How Much Does an Addition Cost?

Type in your Online Search for "I want to Build an addition – how much will it cost?" or "How much will my home renovation cost?" or "How much will my home remodeling project cost?" You'll be flooded with links to third party platforms that invite you to connect with local professionals to connect for a free estimate. As you scroll down, you'll find a few articles listed by remodeling companies.

These questions are top of mind for homeowners considering building an addition or doing remodeling or renovation work to their home. It's normal to want to know if everything on your wish list fits with your budget available for the project. The sooner you can determine if your budget is realistic to accomplish your vision, the sooner you can move ahead to realize your dream. Like many questions that might seem simple on the surface, the answers are not simple at all. Your home is a one-of-a-kind building in a unique location, even if it is a tract home where your neighbors have a home with the same floor plan. Your vision and dreams for your home addition, remodeling or renovation project are uniquely yours and unless you are interested in a prefabricated sunroom or some other premade product (and even those will have different installation requirements depending on your home conditions), there is no box on a shelf with your project in it. This makes it challenging and at times very difficult for design builders, architects, designers, remodeling contractors, builders and other industry professionals to answer your question "How Much will my Addition Cost"?

To answer to the question "How Much Does an Addition Cost?" It is important to define what an addition is. An addition is new space added onto an existing structure (I'll use the term home or house since this discussion will be focused on residential homes). New space may include enlarging the footprint of the home, cantilevered "bump outs", adding a new floor on top of an existing house, building dormers into the roof or a combination of the above. New space usually refers to new or expanded finished living space, such as kitchen, family room, living room, dining room, bedrooms, baths etc. Additions may also include garages, carports, "she sheds", workshops, storage sheds, barns and other accessory buildings that have foundations and roofs. Decks, patios, lanais, and other exterior improvements are often done in conjunction with an addition project but are generally considered as stand-alone exterior home improvements if done separately. 

Remodeling and renovation projects are focused on updating or rebuilding existing living spaces. There is always some remodeling or renovation involved when an addition is built at the connection area of new to existing. In some cases, there is extensive renovation and reconstruction of existing space to accomplish the owners desired design goals.

Back now to the question: "How Much Does an Addition Cost?"

Well, great question – the answer is - it depends. Let me explain…..

Your addition will be unique to you and your home – it is a "one of a kind" project that doesn't exist in a box on a shelf anywhere. You will be in control of every decision along your journey of designing, planning, budgeting and ultimately building your addition. You must translate your vision to a specific plan and set of selections that define your project so that the appropriate professionals may price it out for you. Someone might answer your question with a question: "How much do you want to spend? or What's your budget for your project?" In this case your question is really "How much addition can I buy with my budget?" This might work in some cases, but it's likely this approach will prove unsatisfactory.

At this point I'd like to emphasize how critically important a thoughtful, detailed evaluation of your project budget amount really is. The following case study is a true story. It took place over the past year. The owners asked a local contractor how much their addition and whole house renovation project would cost. The contractor visited the property and "ballparked" the project at about $500k. The owner hired a building designer to design and draw up permit plans for the project and secure the building permit. The owners secured financing for the project based on the $500k "ballpark" construction amount. The plans went through nine revisions and rounds of comments with the local jurisdiction building department and were approved for permit. The contractor started pricing the project in more detail once the plans were approved for permit. The contractors price came in nearly 20% over the $500k "ballpark" and did not include approximately $125k of cabinetry, appliances, fixtures etc. The actual price for the owner to build their project was over $700k. The owners did not have additional funds available and had already secured financing based on the $500k ballpark amount. The project was put on hold indefinitely. Everyone was disappointed and upset, especially the Owner. Had a more thorough pricing evaluation been done while the design was being developed it would have become apparent that the project design would require more than the "ballpark" amount and the Owner could have made changes to reduce the amount or increase funds for the project or a combination of both approaches to arrive at a project the Owner was happy with in every way and could afford to build. This sad story has been experienced by countless Owners and it's a major reason why we believe strongly in the Preliminary Design and Feasibility Study approach, which brings these issues to the surface early on in the design process. No homeowner enjoys spending precious time and money designing a project that they cannot afford to build. The same process occurs when Owners hire architects to design their dream project and there is no financial analysis done to confirm the projects financial feasibility for the Owner. The idea that one can "squeeze" money out of the project budget by soliciting the lowest bid they can find often results in unfinished projects, shoddy workmanship, and other unsatisfactory outcomes.

