French drain filter fabric — burrito wrap vs sock vs none
Filter fabric keeps soil fines out of the open-graded #57 stone. A burrito wrap protects the whole stone column (the pro default); a sock wraps only the pipe and clogs faster; no fabric silts up. Order ~20% extra for laps and the top fold (overlap factor 1.20).
What this diagram shows
Three French-drain trench cross-sections compared to show the filter-fabric options. The burrito wrap lines the entire trench with non-woven geotextile, beds the stone and pipe inside, and folds the fabric over the top with about 20 percent extra for the side laps and top fold — the professional default that protects the whole open-graded stone column. The sock option wraps only the pipe, leaving the surrounding stone exposed so soil fines reach it and it clogs faster in clay or silt. With no fabric at all the fines migrate straight into the stone and pipe and the drain silts up. The geotextile (AASHTO M288) lets water through but blocks the fines that would clog an open-graded drain.
French Drain Calculator
Free French drain calculator estimates gravel (yd³ & tons), pipe length, and filter fabric. Get the right trench size, slope, and #57 stone amount.
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