How much does an ADU cost in San Mateo County?

Accessory Dwelling Units (ADUs) are on the rise and for good reason. These small, secondary homes built on the same property as an existing home offer various benefits, especially for homeowners in San Mateo County. But how much does it cost to build one? In this blog, we’ll explore everything you need to know about the cost of building an ADU in San Mateo County, from different types of ADUs to real-life examples and permit processes.

What Is an ADU and Why Are They Gaining Popularity?

ADUs, also known as granny flats or in-law units, are becoming increasingly popular in San Mateo County. These units offer a flexible living solution by providing additional living space without the need for a separate property. They can be used for various purposes such as housing elderly parents, generating rental income, or providing a private space for guests.

The demand for ADUs has been growing as more people recognize their value. For homeowners in San Mateo, this trend offers an opportunity to maximize property use while addressing housing shortages. With housing prices skyrocketing, many are turning to ADUs as a cost-effective and practical solution.

Benefits of Having an ADU in San Mateo County

Investing in an ADU offers a plethora of benefits. First, it adds significant value to your property. Real estate experts agree that properties with ADUs often have higher resale values. Second, they provide a source of passive income. Renting out an ADU can help offset mortgage payments or other expenses.

In addition, ADUs offer the flexibility of multi-generational living. Families can stay close while maintaining their privacy. Lastly, ADUs contribute to solving the housing crisis by providing affordable housing options without the need for new land.

Factors Contributing to ADU Costs

Several factors contribute to the overall cost of building an ADU. Understanding these can help you budget more effectively and avoid surprises.

1. Size of the ADU  

• Less than 500 sqft
• 500-750 sqft
• 750-1000 sqft
• 1000-1250 sqft

2. Materials Used  

The choice of materials can significantly affect the cost. High-end materials will naturally increase the budget, whereas more basic options can help keep costs down.

3. Labor Costs  

Labor is another major factor. Depending on the complexity of the project and the rates in your area, labor costs can vary widely. Hiring experienced contractors might be more costly upfront but can save you money in the long run.

Detached ADU Costs

Detached ADUs are standalone units that are not attached to the main house. Here’s a breakdown of the costs based on size:

• Less than 500 sqft: $120,000 - $180,000
• 500-750 sqft: $140,000 - $215,000
• 750-1000 sqft: $160,000 - $250,000
• 1000-1250 sqft: $215,000 - $325,000

These costs include materials, labor, and any required permits. However, additional features like custom finishes or high-end appliances can push the cost higher.

Garage Conversion Costs

Converting an existing garage into an ADU is often less expensive than building a detached unit. Here are typical costs:

• Less than 500 sqft: $100,000 - $165,000
• 500-750 sqft: $130,000 - $190,000
• 750-1000 sqft: $160,000 - $240,000
• 1000-1250 sqft: $190,000 - $295,000

Garage conversions are ideal for homeowners looking for a more budget-friendly option. They make use of existing structures, reducing the need for new construction.

Attached ADU Costs

Attached ADUs are built as an extension of the main house. These units offer the convenience of being close to the main living area while providing separate spaces. The cost for attached ADUs falls somewhere between detached units and garage conversions, making them a versatile option for homeowners.

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Real-Life Examples of ADU Projects in San Mateo County

To give you a better idea, let's look at some real-life examples of ADU projects in San Mateo County:

Example 1  

A homeowner in Redwood City built a 600 sqft detached ADU for $150,000. The project took six months from start to finish and included custom cabinets and energy-efficient appliances.

Example 2  

In San Mateo, a family converted their 400 sqft garage into a cozy ADU for around $120,000. This project was completed in three months and now serves as a rental unit, generating an additional $1,500 per month in income.

Example 3  

A larger project in Burlingame involved a 1,000 sqft attached ADU, costing $250,000. This unit includes two bedrooms, a full kitchen, and a living area, offering ample space for extended family visits.

The Permit Process for Building an ADU in San Mateo County

Before you can start construction, obtaining the necessary permits and approvals is crucial. Here are the steps involved:

1. Pre-Application Meeting  

Meet with local planning staff to discuss your project and understand the requirements.

2. Submit Plans  

Submit detailed plans for review. This includes architectural drawings, site plans, and any other required documentation.

3. Plan Review and Approval  

The plans will be reviewed by various departments, including zoning, building, and fire safety. Make any necessary revisions based on feedback.

4. Obtain Permits  

Once approved, you can obtain the required building permits. Be prepared for inspections throughout the construction process to ensure compliance with local codes.

Conclusion

Building an ADU in San Mateo County offers numerous benefits, from increasing property value to providing additional income. While costs can vary based on size, materials, and labor, understanding these factors can help you plan more effectively. By following the permit process and considering real-life examples, you can make informed decisions to successfully add an ADU to your property.

Ready to explore your ADU options? ‍Contact us today to learn more about how you can get started on your project and make the most of your property.

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