Does my retaining wall need weep holes OR a perforated

Most retaining walls in New Hampshire should have both. Weep holes let trapped water escape through the face of the wall, and a perforated pipe behind the wall (a French drain) carries the bulk of the water away before it ever builds up. They do two different jobs, so the right setup usually uses them together.

Here is what is going on behind your wall. The soil packed in behind a retaining wall is disturbed backfill. It got dug up and put back when the wall went in, so it sits looser and drains slow. Rain and snowmelt soak in and pool against the back of the wall. That water has weight. It pushes. The trade calls it hydrostatic pressure, and it is the number one reason retaining walls lean, bow, or fall over.

Drainage is how you take that pressure away.

A perforated pipe handles the volume. You set it at the base of the wall, behind it, slotted side down or wrapped in fabric, sitting in clean crushed stone. Water moves through the gravel, into the pipe, and runs off to daylight or a drain. That pipe is the workhorse.

Weep holes are the backup. They are small openings through the face of the wall, near the bottom, that give any water still sitting behind the wall a way out. On a segmental block wall the gaps between blocks can act this way. On a poured or solid wall, weep holes get built in on purpose. They are cheap insurance.

So which do you need?

If your wall is short, holds back well-draining sandy soil, and stays bone dry, you may get by with weep holes and a gravel backing. You do not need a full pipe for a low garden wall. We will tell you that if we see it.

If your wall is taller, holds back a slope, or the soil behind it is heavy and wet, you want the perforated pipe doing the heavy lifting with weep holes as a relief valve. NH frost heave makes this matter more here than in warmer states. Water that freezes behind a wall expands and shoves it inward, the same way frost pushes on a foundation. Good drainage keeps the water from sitting there long enough to freeze against the wall.

A quick note on what we do. 603 Basement Solutions is a foundation and basement crew. Retaining-wall drainage and foundation drainage run on the same building science, and the place we control water best is inside your foundation. Our basement waterproofing is the Forever Dry System, a full-perimeter interior drain plus a sump pump, a 12-mil wall vapor barrier, and a dehumidifier. The drain pipe in that system works on the exact principle above. Collect the water low, give it a slope, carry it to a pump, send it out. It is 100% guaranteed to be dry for life!

We do not do exterior excavation waterproofing on foundations. In our field experience that fix tends to fail in a couple of years once the backfill settles again. The durable fix is interior drainage. For a retaining wall the rule is the same. Drain it, do not just seal it.

What drives cost on the foundation side, if your retaining-wall trouble is really a wet basement, is the length of drain you need, your sump setup, and how much wall you cover. A full Forever Dry System runs $3,000 to $30,000. If the water is showing up at the floor wall joint inside, that is a sign your perimeter drainage is overwhelmed, and that is our wheelhouse.

If you are not sure whether your wall problem is a landscaping fix or a foundation problem, get eyes on it. Our inspection is free, the estimate is free, and you get a quote within 24 hours.

We serve New Hampshire, Maine, and Massachusetts. Trusted by 5,000+ homeowners in New England, rated 4.9 across 257 Google reviews, BBB A+ accredited, licensed and insured. Read the 603 guarantee for how we stand behind the work.

Call us at 603-610-1770 or book your free inspection and we will tell you straight what your wall needs.

Related questions

Can a bad retaining wall cause a wet basement? It can, if the wall sits near the house and dumps water toward the foundation. Water pooling against your foundation soaks the disturbed backfill and finds its way in at the floor wall joint. The interior fix is our basement waterproofing system.

Does a perforated pipe go above or below the soil behind a wall? At the base of the wall, behind it, sitting in clean crushed stone, sloped to drain to daylight. Cover it with gravel, not bare dirt, so silt does not clog it.

Should I waterproof my foundation from the outside instead? We do not recommend exterior excavation waterproofing. In our experience it fails in roughly two to three years as the backfill resettles. Interior drainage lasts. See our structural and foundation repair and foundation repair pages.

My basement wall is bowing inward, not a retaining wall. What now? That is frost and soil pressure on the foundation. We stabilize bowing walls with carbon-fiber straps, a power brace, or helical piers depending on the wall. Carbon-fiber straps run $850 each and a power brace runs $1,300 per brace. See supplemental support.