The Sorrel Flats water table rises with the first spring melt — digs booked before the thaw are digs done in dry clay. Open-trench week is limited to four houses a season: (555) 033-5902.
The exterior method
Three routes out of a wet basement — ours is the outside one
Seal it where the water lands, carry it away at the footing, and starve it at the surface first. Everything below is what an exterior waterproofing actually is, in the order the water meets it.
The membrane, bonded to the wall
The wall opened to the footing, cleaned and repaired, then wrapped: a dimple sheet that snaps onto a waterproofing coat, creating an air gap the water cannot cross and a path down to the tile. This is the seal — applied to the outside of the wall, where the pressure pushes it on instead of peeling it off.
The tile, at the footing
Perforated pipe on clean stone beside the footing, below the level of the floor slab, pitched to a sump or to daylight. Water arriving at the wall is intercepted before it can push on anything — the drain is what turns hydrostatic pressure from a force into a flow.
The daylight, if the lot allows
A gravity outfall to grade beats a pump in every season but a freeze, and we run one wherever the yard permits. Where it does not, the basin gets the full treatment — sealed lid, battery second pump, alarm — because a discharge with a single moving part is a fair-weather promise.
Services & rates
The dig card
From last season’s opens across Dappleford and the Flats. The $265 survey comes off any dig booked the same year, and every line already contains the sheeting, the spoil haul and the grade put back — topsoil, sod cuts and the flowerbed you photograph before we start.
Full exterior dig & membrane$96 / lin ft
Open to the footing, wall repaired, dimple membrane, weeping tile, stone, backfill
Partial dig — the wet elevation$118 / lin ft
The one wall that takes the weather, tied into existing drainage at both corners
Window wells, drained & domed$340 each
Wells dug to the tile, domed, and fastened so the mulch stays out of the stone
Downspout & sump discharge burial$16 / lin ft
Roof water piped past the backfill to the street or the swale
Sump basin rebuild, sealed & alarmed$1,360 set
Basin relined, lid gasketed, battery secondary, high-water text alarm
The water-path survey$265 flat
Grade, gutters, discharge, tide lines, and which of the three routes the house is asking for
OPEN TRENCH TO CLOSED GRADE · ONE ELEVATION AT A TIME
A dig, in order
Before
The free half, done first
Gutters cleaned and pitched, downspouts extended, the low swale re-graded — a season of that answers more basements than any membrane, and it is where every Underdown job starts whether or not the dig follows.
Day 1
Open the wall
Sod cut and stored, the trench opened by machine and hand-dug at the lines, the wall washed and read: cracks injected, cold joints parged, honeycomb faced. A membrane over unrepaired concrete is a tarp over a hole.
Day 2
Membrane & tile
The dimple sheet snapped to the coat, run from grade to below the footing; stone and pipe laid on pitch, checked with a level every few feet because water reads slope the way a banker reads collateral.
Day 3
Backfill & bury
Clean stone against the membrane, a geotextile so the clay never migrates into it, the spoil conditioned and returned, the discharge buried to daylight or the rebuilt basin, and the surface compacted in lifts.
After
The grade, restored
Topsoil returned, sod relayed the way it was cut, the flowerbed re-planted from the photographs, and the first heavy rain walked together — trench side — to watch the water choose the tile instead of the wall.
The Flats, 2025 — 2026
Opened, sealed, closed
Ten years against water through the wall
If water enters through any part of a wall we opened, membraneed and drained — through the wall, not a floor slab or a window left open — the re-open and the re-seal are ours for ten years, transferable once with the deed. Written against the survey, the photographs of the wall before the membrane hid it, and the pitch readings off the tile.
Two interior systems in eight years, two springs of hauling the shop-vac down the stairs. Underdown opened the north wall, found the original 1920s tile crushed flat as a ribbon, and ran new to daylight. The next April the outfall was a creek and the floor was a floor. I only wish I had called them before the second interior quote.
They dug one elevation — the one the weather actually punishes — and tied it into sound drainage at both corners, instead of the whole-house trench the first bid wanted. The flowerbed they photographed, lifted and relayed has since outgrown the disturbance. That was three seasons ago, and the dehumidifier has been in the loft since.
Before the trench
Fair questions
The five every dig gets asked. The one about the garden is answered in the timeline above — with photographs, not promises.
Exterior dig or interior system — which is right?
Exterior work stops water at the wall and fixes the structure driving it: cracked block, failing parging, a wall that wants the repair anyway. Interior systems manage water that has arrived and never touch the cause. If the wall is sound and the water rises under the floor, an interior drain is honest and cheaper; if the wall itself takes on water, the dig is the only answer that is not a subscription.
What is hydrostatic pressure, actually?
The weight of water-logged soil against your walls. Saturated clay against an eight-foot wall pushes somewhere near a car’s worth of load per tyre-width of footing, and it is what bows walls, opens cold joints and lifts water through slab cracks on the low side. You can pump against the symptom, seal against the pressure — exterior membrane plus tile is the combination that relieves and excludes at once.
How deep — and how close to the neighbour?
To the footing, typically seven to eight feet, in a three-foot working trench; hand-dug at services and property lines, shored where the depth wants it, and never left open overnight without fence and plate. We hand-locate every utility before the machine starts, and the locator’s marks are photographed into your file.
What happens to the garden?
It is photographed, sod is cut in numbered pieces and stored, the flowerbed’s perennials are lifted and heeled in at our yard, and everything goes back the week the trench closes. A rose in the working strip will not survive and we say so before you point at it; everything else has a better season than it deserves.
Why only four open-trench weeks a season?
Because a trench dug in running groundwater is a different, worse job — the wall cannot dry enough to be repaired and membraneed properly, and “properly” is the entire product. Four weeks of dry-clay capacity, booked before the thaw, is the honest number; interior emergencies in the wet season get the interior stop-gap and the dig follows in its week.
The dig, in figures
Pre-thaw bookings for open-trench week close in February · (555) 033-5902 · dig@underdownseal.example
Walk the water home
Tell us where it shows up and when — the tide line, the crack, the hour the pump quit. The $265 survey follows the water from gutter to footing, names the honest route, and comes off any dig that follows. dig@underdownseal.example