Some of the most common enquiries I get are people who are looking to buy some land, or some land with a run down property on it, and who have a vision of transforming it into the property they have always dreamed of. I love working with these clients in helping them realize their dream but I also see it as my job to help them understand the challenges as well as the rewards.

Whether someone is looking to build something from scratch or take on a rural project in Sonoma County, I am sure you can imagine there are a lot of things to consider that relate to planning, building permits and land usage. Below I have tried to highlight some of the main considerations as well as share links to many of the key resources that a buyer can use as part of doing initial research as well as going through the process of due diligence as part of a purchase. 

Water – Wells

In order to support a single family residence Sonoma county requires that you have a minimum of 1 Gallon Per Minute (GPM) but many properties will have 2-5 gallons per minute. For a property at the low end of the accepted range, the owner would also want to have a 5000 gallon water tank to store additional water. Once an offer has been accepted on a property, a buyer should conduct a well inspection and water test. The cost of this will vary but will be approximately $750. The main purpose of this inspection is to verify the flow rate of the well in GPM and also to test the quality of the water.

Well Inspectors


Sanitation – Septic System

The other key requirement to consider is the sanitary system. Most country properties will be on a septic system but there are a few that still have cess pools although these are no longer allowed since the rules changed in summer of 2019. Another recent change to the rules means that if a septic system is not functioning correctly, rather than repair it, the regulations now state that you have to upgrade the entire system which is why septic inspections are more important than ever as part of the buying process.

The process for determining whether a property will support a septic system is a multi-stage process. Firstly, a third party company such as BC Engineering needs to conduct a soils test to determine the type of soil (clay, loam, sand etc), then carry out a pre-perc test under the supervision of the county which involves digging holes at a number of potential sites for the septic system to determine the speed with which water drains through the soil.

Once this is completed a full perc test must be under the supervision of a registered civil engineer. The company will then typically map out the contours of the land and do a preliminary design of the septic system to determine the size of the septic system, and thereby the number of bedrooms, the land will support. Prior to the close of escrow, buyers should get the septic system pumped and inspected which will typically cost $700.

Septic Resources
BC Engineering is a good company to work with to establish the septic system a property will support:  
Quality Septic Service (and inspections): +1 707 585 9000


Composting Toilets

Composting toilets are not currently permitted under the Sonoma County rules, however there is a trial underway at present to determine their viability if the waste is hauled off site by a licensed operator. This would not however eliminate the needs for a septic system as this would still be need to support grey water waste although it would considerably reduce the size of system needed.

Septic and Well FAQ: This is a good resource on the Sonoma County Website for getting a better understanding of septic and well requirements

Property Maps

There is a great resource on the Sonoma County website where you can put in the address or property APN number and overlay a google map onto the parcel map so you can see exactly where the boundary of a parcel is. Using this resource you can really drill in to see incredible detail.

Parcel resources


Permit History

Sonoma  County has a permanent record of all the permits that have been pulled on a property which should be reviewed as part of the period of due diligence. While it doesn’t guarantee it contains every permit ever pulled it is a great resource. In addition to looking online, it is also worth visiting the county to pull more detailed information on specific properties such as drawings and plans submitted to the county.

Permit resources


Zoning Codes

Every property has a zoning code which defines the purpose for which land can be used whether it be agricultural, residential or commercial or a combination of all three. While there are numerous codes there are a relatively small number that cover 80 per cent of properties in Sonoma County. There is a simple nomenclature which applies to many of the code designations. For example, RR is the designation for a Rural residential property. RR20 signifies that one residential property is permitted for every 20 acres. A number after the zoning code shows the amount of land that needs to be designated per residential property.

Zoning Resources

Zoning code descriptions

Online Appointments At Sonoma County Planning

It used to be that a visit to the Sonoma County Planning office was an all day affair. However, Sonoma county Planning has, somewhat, embraced the online world with a mobile app that enables you to book an appointment with any number of departments. 

Appointment resources
Download the QLess mobile app to book an appointment: 
Home Inspections
Purchasing a rural property with a run down building on it is no different from purchasing a track home in that you would want to have a full Home Inspection prior to purchase. The purpose of the home inspection is to visually inspect the major components of the structure for signs of significant none performance, excessive wear or general state of repair. The home inspection will not inspect the well or septic system and will only do a visual inspection of the roof. The cost of a home inspection will vary depending on the size of the property but approximately $450 up to $1000 on the largest homes


Home Inspection Services

Pacific Inspection Services: Eric Marsh

Tri-County Certified Inspections: Lance Woods 707 318 6428

Pest Inspections

As with a home inspection, a pest inspection is something a buyer should do prior to purchasing any property (unless one has been provided by the seller in which case it is down to personal choice). The main purpose of a pest inspection is to determine the presence of wood destroying pests and organisms. The inspection is largely a visual inspection and is limited to the areas that are accessible. An inspection will highlight two levels of damage: section 1 and section 2.

Typically a seller would be expected to pay for the repair of section 1 items.

Section 1: Items noted in a pest inspection report where there is evidence of active infestation, infection or conditions that have resulted in or from infestation or infection (i.e. fungus, dry rot, etc.).
Section 2: Items noted in a pest inspection report where conditions noted are deemed likely to lead to infestation or infection but where no visible evidence of such was found.

A pest inspection will typically cost $350. The following are a couple of recommended Pest Inspection companies:

Pest Inspectors


Pool Inspections

For any property with a pool it is advisable to get a pool inspection which provides a report on the current general condition of the systems and components of the pool and spa and to identify parts of the pool system that are suffering from readily observable deficiencies or are in need of repair.

The cost of a pool inspection is typically $450 and can be provided by the following companies: 

Pool inspectors


Secondary Units

With a rural property, a lot of buyers are keen to understand whether or not it will support a secondary unit. If a property is over two acres, it is possible to have a secondary unit up to 1200 sq ft, if the property is less than two acres the maximum size is 640 sq ft. However, if the unit has an additional bedroom, the septic system will need to support the increase in bedroom count.

Sonoma County resources: 


General Permitting Rules

One thing to bear in mind is that if you buy a property that has certain buildings or systems that are not permitted, if you then pull a permit to do significant work, you will most likely to have to ensure the entire property is up to code. For example if you have a septic system on a property which is an older system, if you add a bedroom to the property, then you will likely have to upgrade the entire system.

Permitting Resources

This content is not the product of the National Association of REALTORS®, and may not reflect NAR's viewpoint or position on these topics and NAR does not verify the accuracy of the content.