Concrete Slabs in Tigard, OR

Concrete slabs are the plain workhorses of a property: the floor of a garage or shop, the pad under a shed, a parking spot for an RV or boat, and the base under a hot tub or heat pump. In Tigard, where Washington County's hazard plan notes that high ground water and seasonal flooding drive many of the county's drainage problems, a slab's life depends on what is under it. A pad poured on wet, soft soil will settle at the corners, rock and crack. A pad on a compacted rock base, at the right thickness, stays flat for decades.

Garage floors

HomeGuide's slab guide lists two-car garage floors, typically 20 by 20 to 24 by 24 feet, at 4 to 6 inches of reinforced concrete. Inside a garage we pay attention to the slope toward the door so water dripping off cars runs out, the joint with the driveway, and moisture coming up from below. A vapor barrier under the slab helps keep a garage, shop or finished space drier, and it is worth discussing for any floor that will hold stored items or be coated later.

Shed, shop and outbuilding pads

HomeGuide gives about 4 inches as typical for a shed foundation, often without reinforcement. Bigger shops, or buildings with heavy shelving, workbenches or vehicles inside, need more thickness, steel and thickened edges where the walls bear. We set the pad slightly above the surrounding grade so water flows away instead of pooling under the building's sill.

RV, boat and trailer pads

A motorhome or loaded trailer puts a lot of weight on a small area. HomeGuide's driveway guide recommends 5 to 6 inches for RVs and heavy vehicles. We add reinforcement, plan the approach so the rig can be backed on without dropping a wheel off the edge, and check the drive approach and side setbacks if the pad connects to the street. Under Tigard Municipal Code 15.10.020, residential approaches must sit at least 6 feet from the projected side property line, with limited exceptions.

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Hot tub and equipment pads

A filled hot tub can weigh several tons, and a pad that settles unevenly can stress the shell. HomeGuide's patio guide recommends 6 inches with added reinforcement under hot tubs and outdoor kitchens. Heat pump and generator pads are smaller but should sit level and above grade so water drains away from the equipment.

Permits and placement

Whether a slab or the structure on it needs a permit depends on what it is and where it sits on the lot. The City of Tigard notes that a building-permit exemption does not exempt a project from planning requirements, such as setbacks, and its Planning Division takes questions at 503-718-2421. We confirm the requirements for your address before we schedule.

Cure time

HomeGuide says a slab can usually take foot traffic after one to two days, vehicles after one to two weeks, and reaches full cure in 28 to 48 days. Wait before setting a heavy shed, a filled hot tub or a garage floor coating, and we will give you dates for each.