El Paso concrete that holds up to sun, wind and monsoon runoff

Desert ground: sand, caliche, fill and river clay

A slab is a stiff, thin plate, and it is only as steady as whatever it rests on. Around El Paso that support varies more than most people expect. Much of the city sits on sandy and gravelly desert soils, some of them washed down from the Franklin Mountains over a very long time. Mixed through them, at different depths, are layers of caliche, a natural cement of calcium carbonate that can be as hard as rock in one spot and chalky and broken a few feet away.

Concrete handles being squeezed very well but handles being bent poorly. When the ground under a driveway is uniform, a car rolls across it without trouble. When one corner sits on firm caliche and the other on loose sand, every load flexes the slab a little along the line where the support changes, and eventually it cracks there. Many of the diagonal cracks at patio corners and the cracks running parallel to garage doors around town began exactly this way.

Some dry desert soils have another habit. They are loose enough that they only keep their volume while they stay dry. The first time they are soaked, by a leaking irrigation line, an overflowing pool or a yard that flooded in a storm, the grains can slump into a tighter arrangement and the surface drops. A slab that was flat for years and then sinks in a single season is often sitting over a spot like that.

Down in the river valley, from the Upper Valley on the west side to Ysleta and Socorro on the east, the soils change to silt, fine sand and clay deposited by the Rio Grande. Clay swells when it takes on water and shrinks as it dries, and flood irrigation of yards and fields nearby can keep that cycle going through the year. Newer subdivisions on the east and west sides add a fourth condition: graded fill, which settles for years if it was not compacted well.

Heat, wind and the few storms that matter

El Paso earns its Sun City nickname. Long, hot summers, low humidity and strong sunlight shape how concrete should be poured and finished. Fresh concrete needs water to harden properly, and dry heat pulls that water from the surface quickly. If the top dries faster than the concrete below, shallow cracks can open within hours and the surface ends up weaker and dustier than it should be.

Spring adds wind. Gusty afternoons with blowing dust are common from late winter into spring, and wind is among the fastest ways to dry a fresh slab. That is why contractors in the region commonly pour at first light, set up windbreaks or use evaporation retarders on a breezy morning, and apply a curing compound or keep the surface damp once it is finished.

Rain is scarce for most of the year, but monsoon thunderstorms in summer can drop a lot of water quickly. Flat and low-slope roofs are common here and empty through canales, scuppers or downspouts, which concentrate that water onto small patches of ground. When one of those patches is the edge of a driveway or patio, the soil below gets soaked and dried repeatedly. On hillside lots near the mountains, runoff can also sheet across a driveway and into a garage in minutes.

Winter is milder than in colder regions, but hard freezes still happen, and the Mesilla Valley and the mesas can run a little colder at night. A freeze in the first days after a pour slows the concrete from gaining strength, so a contractor may cover the slab or move the date if the forecast turns cold.

Five questions that separate a lasting pour from a short-lived one

A brand-new slab tells you little about how it will look after five monsoon seasons. What decides that is mostly buried or finished before you ever see it, so raise these questions while the quote is still on paper.

What will the slab sit on?

A good plan removes topsoil, roots and loose fill, moistens and compacts the native soil, and places a layer of crushed rock or road base compacted in lifts. Where caliche is patchy, high spots may be broken out so the base is even. A quote that skips the ground entirely is quietly assuming the ground is perfect.

How thick, and where?

Driveways and patios for cars and foot traffic are commonly poured around four inches thick. Parking spots for a work truck, a trailer or a motorhome usually call for more, and edges often get thickened because they have less support than the middle.

Where will it crack?

All concrete shrinks as it cures and moves with the temperature, and the daily swing in the desert is large. Control joints give that movement straight, planned places to go. A widely used guideline sets their spacing, in feet, at roughly two or three times the slab depth in inches, with each cut reaching about a quarter of the way down.

Is the steel in the right place?

Reinforcing steel and mixed-in fibers keep the pieces on either side of a crack from spreading apart or shifting out of level. They do not prevent the crack, and steel that ends up pressed into the rock beneath the pour contributes almost nothing. Ask how it will be supported during the pour.

Where does the water go, and how will it cure?

The surface should pitch water toward the street, the yard or a drain, never toward the house or garage, and roof drains near the slab should be directed past it. On pour day, ask how the fresh surface will be protected from sun and wind, and how long it will be kept curing afterward.

Request an estimate visit

Send the property address and a sentence about the project: a new pour, a widening, a slab that has sunk or cracked, or a patio you want to enlarge. A reply comes back to set up a visit.

Six kinds of home concrete projects

Residential concrete falls into a handful of project types, and many jobs combine a few. A driveway widening often comes with a side-yard pad for a trailer. A new back patio may include steps from the door and footings for a shade cover. Stamped patterns, color mixed into the batch and exposed stone finishes can go on most of them, each with its own upkeep in strong sun. Repair and replacement is its own category, because the first step is working out why the old slab failed.

Details that make the first conversation useful

None of these is required, and rough answers are fine. They simply help the contractor arrive at the visit with the right questions.

• The street address, plus whether an HOA in your subdivision signs off on exterior projects.
• What you want built or fixed and its rough footprint. Counting your steps along each side works fine.
• What will use it: cars, a work truck, a trailer or motorhome, a hot tub, or just chairs and a table.
• What is there now, such as gravel, desert landscaping, old concrete or asphalt that has to come out.
• Where roof drains, coolers and irrigation lines sit near the area, and where water ran in the last storm.
• Whether the work area is behind a block wall or a narrow gate, since that affects how concrete reaches it.
• Any finish you have in mind: broom, stamped, colored, salt finish or exposed aggregate.

If the project touches the street, the curb or the sidewalk, ask the city or county that covers your address what approval is needed, and ask your HOA about its own review. On the New Mexico side, those offices are different from the Texas ones, so find out early.

How a project usually moves from request to pour

After a request arrives, the contractor schedules a walk-through. Standing on site is how the actual job gets defined: soil, slope, the roof drains and irrigation, any damage to an existing slab and what caused it, and how a truck or pump can reach the pour. Plenty of projects that seem straightforward on a phone screen reveal a drainage fix or deeper base work in person.

Next comes a written estimate. The useful ones itemize square footage and depth, digging and base, steel or fiber, joint spacing, surface finish, how water will leave the slab, how the concrete reaches the pour, and whether tearing out and hauling old material is covered. Put competing bids side by side on those lines, since a low number frequently leaves one of them out.

Should you move forward, the pour date is fitted to the forecast: dawn starts in the hottest months, wind watching in spring, and a freeze check in the cold months. Once it is placed, walking on the slab waits a few days and driving on it waits longer, and the contractor gives you both dates for that particular job.

Areas homeowners send requests from

Requests come from both sides of the Franklin Mountains and across the state line into New Mexico. Foothills lots, valley properties near the river and flat mesa subdivisions each bring their own soils, slopes and access, so the visit to the property tells a contractor more than a ZIP code ever could.

El Paso concrete questions, answered plainly