Office Building Radon Mitigation, Los Angeles

Building Pressurization First

The physics is the same as sub-slab depressurization, run in the other direction. Instead of making the ground negative, you make the building positive. Increase outdoor air, adjust return balance, verify with a micromanometer across the floor slab, and the pressure differential that was pulling soil gas in reverses.

When it works, it is elegant and cheap: a controls adjustment and a balancing report rather than a construction project. When it does not, it is usually because the air handler has no spare capacity, the building is leaky at the top and stack effect overwhelms the adjustment, or the tenant will not tolerate the energy cost. In Los Angeles, where we are not conditioning outdoor air against a hard winter, the energy penalty is smaller than it would be in most of the country, which tilts more buildings toward this solution than you would expect.

Subterranean Parking Changes Everything

Most mid-rise LA office buildings sit on one to four levels of subterranean parking, and that is good news. The occupied space is no longer in contact with the ground; the garage is. A garage that is ventilated per code for carbon monoxide is usually already exchanging enough air to keep radon concentrations negligible, and the slab between the garage ceiling and the first office floor is a second barrier.

Where problems show up is at the connections: elevator shafts, stair pressurization systems, and the electrical and plumbing risers that run from the garage straight into occupied floors. Those are pathways. If a first-floor suite tests elevated in a building over parking, that is where we look first, and the fix is usually sealing and shaft pressure management rather than sub-slab work.

When Sub-Slab Is Still the Answer

Single-story and two-story office buildings on grade, common all over the Valley and the South Bay, get treated like any other slab building: diagnostics, suction points, pipe, fan, verification. In these buildings we route pipe through mechanical rooms and janitor closets and put fans on the roof, so the only thing a tenant ever sees is a manometer on a wall by the electrical panel.

Medical office is its own subcategory. Imaging suites, labs, and procedure rooms have their own air pressure requirements that have nothing to do with radon and everything to do with infection control, and those requirements win. We coordinate with whoever balanced the building before touching anything.

The Lease Question

Increasingly the reason an office landlord calls us is not a lender. It is a tenant. Corporate EHS groups, particularly at technology and life-science tenants, have started asking for indoor air quality data as part of lease negotiations and renewals, and radon appears on those checklists more than it did five years ago.

A landlord with a current, clean radon report answers that question in one email. A landlord without one spends three weeks scrambling during a renewal negotiation, which is the worst possible time to discover an elevated result.

Cost

Testing a floor plate typically runs $700 to $2,200. An HVAC-based solution, where it works, might be $1,500 to $6,000 including balancing and verification testing. Sub-slab systems on a single-story office building run $6,500 to $15,000. Multi-tenant buildings requiring after-hours work sit at the top of those bands.

Questions About This Service

Does an office building over subterranean parking need radon mitigation?

Rarely. The parking level takes the ground contact and its code-required ventilation typically keeps concentrations low, and the slab above adds a second barrier. When a suite in such a building does test elevated, the pathway is almost always a shaft or riser penetration rather than the floor, and the fix is sealing and shaft pressure management.

Can HVAC changes alone fix a radon problem?

Sometimes, and in Los Angeles more often than in colder climates because the energy penalty of extra outdoor air is smaller here. It requires an air handler with spare capacity and verification by measurement, not assumption. When it works you avoid construction entirely.

Will tenants notice the work?

In an HVAC-based solution, no, beyond a balancing crew in the mechanical room. In a sub-slab install, they will hear core drilling for about twenty minutes per point, which is why we do it before 7am or on weekends in multi-tenant buildings.

Our tenant is asking for indoor air quality data. What do we give them?

A current radon measurement report covering ground-contact occupied space, signed by a CDPH-listed professional, plus the mitigation and verification documentation if any exists. That is what corporate EHS reviewers are looking for, and having it ready shortens a renewal conversation considerably.

How much does office building radon mitigation cost?

$6,500 to $15,000 for a sub-slab system on a single-story office building. HVAC-based solutions, where viable, run $1,500 to $6,000 including balancing and verification.