Newest Methane Testing Code for Accessory Dwelling Units

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Do I need an LADBS Methane Test for my ADU?

The latest California building code updates have increased the eligibility for single-family dwellings to build an accessory dwelling unit (ADU) within their Single-Family Dwelling Property line. If the subject property is located within LADBS’ Methane Zone, the Methane Testing and Methane Mitigation Construction will be required.

The updated ADU Building Code has California residents scrambling to hire contractors and refinance their homes to build these accessory dwelling units to increase income for houses. Some homeowners who have zero experience in construction have their homes turned into construction sites. The construction of accessory dwelling units disrupts the comfort of homes and financially impact homes through the refinancing process. Due to this, the budget concerns for the construction of accessory dwelling units typically have low budgets to ensure that there is a proper profit margin present.

Homeowners need to hire an Architect to design the accessory dwelling unit; standard structural plans can save on engineering costs. Come time for construction; the owner does have the option of doing a home build as an owner-builder, which allows the homeowner to act as a contractor for the project. Owner-builder construction will save on construction costs by not hiring a general contractor to build the project. Although this will save on construction costs, the requirement of managing the subcontractors is significant and time-consuming, so often, it is not an option for homeowners.

During the design phase of the accessory dwelling units, an experienced Architect will check with Sway Features to establish whether the property is located within the LADBS Methane Zone. Verifying the Methane hazard classification is recommended for all projects that require new construction within the Los Angeles department of building and safety. 

Suppose it is concluded that the accessory dwelling unit is being built within the LADBS Methane Zone. In that case, the project will require a Methane Test, Methane Mitigation Design, and Methane Mitigation Construction. Neighboring Building jurisdictions also have Methane Gas Intrusion Code requirements.

New LADBS Methane Testing and Mitigation Exceptions for ADUs

The LADBS Accessory Dwelling Unit (ADU) Methane Mitigation process consists of three parts Methane Test, Methane mitigation design, and Methane Mitigation Construction. 

The Los Angeles Department of building and safety is aware of the budget restrictions for single-family dwelling construction and accessory dwelling units. Due to budget concerns, LADBS has granted accessory dwelling unit methane mitigation exceptions. Below is a summary of each applicable Exceptions.

  1. Standalone methane gas detectors with battery-back can be used instead of the commercial-grade alarm and gas detection system. 
  2. 6-mil thick Visqueen may be used instead of an impervious membrane.
  3. A more robustly designed sub-slab methane ventilation system may be implemented in place of the 1st level methane mechanical ventilation system and the below-grade methane extraction system.

Applying the above-listed Methane Mitigation LADBS Code exceptions is a great way to save on the methane mitigation construction costs.

Do I have to conduct a Methane Test for LADBS?

Another option that could be possible for the use of Methane Mitigation Construction of an accessory dwelling unit is passing on a methane test. Per the Methane Mitigation Construction code, it’s not technically possible to entirely disregard the results of a methane test, but there is the option of assuming the worst-case scenario; a level five methane mitigation system. 

What are the repercussions of assuming a level five methane mitigation system for an accessory dwelling unit? To evaluate this scenario, both time and money need to be considered. From a time perspective, forgoing the level 5 methane hazard classification is beneficial because a Methane test no longer needs to be conducted, which can take up to two weeks of testing time and analysis. From a cost perspective, the implications are that we will need to implement the accessory dwelling unit exceptions by applying the requirement of the active Methane mitigation components. Based on the LADBS methane Mitigation Code exceptions of Single-Family Dwellings and their accessory’s, Level 5 Methane Mitigation systems can lead to the use of standalone Methane detectors. In comparison to testing with a level 1 or 2 Methane Mitigation system, the cost of the es standalone detector and the more robust sub-slab ventilation system will depend on the architectural design approach. A Methane mitigation cost analysis for Accessory Dwelling Units needs to be implemented to confidently establish the most cost-effective methane hazard mitigation approach for Accessory Dwelling Units.