Designing and building an addition consists of many components and variables.

One realizes quickly there are endless combinations of different phases of the process – each one will influence project scope of work and the investment amount (budget) for the addition. The general answer to your question is that your project will cost what you determine is the right amount to accomplish your vision and meet your quality and performance requirements. To refine and quantify that amount is what the ensuing discussion is about.

The primary variables that impact cost are size of addition, architectural style, type of rooms to be added and/or renovated (for example kitchens and bathrooms are more expensive than bedrooms), site access factors and challenges, plumbing, electrical and HVAC system integration issues, quality level of exterior materials as well as interior finish selections and specialties. Each of these variables must be accounted for based on your homes design and site conditions. One example is electrical work. You want standard "to code" electrical work and your homes electrical service is sufficient to power your electrical scope of work. In this case, your electrical budget would be at the lower end of the range for electrical work (prices do vary between electrical contractors). Perhaps you desire an extensive lighting plan with a smart switching system and several new appliances which require dedicated circuits, and your main electrical service will need to be upgraded to power the new electrical design and devices. In this case, your electrical budget will be significantly higher, based on the actual work required. The concept outlined in this example applies to every variable of your project, As you begin to realize that it is an involved process to define the scope of the work you would like to have done, integrated with what you must to do to comply with safety and code standards, not to mention the additional craftsmanship needed for your higher level architectural design choices, you realize the answer to your question is a complex one.

Without evaluating the variables involved in your project, and determining which one or two (or more) will be "more than average" (for any number of reasons), the best anyone can do is guesstimate what budget range your project might be in. A term for this is Preliminary Rough Budget Range. These ranges tend to be wide, not very specific, and not a budget you can plan on. For example, you want to build a single level 800 SF addition. The preliminary rough budget range could be anywhere between $160,000 - $650,000, or more. This budget range is not useful because it's so wide. Budgets need to be based on specifics. You would be well served to discuss preliminary budget ranges with experienced professionals who have a history of building similar projects which they can reference to determine a realistic preliminary range that is based on actual built past projects of similar size and scope. Preliminary Rough Budget Ranges based on the above will still be somewhat wide but more useful as a starting point for further discussion.

A big question at this junction is: are you ready to put the time into planning your project so you can obtain a specific answer to your question: "How much will my addition cost?" 

There are several different methods owners may choose from to do their home addition project. Depending on the method you choose the amount needed to do your project will vary. The amount of time and energy to manage your project will also vary. Owners can choose to self-perform the work and hire specialty trade contractors as needed (plumber, electrician, HVAC etc.) They can act as Owner –Builder and contract out each phase of the work (essentially taking on the duties of Construction Manager). Owner may choose to hire an architect to prepare plans and solicit "bids" from various contractors or the Owner may choose to retain a Design Build firm to coordinate the design and construction of their project. Each method has its pluses and minuses and impact on project investment. This article will focus on project delivery performed by a professional design builder or architect and general contractor. See Blog Post Article: "Design-Bid-Build" for more information.

What's really great about the design build process is you are able to decide what your final outcome will look like and how much it will cost. You will be able to create your masterpiece, it will be uniquely your own. This will take a serious commitment of time and resources on your part. but the results will be worth it. There are many "horror stories" of projects where the planning details were incomplete, and the results were unsatisfactory for the owner. None of my clients ever said they regretted taking the time to work through the details. They have commented, however, that they realized how involved and complex a process it was to design and build their project, and that they were very grateful to have experienced professionals take care of their project for them.

The above factors will be determined by your homes' existing site conditions, your design choices and material selections. Until these factors are discussed, and your guidance given it's practically impossible for any company, architect, building designer, contractor, builder or remodeler to presume to know your preferences for the variables listed above. Once those are defined the process of designing and building your home addition and determining its budget can get underway in earnest.

