Do You Need As-Built Drawings for a Tankless Water Heater?

If you are planning to replace a storage water heater with a tankless unit, one of the first questions is usually whether the city will require plans. The short answer is: sometimes a simple tankless water heater permit is enough, and sometimes the scope grows into a permit set that benefits from as-built drawings or existing conditions plans. In California, that answer often depends on what is changing beyond the appliance itself—gas piping, venting, wall penetration, electrical service, mounting location, seismic details, combustion air, or alterations to the space around the unit.

For many homeowners, contractors, and small property managers, the challenge is not the water heater. It is documenting the existing house accurately enough for permit review and installation. FastAsBuilt provides field-measured as-built drawings and measured floor plans across California, with local crews serving Southern California, the Bay Area, and San Diego. We measure on site with laser tools, and senior drafters turn those measurements into permit-ready CAD files in PDF and DWG format, which can be useful when your tankless project needs more than a basic equipment swap.

When a tankless water heater permit is simple—and when it is not

A like-for-like replacement in the same location may be fairly straightforward if the new unit fits the code requirements for gas, venting, drainage, clearances, and access. In some jurisdictions, that can mean a relatively simple permit process with manufacturer information and basic installation details. But many tankless upgrades are not truly like-for-like.

A project can become more involved when you:

• Move the unit to a new wall, closet, garage, exterior location, or utility area
• Upgrade or reroute gas piping because the tankless unit has higher demand
• Add or modify venting, especially through walls or roofs
• Add a new electrical circuit, disconnect, or outlet
• Convert from interior to exterior installation, or vice versa
• Work in a condo, multifamily building, historic property, or commercial space
• Combine the project with remodeling work such as a garage conversion, ADU, or kitchen remodel

Once the project includes building, mechanical, plumbing, electrical, or fire-life-safety questions beyond the appliance cut sheet, accurate existing conditions become much more important. That is where as-built drawings can save time and reduce back-and-forth during plan check.

Do you always need as-built drawings for a tankless water heater?

No. You do not always need as-built drawings just to get a tankless water heater permit. Many jurisdictions can issue over-the-counter permits for limited scope work, especially when a licensed contractor is replacing a unit in place with no major reconfiguration. But if the city asks for floor plans, elevations, utility routing, or location-specific notes, as-built drawings become very helpful—and in some cases effectively necessary.

Think of as-built drawings as the factual base layer of the permit package. They show what is there now: room layout, wall locations, doors, windows, utility locations, dimensions, and the installed conditions that designers and contractors have to work from. If you are not sure what they are, this overview of what as-built drawings are gives the basic concept.

For a tankless project, the city may not use the term “as-built drawings.” Staff might instead ask for:

• Existing conditions plans
• A floor plan showing the current water heater location
• An exterior elevation with the proposed vent or unit placement
• A site or utility plan if gas service changes are involved
• Sections or details for wall penetrations, mounting, or enclosures

Those requests are common when the installation interacts with the building envelope, structure, or utility systems in a visible way.

Why existing conditions plans matter for permit review

Permit reviewers are trying to answer practical questions. Where is the unit located? Is the new equipment inside conditioned space, in a garage, on an exterior wall, or in a closet? How far is it from openings, property lines, ignition sources, and circulation paths? Will the work affect egress, accessibility, weather protection, or fire-resistance requirements? Does the gas line route make sense? Is there room for service access?

Without a measured drawing of the existing house or building, those questions often get answered with rough sketches that leave out dimensions or conflict with field conditions. That can slow down approvals and create change orders later. Clear existing conditions plans help everyone see the same starting point.

They are especially useful when the tankless unit is part of broader permitted work. If you are already preparing plans for a larger project, a measured base drawing can support multiple scopes at once. Related permit situations come up often in projects like planning before a renovation or when assembling the drawings needed for a California building permit.

Common California scenarios where as-built drawings help

In California, local jurisdictions vary, but several recurring situations make measured plans valuable for a tankless water heater permit.

Garage and utility room installations

Garages often involve clearance, ignition source, bollard or vehicle impact concerns, and interactions with conversion work. If the garage is being remodeled, legalized, or partially converted, documenting the existing layout is important.

