What Contractors Need to Know About Methane Gas Vapor Mitigation Construction Bids
Methane Gas Vapor Mitigation Construction is a specialty field with minimal certified contractors available relative to other construction trades. This creates specific challenges and opportunities for contractors entering the bidding process.
Understanding the Certification Landscape
The limited number of certified methane mitigation contractors is an intentional result of the methane vapor barrier manufacturer’s selective certification process. To implement quality control measures, methane membrane manufacturers only certify a select number of contractors within regions to install their product.
This selective approach is necessary due to the detail-oriented nature associated with the installation of methane mitigation systems. Historically, vapor barrier manufacturers find an open-source installation approach leads to a wide variety of failure modes of Methane Vapor Mitigation Barriers.
Although limiting the number of certified installers is beneficial for material manufacturer’s quality control, it often puts general contractors, owners, and real estate investors in a vulnerable situation in which they are overseeing the construction of a process that they do not understand. It is important for an owner and general contractor to understand the methane mitigation system, the local building requirements, and the scope of work that a methane mitigation contractor is offering within their bid.
What General Contractors Should Review on a Methane Gas Control System Bid
There are several questions General Contractors should ask when reviewing a methane construction bid. Verifying this information will ensure the bidding process of your Methane Mitigation Construction system is conducted with efficiency and accuracy.
Material Specifications and Plan Compliance
The proposed material that is being used should be noted on the construction bid and match the corresponding specifications on the Methane Mitigation System plans. Often, Gas Mitigation Contractors will make substitutions for lower cost materials that are not equivalent. If this happens, you could end up with issues during the inspection of your Methane Mitigation system. Ultimately, the inspector can require you to implement the methane barrier that is specified on the plans, resulting in significant Change Orders.
When reviewing material specifications in bids, contractors should verify:
- The specific product name and model number
- Manufacturer certification documentation
- Compliance with LADBS or DTSC requirements
- Material warranty coverage and duration
- Installation temperature and weather requirements
Material substitutions must go through the engineer of record for approval before bidding. Proposing unapproved substitutions creates risk for both the specialty contractor and the general contractor managing the project.
Defining the Scope of Work Between Trades
Another important reviewing point is the scope that is being covered by the Vapor Mitigation Builder. Some aspects of methane mitigation construction overlap with concrete scope of work—this includes gravel or sand blanket and the Visqueen layer. There are also some aspects of methane mitigation construction that will overlap with your plumber and your electrician.
Common Scope Overlaps to Address in Bids
Some Mitigation Contractors will include this overlapping work in their bid while others will have this scope excluded. It is important to review the proposed scope of all bids and ensure that you are fairly comparing the bids and accurately representing the Methane Mitigation Design specifications.
Scope items that frequently cause confusion:
Concrete-Related Work:
- Base material preparation (gravel or sand)
- Vapor retarder (Visqueen) installation
- Coordination of pour schedules
- Protection of installed barriers during concrete placement
Plumbing Coordination:
- Penetration sealing for drain lines
- Scheduling around rough plumbing installation
- Sealing requirements for pipe sleeves through barriers
Electrical Coordination:
- Conduit penetration sealing
- Active system wiring and controls
- Fan electrical connections
- Sensor installation and wiring
General contractors should create detailed scope matrices showing which trade is responsible for each element. This prevents gaps in coverage and eliminates duplicate charges. Clear scope definition protects all parties and reduces change order disputes during construction.
Reviewing the Mobilization Schedule
The mobilization schedule requires thorough review to characterize how the Gas Mitigation Contractor has plans to execute the construction. This is a very good representation of how the contractor plans to execute the construction project. It also allows you to verify that all the scope of work is covered and comparable amongst the three bids that you received.
Why Detailed Mobilization Schedules Matter
Every job is different and requires a different mobilization schedule depending on the scope and how the construction will be organized. Ensuring that this is done accurately is important and requires a significant amount of detail. Unfortunately, methane mitigation contractors often do not want to put the time and effort into the sequence of events during construction, but this is a key component to preparing an accurate Mobilization Schedule.