Regardless of the method utilized to manage the construction process the list of Construction Phases remains the same. Most additions have at least some works in each of the following categories, so it is very important to not broad brush over any category too quickly when developing a project budget. Each category has hundreds, and sometimes thousands of items that might be used. The list of detailed items is exhaustive and not appropriate to get into at this level, but I will address each Phase of the work in subsequent articles. Suffice it to say that an addition will usually include work in all phases, with several requiring additional work to ensure a thorough project (for example the entire roof may be replaced with the addition, or a new HVAC system installed to condition new and existing spaces, or enhanced insulation installed in the existing home to improve comfort and reduce energy use).

The general outline of the Major Phases that must be evaluated to determine a project's cost are:


These Major Phases provide an outline to use for estimating your project investment amount. Most homeowners are not prepared to do a detailed estimate for their project. Most builders, contractors and remodelers are not in the position to be able to provide you an accurate estimate until your project is designed and specified. Hence, the dilemma owner's face – How much will my addition cost? The answer - it depends on a set of variables not specified, results in a less than satisfactory answer for someone who is seriously considering a project and genuinely wants to know how much money it might take to build their project.

There are websites one can visit that display SF pricing for room additions of various sizes. Buyer beware of this information, which is generally not inclusive of all work that will be required for your addition project, and it does not benefit homeowners to have an incomplete budget when planning a project. Research has discovered many of the websites offering SF prices for additions and additions are not websites of companies that provide building or remodeling services, but websites of third-party marketing platforms that seek to capture job leads to sell to contractors and designers. You can find pricing for plumbing and electrical fixtures, and many other building material products online but there is very little authentic pricing information available online regarding building and remodeling services.

Let's take a quick pass thru the Construction Process Phase list. Plans & Permits is the phase where the scope of services and investment amount for your project architectural design, engineering design, interior design, sustainable design, surveys, zoning issues, building permits and special inspections are identified.

Each one of these services scope of work can vary a great deal. For instance, if you retain an architect to provide full-service design, from concept through design development and including permit plans and construction documents you can expect fees in the 10-15% range (based on projected construction budget, which does not include construction inspection and administration). Engineering fees would be in addition to the architectural fees, as well as surveyor, interior design, sustainable design fees as well as building permit fees and any special impact fees your jurisdiction might levy. In the event you retained a Design Build firm your design fees will likely be less than the full-service architect, but this will vary by firm. It is very important that you find the best fit for your needs and style for your project. This decision is perhaps the most important one you must make regarding your project. See Blog Post article "Design-Bid-Build" for a more in-depth discussion on this critical topic.

Assuming your project complies with your local zoning regulations, depending on the jurisdiction that has permitting authority for your project there will be different requirements for permit plans and building permit fees. Your building designer or architect should be able to guide you through the entitlement process to help refine the feasibility of what you can build on your property without a variance, as well as determine what must be done in the event special conditions effect your property.

Type of zoning, allowable building size, height, setbacks, shoreline setbacks, conservation district restrictions, historical or fine arts district requirements and other factors come into play regarding zoning feasibility of your project. These issues should be identified, and solutions worked out very early on in your planning process. You should know that not all zoning issues are easily identified, and it is important to do your due diligence in this area carefully and early in the process. Once done, important design parameters are established that must be complied with, which is much easier to do when you are aware of the issue from the start.

Resolution of this issue also allows for refining the investment needed to accomplish design solutions.

Tear Out is next on the Construction Process Phase List. An important and often underestimated category this is where everything that must be carefully removed, demolished, dug up and hauled away must be identified and accounted for. Testing for hazardous materials which may be present and need to be abated properly to comply with safety, health and code regulations and laws must be done and proper procedures followed. Hazardous material removal and/or abatement, such as asbestos pipe insulation, asbestos tile/siding/roofing, lead paint etc. generally are done prior to major demolition to avoid contamination of the site or the environment. In some cases, an industrial hygienist must test air quality for safety after abatement and before work may continue. Temporary Protection is an important and often overlooked task that is very important when you want to save existing materials or finishes for re-use. It is also required to protect work put in place that must be protected from damage during the rest of the construction process. What type of disposal will be utilized to handle debris from tear out and demo? Debris from ongoing work? Dumpsters? Trash hauling trucks. Re-cycle? All these factors must be analyzed and accounted for.

