How much does it cost to build a guest house?
Ashburn, VA

How much does it cost to build a guest house?

Ashburn, VA

How much does it cost to build a guest house?

$150 – $250per square foot (custom-built)
$90,000 – $150,000total cost (600 SF)

Get free estimates for your project or view our cost guide below:

$150 – $250 per square foot (custom-built)

$90,000 – $150,000 total cost (600 SF)


Get free estimates for your project or view our cost guide below:
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Tamatha Hazen
Written by
Tamatha Hazen
Edited by
Tara Farmer
Fact-checked by
Tom Grupa

Average guest house cost

The average cost to build a guest house is $90,000 to $150,000 total for a custom-built structure, depending on the size and features. A backyard guest house costs $48,000 to $96,000 for a prefab unit with installation. Building a guest house by converting an existing garage or shed costs $12,000 to $120,000.

Average guest house cost
Guest house size Average installed cost
(custom-built)
Average installed cost
(modular)
400 SF (studio) $60,000 – $100,000 $32,000 – $64,000
600 SF (1-bedroom) $90,000 – $150,000 $48,000 – $96,000
800 SF (2-bedroom) $120,000 – $200,000 $64,000 – $128,000
1,000 SF (2-bedroom) $150,000 – $250,000 $80,000 – $160,000
1,250 SF (3-bedroom) $187,500 – $312,500 $100,000 – $200,000
1,500 SF (3 beds + flex) $225,000 – $375,000 $120,000 – $240,000

Cost data is from research and project costs reported by HomeGuide members.

Get free estimates from adu contractors near you.

Guest house cost by type

Building a guest house costs $20 to $250 per square foot, depending on the type. A custom-built guest house is the costliest and most customizable option. A modular guest house is faster and cheaper but offers fewer choices. Converting an existing structure is the cheapest way to add guest quarters.

Guest house cost by type
Guest house type Average cost per SF Average total cost (600 SF)
Custom-built guest house $150 – $250 $90,000 – $150,000
Modular guest house $80 – $160 $48,000 – $96,000
Convert existing structure $20 – $200 $12,000 – $120,000

A luxury guest house with columns and a large patio.
A luxury guest house with columns and a large patio.

Custom-built guest house

Building a house costs $150 to $250 per square foot and goes as high as $400 per square foot or more for high-end finishes. You'll spend the same amount building a guest house from scratch since you are basically building a new house on a smaller scale.

Ready-made guest house

A ready-made, or modular guest house costs $80 to $160 per square foot installed for the prefabricated structure. This budget-friendly option is also much faster than a custom build, giving you a finished guest house in about 1 to 4 months.

Depending on the zoning in your area, you can choose from several ready-made options in addition to a standard modular guest house or accessory dwelling unit (ADU). Prefab tiny homes, container homes, and even prefab log cabins can serve as comfortable guest houses.

Ready-made guest house costs
Prefab unit type Average cost per SF installed Average installed cost
(600 SF)
Modular guest house $80 – $160 $48,000 – $96,000
Accessory Dwelling Unit (ADU) $90 – $160 $54,000 – $96,000
Prefab tiny home $150 – $250 $90,000 – $150,000
Container guest house $120 – $300 $72,000 – $180,000
Prefab concrete guest home $110 – $180 $72,000 – $108,000
Modular and prefab log cabin $100 – $250 $60,000 – $150,000

A small green ADU and guest house in a home's backyard with a flagstone pathway
A small green ADU and guest house in a home's backyard with a flagstone pathway

Modular guest house

A modular guest house costs $80 to $160 per square foot for a fully installed detached structure. Units with a full kitchen and bath have the highest costs. Modular units without kitchen or bath facilities are cheaper but require guests to use the facilities in the main house.

A modular guest house is set on a foundation, separate from the main house, and is composed of several components that are assembled on-site. The components include the walls, doors, windows, electrical outlets, and plumbing.

Accessory Dwelling Unit

An Accessory Dwelling Unit, or ADU costs $90 to $160 per square foot installed. Different than a guest house, an ADU is designed for long-term use and must have a kitchen and bathroom.

Unlike a modular guest house, a modular ADU is not always a separate structure but can be a connected dwelling. A modular home addition costs $90 to $210 per square foot, including the costs to prepare the site and pour a foundation.

Prefab tiny home

A prefab tiny home costs $150 to $250 per square foot installed for a small house less than 400 square feet. Sometimes called a studio shed, these small units often come complete with basic amenities including a kitchen, bathroom, living area, and sleeping space.

A prefab tiny home guest house or ADU
A prefab tiny home guest house or ADU

Container guest house

A prefab shipping container guest house costs $120 to $300 per square foot installed. Container homes are gaining popularity for residential use because they are cost-effective and easy to build. Container homes are also eco-friendly since they reuse and recycle materials that would otherwise be dumped.

Prefab concrete guest house

A prefab concrete home costs $110 to $180 per square foot, depending on the finish level of this modern-looking home. Factory-built panels are easier and faster to install than poured concrete.

Modular log home

A prefab log cabin home costs $100 to $250 per square foot, including materials, installation, interior, and exterior finishing costs. Modular log homes are delivered in one or two fully finished pieces.

Existing structure conversion

Converting an existing garage, shed, or barn to a guest house costs $20 to $200 per square foot. In addition to saving time and money, there are fewer zoning issues to deal with when converting an existing structure.