Exterior wall installations

Exterior tankless units can trigger questions about mounting height, weather exposure, venting, clearances to openings, and visibility from public or shared areas. An exterior elevation and measured wall location can help address those items clearly.

Closet or interior replacements

When a tankless unit is installed in a closet or small mechanical space, the city may want to see access, combustion or venting approach, drainage, and any framing or finish changes.

Condo and multifamily work

Attached housing often has tighter rules around common walls, penetrations, exterior appearance, and HOA review. Existing conditions plans can help distinguish private-unit work from common-area impacts.

Historic or older homes

Older California homes may have undocumented prior work, unusual wall thicknesses, tight utility chases, or limited gas capacity. Measured drawings help avoid assumptions. If a property has historic considerations, confirm local review requirements and any Mills Act implications directly with the jurisdiction before finalizing plans.

These are not edge cases. They are normal conditions that can turn a “simple” appliance replacement into a small but real permit coordination exercise.

What as-built drawings for a tankless project usually show

For a tankless water heater permit, the exact drawing set depends on scope, but useful as-built drawings often include a concise record of the spaces and surfaces affected by the installation. The goal is not to create a giant plan set if the project is small. The goal is to show the existing building clearly enough that the proposed work can be reviewed accurately.

• Measured floor plan of the room, garage, exterior wall zone, or unit area
• Location of existing water heater, doors, windows, cabinets, fixtures, and appliances
• Wall lengths, ceiling heights, and key clearances
• Exterior elevations where the unit or vent termination will be visible
• Basic sections when vertical relationships or penetrations matter
• Notes identifying existing gas, water, vent, drain, or electrical connection points where visible and relevant

If your designer or contractor is preparing the proposed plan, they can use the measured drawing as a reliable underlay. That reduces redlines caused by mismatched dimensions or guessed wall locations.

FastAsBuilt’s process is built for this kind of permit support: on-site laser measurement followed by senior drafters producing permit-ready CAD files in PDF and DWG. For many homeowners, that is the easiest way to move from “we think the unit will fit here” to a coordinated drawing package.

How tankless water heater upgrades can expand into bigger permit scopes

One reason people underestimate documentation needs is that tankless installations often connect to larger building decisions. A new unit may be part of a remodel, an ADU, a home addition, or a strategy to free up floor area where the old tank sat. Once that happens, existing conditions plans become much more valuable.

Examples include:

• Removing a hallway or closet tank to reclaim interior space during a remodel
• Relocating equipment as part of a garage conversion or utility reorganization
• Adding bathrooms or fixtures that change hot water demand and utility routing
• Combining water heater work with kitchen or whole-house renovation permits
• Upgrading a duplex, ADU, or SB 9-related project where utility separation and space planning matter

In these cases, the water heater is only one line item in a broader set of permit drawings. If that sounds familiar, related use cases include measured plans for a kitchen remodel, a garage conversion, or a whole-house remodel.

California code topics can also intersect indirectly. For example, Title 24 energy requirements may affect associated work depending on scope and location, and local departments may apply their own submittal standards. On multifamily properties, separate maintenance or safety obligations such as SB 721 or SB 326 may already shape how exterior work is reviewed, even if they do not directly govern the water heater itself. Confirm all project-specific requirements with your local jurisdiction.

What your city, architect, or contractor may ask for

If a tankless water heater permit goes beyond a basic appliance replacement, plan preparers often ask for a measured base drawing before they start the proposed design. That request is less about bureaucracy and more about preventing avoidable mistakes.

You may be asked to provide:

• A current floor plan of the affected area
• Dimensions from the unit to adjacent walls, openings, or ceilings
• An exterior elevation showing the new location or vent termination
• Photos paired with measured drawings
• PDF and DWG files so the proposed work can be drafted efficiently

When these requests come from your contractor or designer, they usually mean the project has enough moving parts that a hand sketch is risky. A measured CAD background reduces uncertainty, especially in older homes where field conditions rarely match old permits.

If you already know you need documentation, you can review FastAsBuilt service options on the packages page before ordering.

