Larkspur Equipment Pads

Nobody calls a concrete contractor about an equipment pad in July. The calls come in February, after a night when the power went out, the standby generator tried to start on a pad that had heaved out from under its mounts, and the flexible fuel line learned how much movement it could tolerate. That's when a small square of concrete stops being trivial.

Out here that machine is often the whole system. Well pump, propane tank, standby generator, heat pump, pressure tank in a small well house. On a Sage Port or Bear Dance property, losing one in a storm isn't an inconvenience, it's the day. So we build for the worst week of the year, not the average one.

Details we pin down before the pad gets formed

• Equipment submittal with footprint, weight, and the manufacturer's mounting pattern
• Required clearances on all sides, including whatever the service tech needs to open
• Conduit, gas line, and drain routing, with stub-up locations marked on the form
• Height above finish grade, set for local snow depth and roof shedding, not the minimum
• Whether the pad touches the building or stands free of it
• Access for the installer's equipment on delivery day, and the date it lands

Ten below, and the generator has to start

Cold is not what breaks these pads. Water is, and cold is what turns water into a jack. A pad poured on a thin scrape of dirt with no compacted base under it will take on moisture through fall, freeze, and lift, and it rarely lifts evenly. One corner comes up. The machine goes out of level. Isolators load unevenly, conduit bends past its radius, and a fuel or refrigerant connection takes stress nobody designed it for.

The prevention list is short and boring. Strip organics, lay a compacted free-draining base thick enough to matter, keep the pad top well above grade so meltwater leaves instead of pooling, and pitch the surface so what does land drains off. On small pads under unheated equipment we'd rather build a thicker base than a thicker slab. Frost doesn't care how much concrete is up top.

Winter stress, by what's standing on the pad

Vibration, conduit, and everything cast into the concrete

A machine that shakes will find any weakness you left it. Reinforcement matters more here than thickness does, because bar keeps a cracked pad acting as one piece instead of two. We keep steel mid-section, tie it rather than tossing it in, and detail anchors as part of the pour instead of drilling them afterward. Drilled anchors work; cast anchors work better and don't punch a hole for water to find.

Conduit and stub-ups go in before concrete, always, coordinated with your electrician. Coring a live pad later is a bad afternoon for everyone. And if the equipment sits against the house, we separate pad from building with an isolation joint so vibration stays out of the structure and the two can move on their own. Bonded together, a heaving pad drags the foundation into the argument.

Pouring pads in the shoulder seasons

Most of these jobs are small, which means they slot into a schedule easily and we can usually beat an installer's date. September and October are the busiest months for this work, for obvious reasons: people think about the generator right after the first cold snap. Spring is the other rush, when a winter of heaving has convinced somebody the old pad is finished.

We pour through the cold with heated mix, accelerator, and blankets, and small placements protect easily because there's little surface to cover. What we won't do is set one on frozen ground. Frozen base thaws in spring and your new pad follows it down. Better to support the equipment temporarily and pour the real pad when the ground is honest.

Half the tilted pads we replace were fine concrete. Somebody poured four inches on scraped dirt because the install was Friday. Two winters later the machine sits on a ramp, and we're pulling gas line and conduit to fix a job that needed one extra day the first time.The crew lead's read on it