Existing structure conversion costs
Structure Average installed price
per SF
Average installed cost
(600 SF)
Garage conversion $50 – $200 $30,000 – $120,000
Metal building guest house $25 – $80 $15,000 – $48,000
Pole Barn guest house $20 – $60 $12,000 – $36,000

Garage conversion

Converting a garage costs $50 to $200 per square foot to turn an existing garage into a functional living space. The conversion takes 4 to 8+ weeks to add new floors, walls, windows, insulation, drywall, electrical, plumbing, and HVAC.

Metal building guest house

A metal building guest house conversion costs $25 to $80 per square foot to create a finished living space inside an existing metal shed or building. Some neighborhoods restrict new metal buildings, but if you have an old shed that was grandfathered in, converting the space is a great option.

Pole Barn guest house

A pole barn guest house conversion costs $20 to $60 per square foot to finish the interior living space of an existing pole barn structure. Pole barns are more common in rural properties and make a great additional living space for guests.

Guest house cost factors

Factors that influence the cost of building a guest house include:

  • Size –The larger your guest house, the more it costs to build.

  • Zoning – Zoning laws dictate the square footage, the number of guests and parking spots permitted, and the distance between the main house and the guest house.

  • Permits Building permits cost $500 to $2,000 for home construction. Your contractor or builder typically handles the permitting process.

  • Financing – Building a guest house is costly and may require financing, which impacts the total cost. Loan options include construction loans, a home equity line of credit, and mortgage refinancing.

A garage converted into a living room.
A garage converted into a living room.

Planning & site prep

More than just the building itself, other costs associated with guest house construction include:

Features

The more features you add to your guest house, the more it will cost. Building a small studio with no plumbing for overnight guests is an inexpensive option. Including a kitchenette and half-bath costs more but adds convenience and comfort for guests that stay longer.

Guest house feature costs
Feature Average installed cost Details
Kitchenette $5,000 – $20,000 Small version of a kitchen with a sink, microwave, and small refrigerator.
Full kitchen $25,000 – $45,000 Regular kitchen with full-sized appliances including a refrigerator, stovetop, and oven.
Half-bath $4,500 – $8,000 Toilet and sink only
Full bath $18,000 – $47,000 Toilet, sink, and a shower/tub combo

  • A matching set of kitchen appliances costs $2,500 to $6,800 on average with installation for a refrigerator, microwave, range, and dishwasher.

  • The labor alone for individual appliance installation is $100 to $350 per appliance.

A small kitchenette in a guest house or mother-in-law suite.
A small kitchenette in a guest house or mother-in-law suite.

Guest house pros and cons

Building a guest house is a big commitment of time and finances, but there are many advantages to having the additional living space. Still, the building process can be intimidating and disruptive to everyday life. Consider the pros and cons of building a guest house before committing.

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Guest house pros and cons
Pros Cons
  • Quiet space for work or hobbies
  • Private quarters for guests
  • Space for older parents or adult children
  • Additional entertaining space
  • Potential rental income
  • Increased property value
  • Expensive project
  • Takes careful planning and permitting
  • Interrupts daily life for an extended period
  • May take longer and cost more than planned

Guest house FAQs

Can I build a guest house on my property?

Before you hire a contractor or start drawing up blueprints, confirm that your neighborhood allows you to build a guest house on your property. Check with the local municipality and your HOA, if applicable, to see what zoning restrictions exist in your area.

Do I need a permit to build a guest house?

Yes, almost every construction project involving a foundation requires a building permit. In some areas, a small structure less than 100 square feet won't require permitting but check with your local building department to confirm what setback or zoning restrictions apply.

How long does it take to build a guest house?

Building a guest house from scratch takes 4 months to a year, plus the time for planning and permitting. A modular unit is much faster to install, taking 1 to 4 months for delivery and installation.

Does a guest house increase my home value?

Yes, in most cases a detached guest house will increase the value of your home, especially a guest house with a bathroom, kitchen, and laundry facilities. An attached guest house adds to the square footage of your home and always increases the value.

Can I rent out my guest house?

Depending on where you live, you may be able to rent out your guest house, but there are a few things you need to do first:

  • Check your local zoning laws and regulations on whether short-term or long-term rentals are permitted.

  • Meet all applicable safety and health codes, such as fire and building codes.

  • Get liability insurance to protect you in case something happens to your guest while they are living on your property.

  • Set up a rental agreement to protect you and your guests in case of any issues. The agreement should include the rent amount, length of stay, and the terms of cancellation.

Getting estimates from a guest house builder

If you're thinking about building a guest house, first check to see if your neighborhood allows it. Then, follow these recommendations to find the best ADU contractors for your project:

  • Decide whether a custom-built or modular guest house is best for your needs and budget.

  • Get at least three estimates with the same guest house size and type to compare.

  • Read reviews HomeGuide and Google and ask to visit a job site to see the work in progress.

  • Pick a contractor familiar with guest house construction.

  • Request a full itemized contract in writing in case of disputes.

  • Ask your builder about their preferred lenders for easier financing.

  • Avoid making large deposits up front. Never pay in full or in cash.

Questions to ask your builder

Ask these questions to narrow down the list of potential guest house builders:

  • How long have you been in the home building business?

  • How many guest houses have you built in the last year?

  • Do you have designers to help me create a floor plan?

  • Can you provide me with a list of references and contact details?

  • Can I see your portfolio of completed guest houses?

  • Can you give me the addresses of the homes you have in progress?

  • Are you licensed, insured, and bonded?

  • How do you handle damage that happens on the job?

  • Who will serve as my project manager, and will you use subcontractors?

  • What qualities do you look for in your subcontractors?

  • What hours will you and your crew work on-site?

  • How long will the guest house construction take?