What FastAsBuilt provides for California homeowners and project teams

FastAsBuilt produces field-measured as-built drawings and measured floor plans throughout California. Local crews serve Los Angeles, Orange County, the Inland Empire, the Bay Area, and San Diego. The workflow is straightforward: we measure on site with laser tools, then senior drafters prepare permit-ready CAD files delivered in PDF and DWG format.

For smaller documentation needs, 2D As-Built Plans start at $900 for up to 1,500 square feet, then $0.50 per square foot, and include one revision with typical delivery in 48 to 72 hours. For projects that need more spatial information, 3D As-Built Plans start at $1,500, then $1.00 per square foot, and include a 3D model plus 2D floor plans, elevations, and sections, with two revisions and typical delivery in 3 to 5 business days.

Turnaround times are estimates and may vary based on project complexity and scheduling.

Custom projects—including commercial spaces, ADUs, SB 9 work, tenant improvements, and other nonstandard scopes—are quoted individually. If you are comparing options, this guide to as-built drawing costs in California can help you understand the typical service structure.

For a tankless water heater permit, many clients only need a targeted measured plan of the affected area plus an elevation or section. Others use the opportunity to document the full property for future work. The right scope depends on whether the permit is isolated or part of a larger renovation path.

How to decide whether you should get as-built drawings before applying

If you are unsure whether to order measured drawings first, start by looking at the actual permit scope rather than the appliance label. Ask what is changing in the building, not just what is changing in the mechanical equipment.

• If the unit stays in place and utilities remain substantially the same, your contractor may not need a full measured plan.
• If the unit moves, venting changes, or wall penetrations are added, measured drawings become much more useful.
• If the project is tied to a remodel, addition, ADU, or conversion, existing conditions plans are usually worth doing early.
• If the property is older, attached, or visibly inconsistent with old records, measured documentation can prevent costly assumptions.

A practical approach is to call the local building department and ask what they want for your specific tankless water heater permit. Then ask your contractor, architect, or designer whether they can prepare the proposed scope from photos and rough dimensions, or whether they want a measured CAD base. If either answer is uncertain, as-built drawings are often the cleanest next step.

Frequently asked questions

Can you get a tankless water heater permit without as-built drawings?

Yes, sometimes. If the installation is a limited replacement in the same location with no major changes to gas, venting, electrical, or surrounding construction, the jurisdiction may not ask for measured drawings. But once the scope expands or the reviewer needs to understand the existing layout, as-built drawings or existing conditions plans become much more helpful.

Are as-built drawings the same as the proposed permit plans?

No. As-built drawings document the existing conditions of the property as measured in the field. Proposed permit plans show what will be changed or added. In many projects, the as-built drawing becomes the base file that your contractor, architect, or engineer uses to prepare the proposed sheets for submittal.

What if the old permits do not match the house today?

That is one of the most common reasons to get field-measured drawings. Older California homes often have undocumented modifications, utility relocations, or room changes. Using current measured conditions helps avoid designing around outdated records and can reduce permit comments caused by inconsistent information.

Do tankless installations ever need elevations or sections?

Yes. They often do when the unit is mounted on an exterior wall, venting passes through a wall or roof, or clearances and vertical relationships matter. A simple floor plan may not be enough to explain the installation. In those cases, elevations and sections can make the permit package much clearer.

How fast can FastAsBuilt deliver measured plans?

Typical delivery for 2D As-Built Plans is 48 to 72 hours and includes one revision. Typical delivery for 3D As-Built Plans is 3 to 5 business days and includes a 3D model plus 2D floor plans, elevations, and sections, with two revisions. If your project is unusual or commercial, FastAsBuilt can quote a custom scope.

Turnaround times are estimates and may vary based on project complexity and scheduling.

Bottom line

You do not always need as-built drawings for a tankless water heater permit, but you often need clear existing conditions information. If the installation is moving, adding venting, affecting utilities, touching exterior walls, or folding into a larger remodel, measured plans can make permit review and field coordination much smoother. FastAsBuilt helps California homeowners and project teams document what exists now so proposed tankless work can be designed and submitted with fewer assumptions.