House Plan Modifications - F.A.Q.:

How much will modifications cost?

Minor to moderate changes usually range from $150 to ~ $700.  If you should want to make extensive changes to a larger house, you may spend a few thousand dollars.   If that seems like a significant amount, remember that fully-custom house plans can cost as much as $5 per square foot, and the average stock house plan price is about $700. You're still saving thousands of dollars by choosing a stock house plan.  Also, keep in mind that requested changes may affect the total square footage�or width and depth�of the design.

In general, most people who modify a house plan spend between $300 to $1200 for the changes.  The cost is directly affected by the complexity of the changes and the amount of labor involved.  Your cost may be more or less depending upon the time needed to make your changes.   If an exterior wall is moved, then additional changes would be involved because the updates affect additional aspects of the drawings (such as the roof, foundation, exterior views, etc.).   If exterior walls are not involved, the cost is normally less.

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Do I have to pay for a modification estimate?

No,  if the designer of the stock house plan offers modification services, they will provide you will a complimentary estimate.  If  the designer does NOT offer these services then you may or may not be charged a modification estimate fee from the  architect, building designer, or draftsman that you contact to complete the requested modifications.

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What are the most commonly requested modifications to plans?

These include:

  • Eliminating windows, fireplaces, false dormers
  • Changing garages from a 2 to 3-car
  • Reconfiguring kitchen cabinets for appliances
  • Rearranging certain interior walls
  • Changing ceiling heights
  • Changing exterior surfaces (brick, siding, stucco)
  • Changing exterior wall framing (2 x 4 to 2 x 6)
  • Changing a foundation type
  • Relocating garage door openings / adding or eliminating bays
  • Changing garages from/to rear, front, or side-load
  • Kitchen or bath layout change
  • Changing an exterior elevation style. (Using the floor plan of one home and the exterior of another)
  • Adding or eliminating a room. (This would involve changes to all aspects of a plan - elevations, floor plans, roof, and foundation details)
  • Stretching house plans in either width or depth
  • Adding a bonus room over the garage
  • Reducing or increasing the square footage of the home

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    What type of Modifications are the most expensive?

    One of the most requested modifications is to reduce the size of the house.  Because many stock house plans have been designed with CAD programs, you might think that it would be simple to just instruct the program to reduce the size of the house by 10%, 15%, etc.   Actually, that can be done, but what happens is that everything gets reduced by that percentage � door & window openings, refrigerator openings, tub and shower spaces, etc. What happens is that the house doesn�t �work� anymore. The designer would most likely have to start from scratch at a flat rate of $1-$5 per square foot of finished floor space to get the size of the home reduced for you. Therefore, reducing or enlarging the size of a house is one of the most expensive modifications you can make.

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    Will the plans have all the information I need to get a building permit?

    In most cases, depending on the location where you are building your house.  Many local building departments will also require a site plan to show where the house will sit on your property.  You might also need beams sized to accommodate roof loads specific to your region.  Your home builder can usually help you with these type items.  If you are not connecting to a city sewer system, you also need a septic design attached to your application.  Also, certain areas of the country now require compliance with local energy codes, which is normally only a simple form that you fill out and attach to your application. 

    In some regions, you also need to ensure that your house plans are in compliance with local codes, including certain areas of North America which have more strict engineering requirements.  For example, earthquake-prone areas of California and the Pacific Coast,  hurricane risk areas of the Florida, Gulf, and Carolina coasts, as well as New York, New Jersey, Nevada, and parts of Illinois require review by a local professional.  If you are building in these areas, you will most likely need to hire a state-licensed structural engineer to analyze the design and provide additional drawings and calculations required by your building department.  If you aren�t sure, building departments typically can provide you with a handout, listing all of the items they require to obtain a building permit. Additionally, stock plans do not have a professional stamp affixed. If your building department requires one, they will accept only a stamp from a state-licensed professional where you plan to build.  In this case, you will need to have your house plans reviewed and stamped by a local building designer, architect, or engineer in your particular state and/or region.

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    Is it necessary to have plans modified? Can�t I just do the changes myself during construction?