Is your project a candidate for a de-construction firm to salvage building materials for re-use? Many local jurisdictions have resources available that offer deconstruction and you may receive a tax deduction for the value of materials salvaged, or you deliver materials to a Re-Use warehouse and are able to take a charitable donation. There are many deconstruction, recycling and environmentally responsible material handling options available.

Your home will have a unique set of Tear Out circumstances that will need to be addressed to execute your project properly. Depending on the requirements the investment amount to accomplish the work will vary. Tear Out definitely depends on your specific site.

Excavation is the next major Phase on the Construction Process List.

If you are building an addition, you will require a foundation. (Unless you are doing a cantilevered bump out). Depending on your building code requirements and the climate zone you are building in, your foundation will require excavation of earth to the foundation sub-grade (a minimum depth required by code or to undisturbed soil with adequate bearing capacity). In cases where the soil bearing capacity is inadequate or suspect, a geotechnical or soils engineer may be needed to determine the actual bearing capacity of your soil. This information is essential for the structural design of the foundation to support your home or addition. It will also generate the specifics of how deep and how wide the footings will need to be which is a primary factor for excavation contractors to determine the amount of time required to dig your foundation and how much soil may need to be stockpiled and hauled away. You'd be amazed how quickly a job site can be overtaken by excess earth that has been dug up. Soil expands approximately 30% once its excavated so what would fill ten trucks in the ground will require thirteen truckloads to haul away. The excavation category is where the scope of work for site preparation (storm run-off protection, silt fence, construction entrance etc.), drainage, backfill and rough grading are identified, evaluated and amounts for the work determined. Final landscaping is often looked at under this category, although it can also be looked at under Specialties. Does your project require a simple perimeter footing only 24" below grade on a flat lot? or does your project call for an eight-foot-deep excavation, hauling excess earth away, blue rock demolition and removal, major old tree trunk root base removal, and installing a subsurface drain system? Is there an underground stream or lava tubes under your lot? All these issues and more come into play when evaluating your project scope of work and determining the right amount of funds necessary to accomplish the task. Like the Phases discussed previously, Excavation has numerous variables that will be site specific to your home and must be thoroughly evaluated to determine the right price for the work required for your project.

Concrete is a separate Phase on our Construction Process List because of the numerous parts of construction concrete is used for. This phase is where concrete footings, steel reinforcement of footings, concrete walls, concrete slabs (on grade and suspended) are evaluated and analyzed for pricing. The home site will have a major impact on concrete pricing. Some sites require special concrete pump trucks to pump concrete to sections of the building site where trucks cannot unload, or men with wheelbarrows are not able to access. Concrete work is done at different times during the building process and each time will require different set up depending upon what is being done and the access to the work area. Concrete patios, walkways and driveways are generally done after the building or addition structure is built and the project is in the finishing stages. There are many different finishes available for concrete today and special patterns, textures, colors and additives are used for enhanced finish appearance. Naturally, each special finish has its own unique requirements and investment amount to accomplish. Concrete is also used as a countertop material but we generally price that work with the Cabinetry & Counters Phase. You are probably tired of reading that this item pricing will vary depending on your homes specific site conditions and your finish selections for exposed concrete, but it is true for the Concrete Phase as well. Please note that the examples I note are not exhaustive, they are intended to help you, the reader, understand some of the various ways that Concrete might be used on your home.

Masonry is the Construction Phase that encompasses masonry foundation and retaining walls, brick work, stonework, fireplaces and chimneys, brick and stone patios, pavers as well as patchwork and/or repair of existing masonry surfaces. Sometimes masonry foundation walls are used instead of poured concrete walls.

Stucco is often applied as a finish over masonry walls. Masonry work in general is very durable and when done correctly, will last a very long time (examples abound in Europe of 500 plus year old masonry castles and homes). Cost benefit analysis of masonry construction really supports the premise that you get what you pay for!

Each type of masonry has different pricing and different specialty contractors so it's important to be specific what type of masonry might be used on your project and obtain specific pricing from the appropriate specialty masonry contractor. (Some masons will only install CMU block and brick, some only install stone, some only do flat work etc). In some parts of the US there are few skilled stonemasons (which is part art and part construction – look closely at stonework around your town and you'll see what I mean) and it is very important to find tradesmen with the skill and experience in the trade to be able to execute their craft beautifully. Brick and stone masonry walls can be built as integral with CMU or can be installed as veneer in front of CMU or wood or steel frame walls. Each approach will have different pricing, so again, the specifics relevant to your project must be spelled out for an accurate price to be calculated.

