24H Mold Inspection of El Cajon

In 1876 Amaziah Knox opened a hotel near what is now the southwest corner of Main Street and Magnolia Avenue to serve travelers bound for the Julian gold fields, and the town that grew around it incorporated in 1912. Part of that hotel survives as the Knox House museum. Downtown's older commercial blocks along Main Street hold the city's oldest construction — masonry storefronts, flat roofs behind parapets, and apartments and offices above ground-floor shops — with mid-century homes on the surrounding streets. Parapet flashing, clogged roof drains, and old supply plumbing are the usual moisture sources, and in mixed-use buildings a leak upstairs becomes the shop's problem below.

Ed Fletcher laid out the Fletcher Hills subdivision in 1927 and 1928, and lots went on sale just as the Depression arrived, so much of the hillside stayed empty until the housing surge of the 1940s and 1950s. The neighborhood fills the hills on the city's west side, up to the mesa where Grossmont College bought its 135-acre campus site in the early 1960s. Homes here are mostly mid-century ranches on sloped lots, some on raised foundations over crawl spaces, others stepped into the grade. Slope runoff against uphill walls, original plumbing at or past its service life, and crawl spaces that stay damp through a wet winter are the defining risks.

Bostonia still carries the name Charles Crosby and William Souther brought with them when they came from Boston, Massachusetts in 1886. Today it is a dense mix of mid-century ranch homes, small apartment buildings, and mobile home parks along Broadway and the streets running north toward Pepper Drive. Manufactured homes have their own moisture profile — plumbing routed through an underbelly wrap that hides leaks, skirting that traps humidity beneath the floor, and roof seams and add-on porches that leak at the joints. In the older stucco houses, cracks and failed window flashing let rain into the wall assembly, where it stays long after the surface has dried.

Camp Gillespie opened in 1942 as a paratrooper training base on the valley floor, and after the war it became the civilian Gillespie Field airport, ringed today by industrial parks, hangars, and light manufacturing. This is the low ground of the valley, near the channelized course of Forester Creek, which drains the city northward toward the San Diego River and runs through concrete for much of its length. Flat-roofed industrial buildings with internal drains, hangars with large door openings, and slabs poured without vapor retarders define the moisture pattern here, along with storm runoff that collects on the flat valley floor after heavy rain.

The eastern side of the valley rises into Granite Hills, where homes sit among boulder-strewn granite slopes facing open hillside. In late September 1970 the Laguna Fire burned westward about 32 miles out of the mountains to the outskirts of El Cajon, destroying some 382 homes across the county. Many homes here are 1960s and 1970s ranch and custom houses on graded lots, with pools, retaining walls, and long driveways. Decomposed granite sheds water quickly, so storm runoff concentrates against uphill walls and slab edges, and terraced yards with heavy irrigation keep those walls damp well into the dry season.