Room Addition Cost (Design Guide)

Here we discuss room addition cost including how to calculate what you’ll pay for materials, labor and for each type of room plan.
Building a room addition is a great way to get yourself some additional living space and add additional resale value to your home. A room addition is basically an extra structure that you build onto your existing home.

Depending on the type of room you want to add, building a room addition may be less expensive and less stressful then moving in to a new house. In addition, with a brand new room addition you can get a space that fits your exact needs and specifications.

How to Calculate Room Addition Cost

When you are planning a room addition, you need to be aware of the following things that can affect the cost. The main costs will be labor and material, but you also need to be aware of the cost of permits. The cost of permits can vary according to where you are located.

Another big thing to think about it they type of materials that you will be used, this can increase or decrease the total cost of your room addition.

There are also some ways that you can save on labor costs. While DIY might cost less, hiring certain experts such as plumbers and electricians will keep you for making costly mistakes.

Room Addition Cost Per Square Foot

In the United States, the national averages for the cost of an addition will be from around $80 -200 per square foot. This is for a ground floor addition.

If you are looking to build a second- story addition the cost will increase as these are more difficult and complex to build. A second story room addition will cost from $100 to $300 a square foot.

Room Addition Cost Breakdown

Room addition with vaulted ceiling design

The first step you need to take in building your room addition is to secure the necessary building permits. Depending on where you are, permits could cost your $100- 300 each.

The next step would be to prepare the building site. This could include excavation and demolition. This stage should cost about $1,500 to 3,000.

Next would be laying the foundation, this should cost about $4-8 for every square foot.

Here are the rest of the general elements of a room addition and their respective costs. Again, remember that the cost can either increase or decrease depending on the material used and whether you DIY or hire an expert:

• Roofing: $7-10 per square foot
• Siding – $8 per square foot
• Insulation – $2-3 per square foot
• Drywall – $2 per square foot
• Flooring – $2-4 per square foot
• Windows – $400-800 per square foot
• Crown molding – $7 -16 per linear foot
• Plumbing – $450 – $1,800 per fixture
• Electrical – $2 to 4 per square foot
• HVAC & Ducting – $800 to 1,600
• Landscaping – $500 – $2,500
• Clean up – $500- $1,000

If you are building a small basic room, you might want to skip on hiring an architect. But if you’re planning a big room with a lot of fixtures and features, you should consider having an architect draw up your building plans. This could cost you about $2,000- $5,000.

Material Cost For Room Addition

As we mentioned before, the type of material will have an effect on the cost of your room addition.

One tip we can give you to save on the cost of building materials is to take the dimensions of the building materials into consideration. Every bit of material that you need to add or cut will affect the cost.

For example, most two-by-fours come in lengths of 8 feet; this means that you can maximize the use of the material by building a room with dimensions in multiples of 8. Doing this saves you money because you don’t have to cut or add material.

Labor Cost

Hiring a contractor will up your room addition cost. Labor costs will come to around 30-50 percent of your total budget for your room addition.

Doing things yourself, or even partially yourself could save you some money. For example, if you do your own demolition you could save $500 in labor costs. However, some of the more complex operations, like installing plumbing or electrical wiring might be better off left to the professionals.

Average Cost of Room Addition

Ultimately, the average cost of a room addition depends on the type and size of the addition.

12×12 Room Addition Cost

The average cost to add a 12 foot by 12 foot room to your home will come to around $11,520 – $28,800

12×12 Room Addition Cost DIY

If you decide to do it yourself, you should subtract the labor cost from your budget. If we say that labor costs are 30% of your budget, DIY-ing should cost around $8,064 – $20,160.

20×20 Room Addition Cost

If you want to add a 20 foot by 20 foot room to your home, be prepared to spend from around $32,000 to $80,000.

20×20 Room Addition Cost DIY

If you decide to DIY, subtract the labor cost from your total budget. If we place the labor cost at 30% of the budget, DIY-in should cost around $22,400 – $56,000

Bathroom Addition Cost

Remodeling part of your existing structure to become a bathroom can cost a minimum of $5000. To add a bathroom addition to your home will cost at least $50,000.

The U.S average for a bathroom add-on is $75.000. The cost will vary substantially based on the state you reside in and their permitting process as well as local labor costs and the materials you choose. To create your own plan there is bathroom remodel software to help.

Family Room Addition Cost

The cost of a family or living room addition will depend on the size of the room you want. An average size for a living room is about 18 by 12 feet and that will cost around $17,300 to $43,200.

The fixtures that you want will also increase the price so keep that in mind when thinking about cabinets, lights, and even molding. For living room remodel ideas visit this page.

Laundry Room Addition Cost

Building the room itself will only cost about $2,000 to $10,000 depending on the size and the material that you use.

What can really up the price would be the fixtures such as plumbing, appliances, and even storage space. With that in mind the average cost to add a laundry room should be $5000.

Mudroom Addition Cost

The mudroom addition cost runs between $100 to $200 per square foot if you are building in an existing interior space.

If you’re building from the ground up the price will be much higher and can cost anywhere from $100 to $500 per square foot depending on local building codes, materials and labor costs.

Mobile Home Room Addition Cost

Take note that, when you’re building a mobile home addition, the new room cannot be attached to the mobile home. The mobile home might not be able to support the weight of an addition.

These are the most common types of mobile home room additions and their average cost:

• Barn or shed – $1,700 – $5,000
• Carport (metal) – $2,150 – $4,800
• Deck – $4,000 – $11,000
• Porch – $4,600 – $10,500
• Detached garage – $4,600 – $10.500

Prefab Room Additions Cost

A prefab or modular home is basically a structure that you can erect out of parts or pieces that are prebuilt. You buy a modular home or room and the parts are shipped to you and you or your contractor just has to put it together in your property.

You can also get prefab room additions. The most common types of modular room additions and their average costs are as follows:

• Shed – $3,000
• Deck – $7,500
• Basement – $18,000 to $30,000
• Two-car garage: $27,000

Cost of Three Season Room Addition

If you want to add a three-season room to your home, it will cost your around $9,000 to $40,000. Most of the cost will come from material prices for which you should budget around $5,000 to $30,000.

Labor costs for a three season room addition will come to around $9,000 – $40,000.

To help visualize your room addition plans you can use one of the many home design software programs available.