ADU Grading Plan For Perfect Building

When permitting an accessory dwelling unit, some regional governments may demand to obtain a grading plan prior to ADU development. The reason behind it is that an elaborate site plan provides ADU builders with additional information about any particulars of your property. It helps to prevent any future challenges when the construction begins.

In this article, we’ll delve into the details of such documentation as grading plans and soil reports, determining when they’re necessary and why.

Pre-Approved ADU Plans: When Needed

A site plan, a grading plan, a geotechnical report, and many other documents that describe your land belong to pre-approved ADU plans that state law may require homeowners to submit. Currently, the grading plan is not a mandatory document in the majority of cases.

Nevertheless, it makes sense to procure this document in the following cases:

1. Unusual land’s shape: difference in land elevation like steep slopes or hill areas;
2. Concentrated rainwater areas or swampy areas;
3. Land prone to soil erosion;
4. The land has existing structures on it;
5. Land has protected natural objects that demand special constructional considerations.

To sum up, basically anything that is not a flat lot may require a grading plan. It may not be mandatory in certain California jurisdictions, but building a new construction taking into account the unique property conditions is a wiser decision in many cases.

Implementation of Grading Plans

So, what details about the property does this pre-approved ADU plan provide? A grading plan encompasses the detailed descriptions of the land features listed below:

• Terrain overview (land’s topography, including the boundaries of the land, its slopes, and its elevations);
• Present parcel condition (state of vegetation, presence of utilities, or other constructions);
• Specifications regarding drainage (drainage system design to deter water leakages during construction works);
• Specific modifications for an accessory dwelling unit (presumable location of an ADU with respect to setbacks and overall site layout)
• Traffic flow opportunities (pathways, access to driveways, parking lots);
• Export or import of soil for foundation (in case of poor soil condition, a homeowner may request soil export or import for better support of the construction);
• Raised foundation considerations (to avoid flooding or risks associated with a steep landscape, the construction may demand additional resources for raising the foundation).

All in all, an elaborate grading plan ensures better adherence to ADU building requirements, enhancing the design of the ADU as well as the lot’s overall functionality.

ADU Plans: Effect on Grading Plans

Some homeowners opt for pre-approved ADU plans rather than choosing the layout on their own. The reason behind this is that such plans usually already comply with all ADU-specific requirements and are easier to submit.

Let’s explore different factors that you need to take into account when choosing the ADU suitable for your parcel:

• Variety of ADU Types

ADU studios, garage conversions, or two-bedroom ADUs? There’s no right answer until we know the unique features of your property. Is it single-family or multifamily housing? Does your county allow two-story structures? Consider factors such as architectural style, special amenities, number of occupants, and intended use to determine the size and configuration of your ADU.

• Land-Specific Factors

If your ADU occupies land with rocky outcrops or substantial slopes, modern design solutions may be required to integrate your ADU into the landscape of the existing area. Or, if your parcel is in a flood-prone zone, you’ll need a more complex drainage system to manage stormwater runoff. Also, the roots of mature trees can pose a challenge for digging, or the trees may even fall under nature preservation laws.

• Feasibility of ADU Integration

The more suitable your ADU plan is for existing conditions, the easier the construction. Thus, the property owner should pay attention to such factors as the construction of retaining walls, the required reshaping of the site topography, the application of soil erosion control measures, etc.

• Seeking the Help of Professionals

Specialists like ADU builders encompass engineers, designers, and architects who can give you a review of how to make the best use of your plot. They will help you pick an ADU that minimizes grading and other building challenges and fits into the scenery in a nice way.

• Customized ADU Solutions

Some ADU plans offer flexible features that adapt better to a particular sort of property. For instance, if your property has uneven terrain, the ADU plan may include different flat platforms that connect to each other in order to support the construction. Or, if your area is prone to floods, you can create a high-rise foundation for water damage protection.

Selecting the right ADU plan is half the success because it can reduce your costs and make the whole construction process easier and faster.