Some Vapor Barrier Products are designed as a fluid spray-applied membrane that requires a pump for installation. With these products, the mobilization fees can be high, leading to large Change Orders in the event that unaccounted-for mobilizations are required.
Key elements contractors should include in mobilization schedules:
- Equipment delivery and setup timeline
- Crew size and specialized labor requirements
- Weather-dependent activities and contingency days
- Coordination points with other trades
- Inspection hold points and required lead times
- Material delivery schedules and staging requirements
- Demobilization and cleanup timeline
Spray-applied systems require additional mobilization considerations. The pumping equipment is expensive to transport and set up. If the contractor needs to return to the site for additional work due to poor coordination, the remobilization costs can be substantial. General contractors should ensure the schedule accounts for all necessary mobilizations upfront.
How Many Mitigation Construction Bids Should Contractors Solicit?
It’s best to get three Vapor Mitigation construction bids. This allows for a better understanding of what the cost is for a system on a low, high, and medium spectrum. By receiving three construction bids, you’re able to weed out bids that might be too low or too high. If a General Contractor were to only receive one construction bid, the possibility of inaccurate bidding is much higher, which can lead to budgeting issues during construction.
What the bid spread tells you:
Low Bid Considerations:
- May indicate missing scope items
- Could suggest inexperience with the specific system type
- Might reflect aggressive pricing to win work
- May not include required warranties or certifications
High Bid Considerations:
- Could indicate comprehensive scope coverage
- May reflect premium service and experience
- Might include enhanced warranties
- Could suggest risk premiums for unfamiliar work
Middle Bid Analysis:
- Often represents realistic market pricing
- Typically includes standard scope coverage
- Usually reflects experienced contractor pricing
- Generally balances cost and quality
General contractors should not automatically select the lowest bid. The middle bid often represents the most accurate pricing from contractors who understand the work and have priced it realistically. If all three bids are significantly different, it indicates scope interpretation issues that need resolution before award.
Evaluating Methane Gas Control Contractor Qualifications
According to the Contractor State License Board (CSLB), the best way to find a contractor is through referral. The Construction Industry’s bidding process has changed significantly with the use of internet search browsers like Google. General Contractors and Owners have the ability to receive “Cold Bids” from a variety of companies without actually knowing how the contractor performs the work and how the business is managed.
Although having the ability to receive bids from multiple companies easily is a huge benefit, receiving these cold bids could be a counterproductive action due to the uncertainty and unreliability of these leads. In the construction industry, word of mouth from your sphere of influence is still the best way to find a reliable Methane Vapor Mitigation Contractor.
Questions to ask when vetting specialty contractors:
- How many similar projects have you completed in the past year?
- Can you provide references from general contractors on similar projects?
- What manufacturer certifications do you currently hold?
- What is your typical crew size and project duration for this scope?
- How do you handle warranty claims and callback issues?
- What insurance coverage do you carry specific to methane work?
- Do you have experience with the specific building jurisdiction on this project?
Contractor licensing is just the starting point. General contractors should verify that specialty contractors hold current manufacturer certifications for the specific products specified in the design. These certifications often require renewal and continuing education, so contractors should request current documentation.
Expanding Scope: Waterproofing Capabilities
When receiving a construction bid from a specialized Methane Mitigation contractor, it’s important to realize that this contractor may also take on any necessary Waterproofing Project. This helps reduce costs and, in some cases, increase efficiency by increasing productivity and minimizing the required communication between different trades. This is because most Methane mitigation materials are also certified as Waterproofing materials.
Although this is true, not all Methane Mitigation contractors take on the responsibility of waterproofing. It is always essential to ask your contractor what their scope capabilities are.
Benefits of combined methane mitigation and waterproofing scope:
- Single point of responsibility for below-grade envelope
- Reduced coordination requirements between trades
- Streamlined scheduling with fewer mobilizations
- Consistent warranty coverage across related systems
- Better integration of penetration details
- Simplified inspection process
General contractors should evaluate whether combining these scopes makes sense for their specific project. On smaller projects, a single specialty contractor handling both systems often provides cost savings and schedule benefits. On larger projects, the scope may be substantial enough to warrant separate contracts with contractors specialized in each area.