When building an accessory dwelling, there are advantages of conducting a Methane test for LADBS. An LADBS Methane Testing Laboratory must perform the Methane Test. If the Methane Soil Gas Test’s Certificate of Compliance reports a Level 1 or 2, the methane mitigation requirements will significantly reduce the cost of methane mitigation construction.

The LADBS Methane Mitigation Exceptions drive the cost reductions for Single Family Dwellings and their Accessory Dwellings Units. Specifically, for the low-level methane Hazards levels, a Visqueen layer can be implemented instead of the methane barrier. Visqueen can save on material costs for as much as 20 times compared to the methane barrier material costs.

New Methane Testing Code – LADBS Garage conversion to an ADU 

Homeowners in the Los Angeles area have been contemplating the new California code, which allows them to have an Accessory Dwelling Unit and a Junior Accessory Dwelling Unit to their single-family dwelling property. Many single-family dwellings in Los Angeles have detached garages that re-occupying space on the property at a net negative return on investment. The new California building code allows homeowners to convert the Garages to an ADU. By converting a garage into an ADU or JDU, the following benefits can be taken:

  • Maintain position of a structure relative to property lines

The LADBS Building code will require new construction to be situated 4 feet from the property line; if an existing garage is converted, the existing structure can be used, likely positioned on the property line based on historical building codes. 

Depending on the application, up to 100 SqFt of Space can be gained on the ADU, which, based on the current rates, can increase property value by $60,000.

  • Save costs on Framing and Foundation

Existing garages have the footings and framing already built and ready for reuse! Often some upgrades may be necessary based on the age of the structure, but the costs o of upgrading the existing foundation and framing is less than the material costs of building from scratch.

  • Save on LADBS Methane Testing and Methane Mitigation Construction

The LADBS Methane Mitigation Code will require a Methane Test, Mitigation Design, and Methane Mitigation Construction for all new construction located within the Methane Zone. 

The costs associated with the Methane Vapor Mitigation system should be budgeted early on to ensure they are considered. However, the LADBS Building code does have some expectations that may be granted for the conversion of garage to ADUs. To provide an accurate and best approach for LADBS Methane Testing and Methane Mitigation for a garage to ADU Conversions, its best to contact a methane mitigation consultant to review project-specific scope and corresponding methane mitigation requirements. Generally, there are several Methane Testing and Methane Mitigation options:

Install the Methane Sub Slab Vent System and Methane Impervious membrane only in the new scope where a new concrete slab will be poured.

Add retrofit methane barrier coating on the existing concrete slab to mitigate the migration of methane gas or vapor intrusion.

– Apply exception that will result in an exemption of mitigation requirements for the project. This exception will be applied towards the LADBS Methane Testing requirements. LADBS will enforce the Methane Mitigation Construction based on pouring a new slab or foundation for the project. If an existing slab on grade or footings is used, the code requirements will not require a Methane Test or implement the Methane Mitigation System. Any addition to a single-family dwelling or accessory dwelling unit addition will require a Methane Mitigation System for single-family dwellings, accessory dwellings, or commercial buildings.

Do I need a Methane Test for an Addition to a Single-Family Dwelling?

Based on the LADBS methane mitigation code requirements for additions Buildings, the LADBS code will require a Methane mitigation System, including conducting Methane Tests on any size of an addition. Conducting technical analysis of the LADBS Methane Code implies that a 5 SqFt addition to an existing 5,000 SqFt building will need Methane Mitigation Conduction. This issue in the code was caught early on, so an LADBS issued Bulletin P/BC 2014-102 titled “Methane Hazard Mitigation Standard Plan: Simplified Method For Small Additions” to address this issue. The Simplified Method for Small Additions bulletin was published to allow Methane Testing and Methane Construction exceptions for additions to any structure. These expectations may lead to eliminating the Methane Mitigation requirements or outlining cost-effective and reasonable mitigation approaches for the small additions to a structure. 

Raised floor foundations in themselves or methane mitigation features, so conducting an LADBS Methane Test may not be required. There are unlimited variables when analyzing methane testing and methane mitigation construction requirements for a project; it’s best to consult with a methane mitigation consultant to evaluate what is or isn’t required for the LADBS code for the specific project.

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