.
Tools Needed
- Shovel/pickaxe
- Tape measure
- Drill/bit(s)
Material Needed
- Pipe (perf socked or triple wall)
- Clean river rock
- Pop-up/catch basin discharge
- Landscape
Related Services
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Foundations First Northwest
Serving the Lake Oswego, OR area. Foundations First Northwest specializes in foundation services and crawl-space issues. Free estimates. Over 20 years of experience. Superior customer service. Call us.
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