The next phases on the Construction Phase list are Floor Framing, Wall Framing and Roof Framing. The framing requirements for your project will vary depending upon the size and design of your project. There are many different framing materials used; dimensional lumber, engineered floor trusses, special floor sheathing plywood, wood studs of various sizes, engineered beams, steel posts and beams, roof rafters or roof truss systems and numerous wall sheathing and roof sheathing products. Lumber prices fluctuate quite a lot, and your project will need to be priced out using current lumber prices. Occasionally weather events or other factors cause spikes in lumber prices which may effect your projects lumber pricing. Your framing investment amount will vary depending on lumber prices in your area and the complicatedness of the structure. Homes with a lot of corners and jogs, angles or curves and complex roof design will cost substantially more to frame due the complexity of the design than a simple rectangle shaped home. The more architectural complexity in the shape and exterior cornice and trim the higher will be the amount to frame. Once again, the pricing will be based on the design, so the preliminary design elevations and plans are used to provide adequate information for a professional to project an accurate preliminary rough budget estimate for the work. It'll be a lot closer than the "ballpark" number that nobody will hold anybody to – but often that's the number the Owner thinks is going to be the final number (the truth is that the "ballpark" number is usually worthless, and possibly dangerous – like building your house on sand – building your budget on a guess). See Blog Post Article "Inflation Pressures Building & Remodeling Industry" for more information.

The next phases of the Construction Phase Process are Roofing & Gutters, Exterior Trim & Decks and Siding. Each one of these Phases deserves a chapter in a book by itself but I don't think this is the right place to go into that level of detail for these Phases. Roofing prices will vary greatly depending upon the type of roofing selected, the pitch of the roof and the complexity of the roof design. A steep roof with many intersecting slopes and dormers with Vermont Slate and copper flashings will be very expensive. A moderate slope roof with a composite roof shingle and aluminum flashings will be much less expensive. A prefinished aluminum standing seam roof will be somewhere between the two. Copper gutters are significantly more expensive than aluminum gutters. Historical replicas of round gutters are more expensive than "ogee" shaped gutters. Custom shop made box gutters must be special priced. Exterior trim and decks cover a wide multitude of details and materials. Specifics must be determined to price these out correctly. Siding varies greatly as well. On the lower end of the range is vinyl siding, then material quality improves with fiber cement siding, and continues up to wood siding (beveled siding, shingles, board and batten) in different wood species (pine, cedar, redwood etc). Each selection and style of siding has different pricing based on the material pricing and the labor to install. It's important to note that roofing and siding performance is dependent on proper flashing details at the intersections (valleys, windows, doors, corners, terminations, vent penetrations etc.) and correct installation of the roofing and siding is of utmost importance. Many workers are not properly trained in these details and many water intrusions occur from poor workmanship in these phases. Like everything in life, there are different levels of quality, and roofers and siding tradespeople have different levels of skill. Well experienced, skilled tradespeople are very important for the quality of your new home and for its durability. It matters not what the price or type of the roof material or siding material is if it's not correctly installed. The same formula applies to these phases: specify, quantify, and price out by skilled trades to develop an accurate construction budget.

Doors and Windows are the next two Phases on the Construction Phase List. You've probably checked out some of the options already. What category or class of product makes the most sense for your project? Some of your choices are vinyl windows and doors, aluminum, wood, aluminum clad wood, fiberglass, or composite. Some manufacturers will make a custom sized unit with a custom color aluminum clad exterior and a custom wood clad interior – these units are finely crafted works of art. Other companies make composite, fiberglass or vinyl windows with an automated mass production process. Where in the spectrum do your windows fit? Types of glass vary and can be selected for standard performance (low e insulated glass) to very high performance (which varies depending on your homes site climate zone and the orientation of the window (N,S,E,W)). Not all manufacturers offer every option so you'll need to narrow your search early in your planning process. Each choice has a specific price for it. Type of windows and doors will effect your budget as well. Windows come in fixed units, awning, casement, double hung, single hung, cottage style, sliding, and specialty shapes as well as custom sizes. There are snap in grilles, simulated divided light grids and true divided light mullions available. Doors offer too many options to mention here, but from a simple flush door with a standard lock and deadbolt to a multi slide pocket door system with three point locks and hurricane resistant rating the range of type of door, quality of door and options available is tremendous. Prices vary just as greatly as the choices. The same principle applies to the installation of doors and windows as to roofing and siding. Proper installation is often overlooked and underestimated. Incorrect installation will lead to premature failure of the door or window, possibly a water intrusion which may result in rot in the walls or a mold infestation. Proper installation is essential for durability and your comfort. This is a service and skilled tradesman issue which must be accounted for. Incorrect installation will void many window and door manufacturers warrantees, so this issue must be thoroughly planned and budgeted for. Interior doors must be specified as well. Style of door (swing door, double swing, pocket, sliding) as well as

