The Importance of Using Drainage Rock
Drainage rock, sometimes called drain rock or gravel pack, plays a vital role in many construction projects. This coarse gravel material allows water drainage and prevents subsurface erosion. Drainage rock is typically angular crushed stone between 1 and 3 inches in diameter. Using the right type of drainage rock and installing it properly ensures effective long-term performance.
Choosing the Best Size Stone
- 1-1/2 inch drainage gravel works well for footer drains, French drains, septic systems.
- 2 to 3 inch gravel is ideal for retaining walls, gabions, diversion ditches, beds under paver driveways.
- The rock should be uniformly graded for proper void spacing and drainage.
- Avoid rounded river rock which does not compact and drain well.
Washed vs Unwashed Gravel
Washed drainage rock has been screened to remove all fines and dust. This leaves only the larger particles and creates better drainage void spacing. Unwashed gravel contains more fines that can clog up over time. Washed gravel costs a bit more but provides superior performance and longevity.
Key Applications for Drainage Rock
- Base of retaining walls and gabion walls. 4-6 inches recommended.
- Window well drainage. 6 inches minimum depth.
- Foundation perimeter drainage and footer drains. Surround with filter fabric.
- Landscaping areas prone to erosion. Line beds with landscape fabric.
- Underneath gravel driveways and pathways. Compact and slope for drainage.
- Septic system leach fields. Size per local regulations.
- Temporary diversion ditches and channels. Line with geo-textile first.
Tips for Proper Installation
- Prepare subsurface by compacting soft soils to prevent settling.
- Install non-woven geotextile fabric below rock to maintain separation.
- Mound landscape fabric 6-12 inches above final grade to create a reservoir.
- Tamp rock in lifts of 4-6 inches for compaction.
- Slope drainage channels and beds away from structures at 1:100 minimum.
- Follow all local regulations and permit requirements.
Using the right gravel and following proven construction methods will ensure proper drainage and water management on any building project.