10 Things to consider when buying a home that you plan to expand. 

 Author: Claire Dosen

Claire is a 5th-year Landscape Architecture student at Cal Poly, with a background in residential construction. She is very passionate about ecology, the built environment and public lands.


Finding a perfect home to fit all your needs and wants can prove to be a difficult task.  Many of the most sought-after neighborhoods were built more than 50 years ago.  These homes were designed to meet the needs of prior generations, not the preferences and needs of today’s families.  Few properties offer perspective buyers the “perfect” home but expanding and renovating an existing property is an excellent way to end up with your perfect home in your preferred location and/or school district.

Here are ten things to consider when buying a property that you intend to expand.

  1. Start at the end.

First, think about what you want to end up with. How many square feet, style, layout, number of bedrooms and bathrooms? After renovations and additions are completed, how much outdoor space will you, your family and pets need? It is crucial to have a vision to work towards.

A good tip is to find your dream home (outside of your preferred neighborhood) that meets all your space needs and consider it your “template”.  You’ll want your “template” home to be on a similar lot size as those available in your preferred neighborhood.


  1. Find a home you can work with in your preferred location.

This is your “target” home. After you’ve thought through what you want, it’s time to inventory what you have to work with in your target home.

Say it is a 2 bed, 1 bath home on a large lot, but you want a 4 bed 2 bath home. You’ll need to add two additional bedrooms and an extra bath. The difference between your “template” home and your “target” home is roughly the size of the addition you will need to build.

You’ll also need to determine whether to build up or out? The initial lot size is big, but you want to preserve your large yard for entertaining, the kids and a garden.  Expanding up costs 10-20% more and can be more complex to permit but allows you to retain precious yard space; expanding out eats into the yard but may offer layout advantages for an open-floorplan living-room/kitchen.


  1. Do a price check.

Use the estimated additional square footage calculation you made in Step #2 to rough-out a budgetary range for your renovation/addition.

Look into building costs in the area where you are searching for your new home. Building costs typically run higher than anticipated so add an additional 10-20%. A great way to gain some insight into cost per square foot, is by asking someone who recently finished a project of similar scope. Friends, family, or your realtor may be able to connect you with one. Once you roughly determine the cost to build your Addison/renovation, you should have a good sense of what your addition/renovation will cost.


  1. Check the Zoning Code.

If time allows prior to purchasing your to-be-expanded home, you, your Architect or Designer should check your local zoning code- it may help you identify (at a high-level) some of the limiting factors that may constrain your project. Check the parcel-specific set-back requirements from your property line- they impact how far out and up you can build, defining the limits to your overall vision.

In addition, if there are any additional detached structures like a garage or accessory dwelling unit, determine the necessary clearance between the main house and other structures. Required clearance is typically between 7’-15’.

Once you have looked at the zoning code and learned the requirements, do a test fit to see if your desired addition size and shape will fit on the lot in the location you prefer while meeting the clearance and set-back requirements.  Google earth’s measuring tool is a good tool to test fit a future addition.


  1. Consider the shape of your existing building.

When looking at potential homes to expand, you’ll want to minimize costly structural changes, so you can put your money into high-quality materials and finishes and adding additional space.  Structural elements such as roof pitch, ceiling height and overall building shape are expensive renovations.  So, best to find a house that already has the shape, ceiling height and roof pitch you like!


  1. Pick a home with large rooms.

Avoid structural wall-removals, if possible.  Given two homes with the same square footage, choose the one with larger rooms– especially if you want an open floor plan. Homes with large rooms allow for more possibilities without having to pay for structural wall removal. Interestingly, homes with existing large rooms and larger spans likely are already engineered with larger beams and foundations. This can be helpful during renovation to help you achieve your desired layout.


  1. Avoid awkward layouts.

Awkward layouts such as multiple mid-level changes or funky room shapes can spell disaster for your budget!  These structural changes can eat-up a large portion of your budget without adding new square-footage or the lux finishes you dream of!


  1. Make the old new.

Compared to costly structural changes, exterior finishes such as siding, windows and light fixtures are relatively inexpensive items to change out. This is where you want to put your money- it is the “eye-candy” that will make your home shine! Targeting properties that have not been renovated, allows you to keep the purchase price down and choose the finishes you really want.


  1. Find a large lot.

If all things are equal when choosing amongst properties, choose the one with the larger lot and kitchen towards the back of the house.   This allows more space for first-level expansions and enables expansion of the kitchen where there it is usually less constrained (by set-back lines).   It also allows for an indoor-outdoor lifestyle with sight lines and access directly to your backyard.


  1. Get the most value.

Whether your goal is to get the most value or renovate to create your dream home, in high-cost real-estate areas like SFBA, adding new square footage usually delivers great value for your renovation investment (sometimes, doubling your investment), so it makes sense to maximize new square footage to meet both goals.  In low-cost real estate areas, building an addition may not offer a good return-on-investment.


Despite many aspects to consider when purchasing a home for expansion, it is a great way to purchase in your desired location and end up with an amazing home that meets all your needs! With your end vision in mind, these steps can help in choosing the right home for you to make your dream home a reality!



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