Type of door (paint grade, louvred, special wood, panel door etc.) as well as size of door will all effect the interior door pricing. Door hardware can vary widely as well.

You must decide what level of quality and performance are best for your project, make sure your builder or remodeler has the proper skills to install the units properly and then the Windows & Doors Phase can be evaluated.

Next up on the list is Plumbing. Simple, right? I just need the new bathrooms hooked up to water and a drain. There is a laundry room right next to where the new addition master bathroom will be. Seems like a slam dunk! It shouldn't cost too much to do that right? Well, let's examine that thought. We have a pretty good idea of what the plumbing will cost for the new piping for the new bathroom based on the water, drain and vent pipes we need to connect to being adjacent to where the new plumbing will go but let's verify. Site inspection with our plumber (standard practice we perform in our project feasibility study research) reveals that the water service into the house is an old ¾" galvanized pipe and is undersized for the existing house with the new bathroom. It is near the end of its useful life and must be replaced anyway, so there is a deferred maintenance infrastructure type upgrade that must be done. That'll require digging up the yard and connecting a new water service line from the local water supply at the street to the home. The site visit also uncovers the fact that the existing gas HW heater is too small and is not vented correctly. A new high efficiency unit is needed. Finally, the laundry drain is too small to connect a toilet waste line to and we must drop a new drain down into the basement and connect to it. This will require some walls to be opened and then patched back to previous condition. All this work must be done to accomplish the new bathroom. Obviously, this will affect the overall plumbing phase installation amount. Plumbing fixtures vary from budget economy fixtures (we will not install these since they fail quickly) to super luxury with a good number of reasonable choices in the middle and upper middle quality range. As owner you must select your fixtures and fittings, then accurate pricing can be done. 

Mechanical and Electrical are the next two phases to be evaluated. The scope of work in each of these phases can be minimal: relocate a switch and plug and extend a couple floor HVAC registers, to extensive: a new HVAC system and electrical rewire with new service and panel). We inspect the current conditions with the appropriate trade contractors and based on your requirements and features desired develop your scope of work and budget accordingly. This is not a phase to "ballpark guesstimate" – there are too many variables that might be easily overlooked and will cause issues, delays and cost over runs later. 

Insulation, Drywall, Ceiling Coverings, Millwork & Trim, Cabinetry & Counter tops, Specialties, Floor Coverings and Painting are all very important phases that also must be carefully planned and budgeted for. These phases, along with plumbing and electrical fixtures, are generally where owners spend the most time looking at their options and checking out various materials and finishes. Sometimes the choices are overwhelming, and owners have difficulty making some of these selections. Professional assistance is available for interior design selections and depending upon your comfort level making choices, style and budget there are various levels of design consultants available to assist with this task. These decisions are very important for the overall schedule and integration of the project, since different fixtures and finishes require different preparation of the structure and system rough ins. Proper planning takes these factors into consideration and the work is done such that when it's time to install the finishes everything goes together smoothly, with minimum adjustments and delays.

Every detail must be planned out carefully and executed meticulously to accomplish the desired finished product. This thoroughness of planning and careful execution has proven to result in projects completed on time, on budget and with a minimum of surprises.

For all major additions and renovation projects we prepare an outline of the relevant phases involved to develop a realistic preliminary rough budget and timeline for the project. This gives the owner valuable budgeting information to determine if it makes sense for them to invest in our Preliminary Design & Feasibility Study and proceed with the first steps of design concept development and scope of work.

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