    Often times, yes.  It is perfectly normal to do what is called "red-lining" changes you intend to make to the plans. Certain changes can be made during construction without modifying the house plan.  However, this is dependent on your local building codes and the flexibility of your local building department.  Always consult with your local building department and home builder to determine whether the changes you want to make are feasible without having the design modified.

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    Why do I need to purchase a "Reproducible" or "CAD File" set in order to have modifications made?

    For three reasons:  First, a "Reproducible" and/or "CAD File" plan package will include a Copyright Release so that whomever completes the house plan modifications will have legal permission from the original designer to alter the drawings, which are copyrighted and protected by Federal law.   Secondly, you will be sent the modified Reproducible after completion of the modifications and you will be able to make legal copies of the plans for your builder, lender, building department, and subcontractors.  (It is illegal to make copies of a house plan without a Copyright Release from the original designer).   Finally, Reproducibles are on a special type of semi-transparent paper that allows professionals to both erase and copy.  Regular blueprints are not erasable, nor are they able to be copied.

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    How long does it take to have modifications made?

    It varies; depending upon the designer's workload at the time and the complexity of the design.  In most cases, the modifications can be completed in 1 - 6 weeks.

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    Can your plans be adapted for handicapped accessibility?

    Yes, some plans will be easier than others to adapt, but there are always ways to modify plans to adapt to special needs.

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    Will my home plans come with a seal or stamp?

    Stock plans do not have a professional stamp affixed. If your building department requires one, they will only accept a stamp from a state-licensed professional where you plan to build.  In this case, you will need to have your house plans reviewed and stamped by a local engineer, architect, and/or building designer.

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    Do the plans include engineering?

    No. Even custom home designs don�t include engineering. Engineering is an entirely different profession. If your plans need engineering, you will need to hire a local professional familiar with engineering requirements in the location you intend to build.

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    Will my modified design include a Material List?

    Normally, no. However, many designers do offer an optional materials list for their plans at a minimal charge.  Please see the plan's detail page for additional information.

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    Will my plans conform to my local building code?

    All of our house plans are designed to conform to the local codes where the original house was built.  Most building codes in the United States are similar because they meet industry-standard minimums that are based on three nationally recognized standards. Building codes are standards created to ensure the structural safety of buildings.  They are established and enforced by your local government, usually through your city or county's building department.  Every state, county, and local municipality has adopted their codes from one of the three nationally recognized building codes: UBC (Uniform Building Code), BOCA (Building Officials and Code Administrators), and CABO (Council of American Building Officials). The new IRC (International Residential Code) is a combination of the other three and is fast becoming the National Standard.  All are very similar in content.

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    What if I don�t like the way the plans turn out after I receive the modified drawings?

    This is highly unlikely since you will have discussed the changes, in detail, with the designer, but in the event you don�t like the modified plans, the modification work will still need to be paid for.  Unfortunately, there are no refunds on modification services.  You will need to pay for the cost of the blueprint master and the cost of labor that has been performed for you.  For example, if you decide not to finish the final design phase then you are still responsible for paying for the cost of the blueprint masters and the preliminary design work that was done for you. The estimate that you receive will show you the total cost to complete the changes you requested and the estimate will usually be broken down in to two phases of design work. If your changes are fairly simple then there may only be one phase of design work needed.

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    Will the plans include electrical, plumbing & mechanical details?

    Location of heating,  air-condititioning, duct work & water heaters will not usually be shown on plans since local codes and climate, as well as your preference of heating and cooling systems, varies dramatically. Your builder and subcontractors will help you determine the optimal selection and logical placement of equipment. The only plumbing related information that will be on the plans is the location of fixtures such as sinks, tubs, showers, etc. Electrical schematics, (location of lights, plugs & switches) is typically included unless otherwise noted.

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    If you should have any questions about the house plan modification process, please don't hesitate to email us at questions@houseplancentral.com, and we'll be glad to walk you through the process.

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    Learn more about the house plan modification process:

    Modifications Basics

    Modifications Frequently Asked Questions
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