Home Addition Cost Guide

By PropertyClub Team
Jul 27th 2023
It's common to want to expand your house to create more living space, but a home addition can cost a lot, with prices starting at $15,000 for a basic home addition to over $100,000 for something larger and more luxurious. There are different price points to expect based on what kind of home additions you want to make. 

hash-markHow Much Does the Average Home Addition Cost? 

The average home addition will cost around $125 per square foot or around $50,000 for a 400-square foot home addition. Of course, having a home improvement project will always have its own little variances in price, depending on where you live, who you contract out to do the work, as well as the style of housing you're trying to get. However, there are general guidelines that you can rely on if you're looking to do a more common type of expansion. Here's what you need to know.

hash-markCommon House Addition Costs

  1. 20x20 Room Addition Cost
  2. Building an Apartment Over a Garage Cost
  3. In-law Apartment Home Extension Cost
  4. Building a Sunroom Cost

1. 20x20 Room Addition Cost

Most major room additions are meant to be larger than your typical bedroom, and rightfully so. It's a significant endeavor, so you don't want to have to do this process more than once. A 20x20 foot room addition costs anywhere from $80 to $200 per square foot. 

This means that a basic room will cost around $30,000 to $80,000 in most cases. In some situations, you might be able to get it done for as little as $16,000. However, this is the exception rather than the rule. 

2. Building an Apartment Over a Garage Cost

Garage apartments, or even just garage room add-ons, remain strikingly popular as a "build up" type of extension. The cost of additions over garage roofs can vary based on the structure of your roof, as well as the size and functionality of the addition that you want to make. Here's what you need to know:

  • A bonus room over a garage costs between $170 to $220 per square foot. This includes the price you'll pay for electricity, air conditioning, and other amenities. This can lead to a price tag around $60,000 to $85,000 depending on the size of the room.
  • A full-blown apartment will cost around $170,000 on average for a 24 square foot garage. This includes the price of all the utilities that are needed in a standard studio apartment—like electricity, plumbing, and gas for a kitchen stove. The home addition cost per square foot can vary greatly depending on what fixtures you choose. 
  • If you want just to add a standalone garage to your property, expect to pay an average of $26,000. This low price tag is to be expected since you probably won't need climate control or plumbing. 
  • A detached, simple garage can cost as little as $15,000 to create. This price tag involves a building that doesn't involve any form of electricity or plumbing.
  • Additional repairs and structural assistance may be needed. If your garage is older, you may need additional structural supports to make this project doable. 

3. In-law Apartment Home Extension Cost 

An in-law house is a smaller, mini-apartment that is often made as a standalone building on a person's main property. Originally designed as a way to make multigenerational living easier while still offering privacy, in-laws are now used as guest houses as well as private houses for young adult renters. 

A typical in-law will include a small bedroom, a bathroom, a kitchenette, and a small living space. However, the definition of an in-law suite can vary from place to place. If you are just looking for a simple bedroom addition, you can usually get it for $44,000. 

On the other hand, if you choose to have a completely standalone project, then you should expect to pay well over $100,000. In some cases, the price of a luxurious in-law apartment can cost as much as a standard house!

4. Building a Sunroom Cost

Sunrooms, also known as Florida rooms, are a great way to enjoy the outdoors without full exposure to the elements. These additions are smaller than a typical garage apartment and don't always require as many amenities. As a result, they're relatively affordable.

If you want to build a sunroom, expect to pay around $20,000 to $70,000 for a 10x20-foot space. This is, of course, assuming that you're building it from the ground up. Prefabricated sunroom kits are available, and they cut costs well. If you choose a kit model, you will pay around $11,000 on average.

hash-markHouse Addition Cost Considerations

Every home addition has a myriad of different issues that you will need to take into account when you put together a budget. When you're compiling your budget, make sure to keep these major factors in mind:

  • Design: Every addition will cost money to design. Depending on the type of add-on you want and the architect you hire, this will cost anywhere between $2,000 and $8,000. Certain styles, such as mid-century modern, can also increase the price of the design you get.
  • Materials: This is an umbrella term that covers a LOT of different supplies. For example, insulation ($2 per square foot), roofing ($80 to $600 per square foot), flooring ($10 or more per square foot), and more. 
  • Labor: Unless you are a licensed contractor, you will need to get the overall estimate of labor for installation, site prep, and cleanup. Specialists can cost around $100 per hour, while regular laborers may be slightly less.
  • Doors, Windows, and Utilities: Installing these will require specialists, as well as the proper materials. Each specialist will have their own rates. For example, you can expect to pay an electrician 100 dollars per hour.
  • Permits: Though the actual material and labor costs of the building addition are going to be your biggest issue, the price of permits and certifications can be a pain, too. Depending on what you're building and where, you can expect to pay as little as $150 to upwards of $600.

hash-markHow Do You Keep Your Costs Low? 

This is often the biggest question that homeowners have when they are trying to put together a budget. Truth be told there are a couple of smart tips you can use to make the most of your spending:

  • Shop around for both materials and labor. The more quotes you get, the better off you'll be. Overcharging companies are not as rare as you hope they would be, and it's important to know what the average price is.
  • Prioritizing matters. Yes, you might have wanted those swanky hardwood floors, but can you really afford them? If you are on a strict budget, be honest about it. Though you might not get exactly what you want, you can still have a relatively luxe home addition. 
  • Don't always go for the cheapest contractor. Cheap contractors, particularly those that have bad reviews, are cheap for a reason. The reason is that you may have to pay another contractor to fix their mistake—or worse, the quote they initially give you won't be the full story. Research your contractors, and approach low-end ones with caution. 
  • Ask what each estimate you get covers. You'd be shocked at how many "complete estimates" don't include minor fees and taxes. This can lead to a massive underestimate of your actual costs. To prevent it, ask for everything and ask if there are any additional fees that you may incur during your build. 
  • Before hiring a contract, list out your expectations and budget in a written agreement. Be succinct here! By outlining your expectations in a legally-binding contract, you make it possible to address hiccups in the plan quickly and cost-efficiently. 

hash-markHome Addition Cost Bottom Line

If you are looking to add a new room (or building) to your current home, you have a lot of money that you'll need to save up for. Even if you're just putting together a bare-bones shed, you will need to spend a minimum of $15,000 to see it come to fruition. If you want to go for a luxury in-law suite, the price can easily reach the six-figure benchmark. 

The bottom line is that making these renovations are will cost a lot of money and that it's in your best interest to keep your costs low. With savvy shopping and a lot of questions, your home addition costs should be manageable.