Foundation Waterproofing in Flagstaff, Arizona

Flagstaff · Coconino County

Foundation waterproofing in Flagstaff is the least glamorous work we do and by a wide margin the most valuable per dollar. If you called us about a crack, a sinking corner, or a wet crawlspace, we will spend part of the visit walking the outside of your house looking at where water goes. That walk usually explains everything.

Flagstaff's water year, and why it is hard on foundations

People hear Arizona and picture drainage as a non-issue. Flagstaff runs on a different calendar than the rest of the state.

Winter: accumulation

Snow arrives starting in November and accumulates. It does not run off the way rain does. It piles up around the house, on the roof, and wherever the plow and the shovel put it, and it sits there.

March and April: the melt

This is the dangerous season. Months of accumulated snow releases over a few weeks. The ground is still partly frozen near the surface, so infiltration is poor, and the meltwater runs along the surface and into whatever low spot it finds. If that low spot is against your stem wall, your foundation soil is saturated for weeks at a stretch. That is a longer sustained saturation event than most humid-climate homes ever see.

May and June: bone dry

The driest stretch of the year. Clay soils that swelled in April now shrink. Anything that got wet and expanded now contracts. This dimensional cycling is what fatigues foundations.

July through September: monsoon

Intense, short, high-volume storms. An inch of rain in forty minutes onto ground that has been baked hard for two months produces runoff, not absorption. Water sheets across the surface and finds the same low spots.

Twice a year, then, your foundation soil goes from saturated to dry. Not once, like a temperate climate. Twice.

The things we look at, in the order we look at them

1. Grade

Six inches of fall in the first ten feet, away from the house, in every direction. This is where the majority of Flagstaff drainage problems live. Over the years, soil settles, landscaping gets added, gravel gets replenished, and the grade quietly reverses. It is fixable with a shovel and a wheelbarrow far more often than people expect.

2. Downspouts

A roof of ordinary size sheds thousands of gallons a year, and every downspout concentrates a chunk of that into one spot. If it discharges within a few feet of the wall, that spot is being water-jetted several times a season. Extensions should run at least five to ten feet out, further on a slope facing the house.

3. Where the snow goes

Uniquely important here. A six-foot snow pile shoveled against the garage wall every December is a slow-release water bomb aimed at your footing. Same for roof snow sliding off and landing in the same trench along the drip line all winter.

4. Hardscape pitch

Patios, walkways, and driveway aprons that have settled back toward the house are collecting runoff and delivering it. This one often gets fixed with foam lifting rather than replacement.

5. Roof and gutter condition

At our snow loads, gutters take a beating and ice damming is a real phenomenon. A gutter that has pulled loose dumps water at the wall all winter.

6. Irrigation

Drip lines and sprinkler heads too close to the foundation keep the soil there wetter than the soil elsewhere. That differential is what moves footings.

7. Subsurface conditions

Where the lot slopes toward the house or a neighboring property drains onto yours, surface fixes may not be enough and a drain line, swale, or dry well makes sense.

What we install, from cheapest to most involved

Regrading and downspout extensions

The first thing, almost always. It is inexpensive and it solves a surprising share of problems outright.

Swales and surface drains

A shaped channel or a trench drain that intercepts runoff before it reaches the foundation. On sloped Flagstaff lots this is often the difference-maker, because the water is arriving from uphill and there is no amount of grading right at the wall that will stop it.

Exterior footing drain

Perforated pipe in washed aggregate with filter fabric, laid alongside the footing and daylighted or routed to a dry well. In cinder soil, filter fabric selection and bedding detail really matter, because cinder produces fines that will silt up a poorly built drain within a few years.

Exterior waterproofing membrane

Applied to the outside face of the foundation wall while the trench is open. This is the thorough approach and the expensive one, since it requires excavating the perimeter. When we are already digging for underpinning, this is the moment to do it, because the trench is the cost.

Interior drainage and sump

For crawlspaces and below-grade spaces where exterior work is impractical. Perimeter drain inside the footing, routed to a sump pump. Combined with a sealed vapor barrier over the crawlspace floor, this is what turns a damp Flagstaff crawlspace into a dry one.

Crawlspace vapor barrier

Heavy polyethylene, lapped and sealed, run up the stem walls. Cheap, and it does more for the framing above than almost anything else on this list.

Freeze protection matters here

Anything that carries water outdoors in Flagstaff has to survive winter. Discharge lines that hold water freeze and burst, or freeze at the outlet and back the system up at exactly the moment it is needed. Drain lines need positive fall so they self-drain, discharge points need to stay clear of snow, and buried lines need to be below or protected against the 30-inch frost depth. Systems designed by someone used to working at 1,200 feet routinely fail here for exactly this reason.

What happens if you skip it

Water is the input to almost every other foundation failure mode. It washes cinder out from under footings, saturates clay so it swells, adds hydrostatic pressure against walls, rots crawlspace framing, and turns a small void into a large one. Everything else we repair costs more than drainage does. A homeowner who spends a few hundred dollars on grading and downspouts in September and skips the five-figure repair three years later has made the best trade available in this business.

Rules and permits

Grading and drainage work can require permits depending on scope and location, and there are stormwater rules about where you may discharge — you generally cannot solve your problem by routing water onto a neighbor's property. Inside city limits, the City of Flagstaff handles permitting and has its own stormwater program; unincorporated Coconino County handles the rest. Arizona licenses excavation, grading, concrete, and plumbing as separate contractor classifications through the Registrar of Contractors, and you can verify any license free at roc.az.gov.

Related repairs

• Sump Pump Installation
• Foundation Crack Repair
• Bowing Wall Repair
• Pier and Beam Repair
• Sinking Foundation Repair
• Slab Foundation Leveling

Questions about foundation waterproofing