Grading Plans Submittal

Is it easy to submit a grading plan? In fact, the process may differ in complexity depending on the lot size, specific regional regulations, and the peculiarities of the site condition.

Usually, the preparation and submittal of a grading plan involve a few stages, such as a physical survey of the parcel, the collected data getting processed, the development of the grading plan, and ensuring that the plan adheres to all legal requirements. Moreover, it includes actual plan implementation: re-shaping the parcel in accordance with your plans by digging, moving, and raising the ground level to achieve the perfect environment for future buildings.

Mainly, the preparation and submittal of grading plans take from a few weeks to a few months. If grading plans fail to abide by local regulations or required standards, local governments may reject them. 

The fees also vary depending on the size of the lot and the complexity of the grading plan. They may range from several hundred to several thousand dollars.

ADU and Soils Reports

Additionally, to grading plans, some parcels necessitate a soil report. This kind of report evaluates the soil condition from the point of view of suitability for the ADU foundation. It’s required to identify any risky soil conditions. For example, soils with a high clay content expand considerably when moistened and shrink when dried. This can lead to considerable issues, such as the instability of built structures or the gradual settling of the foundation.

To maintain the long-lasting integrity of an ADU construction, there are two essential steps in the soil report process. They include:

• Preliminary site check

This stage takes place before any grading activities. The professionals inspect the site and create a report. They would analyze the type of soil (rocky, sandy, clay-like, etc.), its characteristics (soft, hard, etc.), and how it might affect your property in the long run.

• On-the-ground testing

During excavation, engineers carry out the review to ensure that the actual soil condition aligns with the stated one. They perform tests like examining small samples of soil and using equipment to double-check that the soil behaves as expected.

Not all cities require mandatory soils reports, but, for instance, some coastal cities do. This is contingent on the unique soil conditions, like exposure to soil erosion caused by saltwater intrusion and marine deposits.

While soil reports cost around $3,000, their absence can lead to unpleasant challenges during foundation digging. In this case, you’ll have to make changes to the already established ADU design, resulting in extra expenses.

Foresee the Fees

In the earliest stages of ADU development, we estimate whether you need any of these plans or not to ensure you become aware of extra expenses from the get-go. If civil engineering is unavoidable, it may raise the overall cost up to $5,000–25,000.

However, if you skip these steps, it may lead to poor scenarios. Not only may the city council refuse to issue a building permit, but the whole project may also be under threat. If the site has inherent challenges unknown to the builders, the construction can break at later stages of the building or during ADU use, threatening the well-being of all the residents.

We do our best to perform a quality job to achieve a long-lasting result that fulfills safety requirements. That is why we recommend investing in grading plans and soil reports if there is any risk.

Frequently Asked Questions — FAQ

What is a grading plan in construction?

In ADU (or primary residence) construction, a grading plan is a detailed document indicating the current condition of a piece of land. It also shows what changes homeowners should make and what resources they need to ensure compliance with ADU building regulations and guidelines.

How do you read site grading plans?

Site grading plans provide up-to-date information about the reviewed land as well as modifications required for the creation of a new ADU. This may include the topographical features of the parcel, its drainage system, requirements to maintain soil condition, etc.

What does grading mean when building a house?

Grading the land means shaping it when preparing for a future construction project. Note that it encompasses not only leveling for the creation of a solid foundation but also drainage of the land to make up the proper water flow withdrawal in the right direction from the parcel.

Can you build an ADU before the main house in California?

Technically, the law permits you to construct a small residential unit before your primary residence. However, note that this type of development will count as your main house. No matter the design, the first building is not an ADU because an ADU is a secondary building created in addition to the main one.

What are the main construction restrictions for an ADU?

Lot coverage, floor area ratio, and established setbacks are the main rules that limit the location of your ADU on the land, as well as other ADU building criteria like ADU height and allowable building footprint. Only the design that does not contradict them can receive a permitting document.