24H Mold Inspection of Fontana

Downtown grew from A.B. Miller's town site, christened Fontana on June 7, 1913 when the old name Rosena was retired, and the 2,000 acres of citrus he planted were billed as the largest single citrus grove in the world. The blocks around Sierra Avenue and Arrow Boulevard hold the city's oldest housing — pre-war cottages and 1940s homes, some on raised foundations — and its older commercial frontage. Original galvanized plumbing, roofs layered over earlier roofs, and additions joined to small original houses are the recurring moisture paths here, along with flat-roofed storefronts whose drains clog with wind-blown debris.

Henry J. Kaiser fired up his steel mill on December 30, 1942, and for four decades it was one of only two steel mills west of the Mississippi before it closed in 1983. The roughly 2,000-acre site has since been remediated in sections under state oversight — the speedway built on its former coke-oven area ran its last NASCAR race in February 2023 — and much of the land has gone to logistics. Soil and groundwater cleanup is a separate field from mold, but the warehouse belt that replaced the mill carries its own moisture pattern: big low-slope roofs, clogged internal drains, and slab moisture working into stored goods.

The mill's workforce drove Fontana's postwar building boom, and the 50-bed hospital Kaiser opened in 1943 for steelworkers and their families became a seed of Kaiser Permanente. The single-story homes that went up as that workforce grew through the 1950s and 1960s fill much of the older city: stucco over wood frame on concrete slabs, with copper or galvanized lines, early forced air or wall furnaces, and plenty of evaporative coolers on the roof. Sixty-plus years later, slab leaks, failing drain lines, coolers leaking at their roof curbs, and garage conversions built straight onto the slab are the most common sources of hidden moisture on these blocks.

In the city's northern reaches, vineyards and open fan land gave way from the 1990s onward to master-planned neighborhoods such as Hunter's Ridge, Summit Heights, and Sierra Lakes, built on graded pads climbing toward the San Gabriel Mountains. This is also the part of Fontana most exposed to the strong wind events that funnel out of the mountain passes, lifting roof tiles and driving dust into vents and valleys. The homes are newer and tighter — two-story stucco over slab, attic HVAC, tile roofs — so the moisture risks are trapped interior humidity, condensation in attic ducts through long hot summers, and wind-damaged roofs that leak at the next storm.

On the southern edge of the city, Southridge Village was planned in the early 1980s into the slopes of the Jurupa Hills, a granitic ridge rising above the valley floor. Homes here sit on cut-and-fill pads with retaining walls and terraced yards, and the hard granite and decomposed-granite soil sheds rainwater quickly downhill rather than absorbing it. That concentrates runoff against uphill walls, onto lower lots, and into the joint between slab and foundation on homes cut into the grade. Clogged terrace drains and V-ditches, irrigation on steep yards, and older pool installations on sloped lots are the usual drivers of moisture problems in these neighborhoods.