Understanding Warranty Requirements
When receiving bids, another essential question is what the warranty periods for the Methane Mitigation system are. There are two types of warranties to acknowledge: one being the material warranty that the material manufacturer typically provides and the other being the labor warranty. To take advantage of these warranties, specific guidelines and processes must be met—processes required by both the Department of Building and Safety and the material manufacturer.
Material vs. Labor Warranties
Material Warranties typically cover:
- Product defects and manufacturing issues
- Membrane integrity and performance
- Chemical resistance and longevity
- Duration often ranges from 5 to 20 years
Labor Warranties typically cover:
- Installation workmanship defects
- Seam failures due to improper welding or adhesive application
- Penetration sealing failures
- Duration often ranges from 1 to 5 years
The sensitivity of Methane Mitigation Construction can easily lead to incorrect installations and failure of systems. If the proper inspections are not implemented, then it is possible for the material manufacturer and the contractor to not provide the associated warranty. This is not a good situation to have involvement in. It’s important to always budget the required inspections and processes related to Methane Mitigation.
Warranty requirements contractors must meet:
- Installation by manufacturer-certified applicators
- Compliance with manufacturer’s installation guidelines
- Third-party inspection at specified intervals
- Proper surface preparation and testing
- Documentation of installation conditions (temperature, humidity)
- As-built drawings showing barrier coverage and penetrations
- Photographic documentation of installation stages
Informing your team members of these processes is also necessary so that they will be fully aware that if these are not abided by, warranties will not be provided. General contractors should include inspection costs in their project budgets and coordinate these inspections with the specialty contractor’s schedule.
Managing the Learning Curve for General Contractors
Considering the youth of the Methane Mitigation industry, contractors are often not familiar with the entire process. As the owner is being offered a bid, it’s important to acknowledge your contractor’s willingness to learn and work with Methane Mitigation contractors to complete the systems. This will most likely be a learning process that the contractor must be open to and willing to take on.
Some contractors may charge additional fees for dealing with the scheduling and logistics of Methane Mitigation systems since they are not typically involved in a standard project. Be sure before construction begins that all parties are aware of the Methane Mitigation Construction Requirements as well as all associated work along with this.
How general contractors can prepare for methane mitigation projects:
Pre-Construction Preparation:
- Attend pre-bid meetings with specialty contractors
- Review the methane mitigation design with the engineer
- Understand the inspection sequence and hold points
- Identify coordination requirements with other trades
- Review jurisdiction-specific requirements
During Construction:
- Maintain close communication with specialty contractor
- Protect completed work from damage by other trades
- Coordinate concrete pour schedules carefully
- Document all installation stages photographically
- Attend all required inspections
Common Challenges to Anticipate:
- Weather-dependent installation windows
- Curing time requirements before covering
- Conflicts with other trade schedules
- Access requirements for equipment and materials
- Special staging and protection needs
General contractors new to methane mitigation should consider the first project a learning experience and build in schedule and budget contingencies accordingly. The specialty contractor should be viewed as a resource for understanding the process, not just another subcontractor to manage.
Preventing Common Oversights in Project Planning
It is an unfortunate occurrence that Methane mitigation requirements are missed on projects even if the building code requires them to be met. Often, this will come up at the final stage of the inspection process. If this occurs, it means that your architect, plan checker, and contractor are all unaware of the Methane Mitigation requirements for your area. This is an unfortunate occurrence that can be easily prevented.
How to Verify Methane Mitigation Requirements Early
This can be prevented by implementing the Methane Mitigation check, which can be executed using ZIMAS on all projects under construction within the Los Angeles area. If you are in the Los Angeles County Environmental Programs Division jurisdiction, the code requirements will be slightly different. You can check the website of the LA County Environmental Programs Division for information. If you are within Orange County, then you can check with their fire authority jurisdiction and their building department for your property’s Methane Mitigation Requirements.
