Radon Testing & Mitigation in Sherman Oaks

This Is Where LA's Radon Actually Is

Los Angeles County averages about 1% of buildings above the action level, and that number is doing a lot of hiding. The zip codes along the southern edge of the San Fernando Valley, where the Santa Monica Mountains meet the valley floor, are the exception, and the California Department of Public Health has explained why: the hills there contain marine sedimentary rock with higher than background levels of naturally occurring uranium, and material eroded from those hills makes up the soil at their base.

The state's testing database made this concrete. In the 91604 zip code covering Studio City, 20 of 134 tests came back elevated, and the state's annual report described area readings averaging around 20 pCi/L, five times California's action level. Elevated results have also shown up in Encino, Tarzana, Chatsworth, West Hills, and Woodland Hills. Meanwhile Valley Village at 91607, a couple of miles north on flat ground, produced 95 tests with essentially nothing.

Two miles apart, completely different answer. That is the case for testing rather than assuming.

The Commercial Stock Along Ventura Boulevard

Sherman Oaks commercial property is mostly the Ventura Boulevard corridor: two and three-story professional and medical office, retail with offices above, and a substantial inventory of older buildings converted to clinical and therapy practices. Many sit on the slope side of the boulevard with ground contact on multiple levels, and a fair number are on raised foundations.

North of the boulevard toward the Sepulveda Basin the ground flattens and the readings drop. We have tested buildings on opposite sides of Ventura and gotten meaningfully different numbers, which tells you how tight the geology is here.

Multifamily in the 91403 and 91423 Zips

Sherman Oaks has a dense inventory of 1960s and 70s apartment buildings, many on subterranean or tuck-under parking. Tuck-under parking is a useful feature for us: it takes the ground contact away from ground-floor units the way a full garage does. Buildings with slab-on-grade first-floor units, particularly on the slope side, are the ones we would want tested before a lender ever asks.

Honestly, this is the one submarket in Los Angeles County where we would suggest an owner test proactively rather than waiting for a transaction to force it. Elsewhere in the county the base rate is low enough that waiting is defensible. Here it is not.

Cost

Small commercial testing $650 to $1,800; multifamily $45 to $110 per unit. Mitigation on hillside buildings tends toward the upper end of our ranges, $9,000 to $18,000, because multi-level ground contact often means more than one system, and raised-foundation buildings need sub-membrane work at $12 to $22 per square foot of crawl space.

What To Do Now

Own or manage a ground-contact commercial or apartment building south of Ventura Boulevard? Test it. It costs very little, most results come back fine, and this is the part of the county where the ones that do not come back fine are actually meaningful.

Related: radon levels around Los Angeles and commercial mitigation systems.

Sherman Oaks Questions

Why is radon higher in Sherman Oaks and Studio City than the rest of LA?

Because of the rock in the hills along the southern edge of the San Fernando Valley. The California Department of Public Health has attributed elevated readings in those zip codes to marine sedimentary rock containing above-background levels of naturally occurring uranium, with soil at the base of those hills derived from that material. Zip codes farther north on flat valley ground, like Valley Village, test very low by comparison.

How high have readings actually been?

In the state's own radon database, the 91604 zip code covering Studio City produced 20 elevated results out of 134 tests, with the state's annual report describing area readings averaging around 20 pCi/L, five times California's 4.0 action level. That is an unusual result for Southern California and it is why this pocket gets treated differently.

Should we test proactively even without a lender asking?

In this submarket, yes. Countywide the base rate of elevated results is low enough that waiting for a transaction to trigger testing is defensible. On the slope side of Ventura Boulevard it is not, and the cost of finding out is small.