Due diligence steps for contractors:
During Pre-Construction:
- Check ZIMAS or equivalent database during project feasibility
- Review Phase I and Phase II environmental reports if available
- Contact building department for specific requirements
- Identify methane zone classification for the property
- Review vapor intrusion screening levels if applicable
During Design:
- Ensure the design team includes methane mitigation if required
- Verify that plans include required details and specifications
- Confirm that plan check addresses methane requirements
- Review inspection requirements with building department
During Bidding:
- Include methane mitigation scope in bid documents
- Provide complete specifications to specialty contractors
- Allow adequate time for specialty contractor questions
- Conduct pre-bid meeting to review requirements
During Construction:
- Schedule inspections at required intervals
- Maintain required documentation
- Coordinate with building inspectors early
- Address any deficiencies immediately
Discovering methane mitigation requirements late in the project creates significant problems. Retrofitting systems after construction has progressed is expensive and disruptive. General contractors should make methane zone verification a standard part of their due diligence process on every project, regardless of project type or location.
Cost Management and Change Order Prevention
Methane mitigation construction presents specific risks for cost overruns and change orders. General contractors can protect themselves and their clients by addressing these risk areas during bidding and pre-construction.
Common sources of change orders:
Material Substitutions: When specified products are unavailable or the contractor proposes alternatives, engineering review and approval is required. This process takes time and may result in additional design fees.
Scope Gaps: Undefined responsibility for overlapping scope items leads to finger-pointing and added costs when work needs completion.
Inspection Failures: Work that doesn’t meet specifications requires removal and replacement. This is particularly costly with spray-applied membranes or installed barrier systems.
Schedule Delays: Weather delays, coordination issues, or inspection hold-ups can result in additional mobilization charges from the specialty contractor.
Unforeseen Conditions: Contamination levels different from initial testing or groundwater issues can require system upgrades.
Strategies to minimize change orders:
- Get complete clarification of scope boundaries before contract award
- Include allowances for likely additional work
- Build schedule float around weather-dependent activities
- Establish clear approval processes for material substitutions
- Maintain detailed documentation of site conditions
- Conduct thorough pre-construction meetings with all trades
General contractors should resist the temptation to award work based solely on low price. A slightly higher bid from an experienced contractor with a complete scope definition often results in lower final costs than a low bid with missing scope items.
Building Department Coordination
Different jurisdictions have varying requirements for methane mitigation systems. General contractors must understand the specific requirements for their project location.
Los Angeles Department of Building and Safety (LADBS):
- Requires methane testing per their specific protocols
- Has detailed standard plans for mitigation systems
- Requires deputy inspector sign-offs at specific stages
- Enforces strict compliance with methane code requirements
Los Angeles County Environmental Programs Division:
- Different testing protocols than LADBS
- May have different mitigation requirements
- Coordinates with LA County Public Works
- Reviews environmental documentation separately
Orange County Fire Authority:
- Handles vapor mitigation oversight in their jurisdiction
- May have different active system requirements
- Coordinates with local building departments
- Reviews fire safety aspects of active systems
Department of Toxic Substances Control (DTSC):
- Oversees vapor intrusion mitigation for contaminated sites
- Has specific screening levels and risk assessment protocols
- Requires vapor intrusion mitigation plans (VIMPs)
- May require long-term monitoring programs
General contractors should contact the appropriate jurisdiction early in the design process to understand specific requirements. Building relationships with plan checkers and inspectors familiar with methane mitigation can streamline the approval process.
Final Considerations for Contractors
Methane Gas Vapor Mitigation Construction requires specialized knowledge, careful coordination, and attention to detail. General contractors entering this market should:
- Invest time in understanding the technical requirements
- Build relationships with qualified specialty contractors
- Verify requirements early in every project
- Include adequate budget for inspections and testing
- Plan for the learning curve on initial projects
- Document everything thoroughly
- Maintain open communication with all parties
The limited number of certified installers creates opportunities for contractors willing to develop expertise in this field. As methane mitigation requirements expand to more jurisdictions, demand for qualified contractors will continue to grow.
General contractors who approach methane mitigation professionally—with proper planning, qualified subcontractors, and attention to detail—will find these projects manageable and profitable. Those who treat it as just another scope item without understanding the requirements will face costly surprises and client dissatisfaction.
The key to success is recognizing that methane mitigation is a specialty trade requiring respect for the technical requirements, coordination needs, and regulatory oversight that make these systems effective in protecting building occupants from subsurface contamination.