Roof Dormers & Extensions: The Definitive Guide for Long Island (2020)

Long Island Dormers Guide
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If you are looking to add more living space, functionality, and property value to your home by adding a dormer roof(s) but don’t know where to start? 

You may be thinking to yourself…what is a dormer roof? What is the cost of adding a dormer? How do I add one to an already existing roof? You’re in the right place!

What started as a simple architectural trend for homes in 16th Century Britain, dormers are still utilized today to add character, depth and most importantly extra space, light, and ventilation to a home. Looking to add a dormer to your Long Island home? Keep reading!

LIMITED TIME OFFER: Save $1,997 with A Father of Four’s Dormer Discount!
Teachers, Police, and Military Discount available! Take up to an extra 10% OFF your project.

But, what is a dormer? I’m glad you asked! 

A dormer is added to the sloped part of a roof to add a ton of natural light, ventilation and space to an attic, loft, or any other room with a vaulted ceiling. Dormers take a room with limited livable space and functionality into a transformed, useable room.

Simply explained, a dormer is a second story addition or a roof structure, typically containing a window that projects vertically from the slope of a roof. Dormers are typically the primary element of any home loft or attic conversion. The most popular home roof conversion is the addition of a flat roof dormer.

Fun fact: Dormers were first seen in the 12th century when they were added to the spires of churches to add more ventilation due to how hot these higher levels were in the summer months. The first dormer window being the lucarne dormer, which is a very slender dormer. The earliest example of this can still be seen today on the spires of the Cathedral in Oxford.

Why Should You Add a Dormer to Your Home?

  1. Added Space
  2. Increase Property Value
  3. Visual Appeal

The added space! The biggest benefit you receive by adding a dormer to your home is the added space you are given. They allow you to add space to your home by building up, not out.

Adding a dormer to your home can transform the upper level of your home immensely or create a new level entirely! Most upper levels, like lofts and attics have drastically  vaulted ceilings, making their use and functionality extremely limited.

Have you ever gone into a second story room and had to duck down a quarter of the way into the room? With a dormer there is no need! Dormers allow you to get so much more use out of the space in your home than you would have without them. If you can relate to this, ask us about a true-reverse dormer.

What comes with additional space in your home? Increased property value!

Adding a dormer roof to your home will bring up the value of your home because of how much square footage you are adding to the home!

Another benefit of adding a dormer to your home is the visual appeal.

Many add them to their homes simply because they love the appearance and look a dormer brings to a home.

What if you’re interested in adding a dormer to your home, but live in a one story home.

You can create a pseudo second story to your home by adding a dormer roof!

Build a Second Story Addition To Your Home

Mother Daughter Extension

There’s a lot of confusion about this and we’re here to make this as easy as possible for you. Dormers can also serve as a second story to your home.

This is called a true-reverse second story addition. Basically, you can add a completely new story to your home. Check out the image above.

This was one of our own job sites of a single-story home, and we added a true-reverse dormer in the middle, and extended it into an entire second story.

This is yet another way you can add a dormer to your home!

How Long Would a Dormer Roof Conversion take?

3 – 4 Months

The average time frame when building a dormer onto your home is 3-4 months, but depending on the project and size of the dormer this may vary a bit.

All dormer conversions have something in common, the three stages of the conversion; designing, planning, building.

What is the Process of Adding a Dormer Roof to My Home?

The first step of adding a dormer to your home is to speak with a licensed contractor and draw up plans. There are many things to consider when adding a dormer such as access, accommodation needs, headroom and fire access. After completing the design, you then must make sure you meet all legal requirements and obtain any permits needed, if necessary (more on that later).

Second, is properly planning your home extension. Adding any kind of extension, additional or remodeling to your home without the correct permits is illegal and can result in up to $15,000 in fines! Get your necessary permits here: Permit Applications

A dormer conversion could take as little as 4 weeks but plan for the project to take a total of 3-4 months, depending on the overall size of the conversion.

Lastly, starting your dormer roof construction!

The process is as follows..first the roof and exterior framework will be built.

After the framework has been completed, the newly added room will be connected to the rest of the home where necessary and if it does not exist already, staircase access to the addition will be added. 

After these technical steps, the dormer will be cosmetically finished on both the interior and exterior.

Types of Dormers

There are many types of dormer roofs you can add to your home! As long as you choose to work with a professional, like A Father of Four, your new dormer will match the style of your home flawlessly.

The most common type of dormer designs are..

Gable Dormers

Gable Dormers

Gabled dormers have a triangular roof with a peak at the top, sloping downward to jut up and away from the dormer window just a bit. They are often referred to as the dog house dormer because they are of similar design. Gable dormer designs are ideal when wanting some shade over the windows and in your room and are the most popular dormer style used on homes today. 

Gable dormers design are probably the most well known when one thinks of dormers and adding a dormer to their home. 

Depending on the size and complexity, a gabled dormer could range from $4,000 to $11,500. 

Dormers and gables, oh my!

Cost Range: $4,000 to $11,500

Eyebrow Dormers

Eyebrow Dormers

Eyebrow Dormers are the least expensive dormer option. Eyebrow dormers lack side walls and blend into the surrounding roof, and are relatively flat. These are more of an aesthetic choice or used to add more light to a room, not for additional space. 

Eyebrow dormers cost roughly between $100-$160 per square foot, or between $3,000 and $5,000. 

Cost Range: $3,000 to $5,000

Flat Roof Dormers

Flat Roof Dormers

Flat Roof Dormers are the most space efficient dormer option. Although flat roof dormers are not as aesthetically appealing as other styles, that roof dormers will provide you with more space for your money and also allows for larger windows. 

But one risk of going with this dormer style is the potential for leaks because the roof of this dormer is not sloped. Without a slope to the dormers roof, rainwater and melting snow are not able to slide off the roof and could cause leaking without using proper preventative material such as PVC.

Flat roof dormers, along with gabled roof dormers, and shed dormers are probably the most modern dormer roof designs used in home renovations today.

A flat roof dormer’s price does vary but the average price for is roughly between $80-$125, which ranges betwen $1700-$28,000. One of the more expensive options but the dormer style that gives you the most space in your home. 

Cost Range: $1,700 to $28,000

Shed Dormers

Shed Dormers

Shed Dormers are not added to homes as often as gabled dormers, but are more functional than a gabled dormer. Shed dormers can be added when wanting a flat roof dormer without risking the chance for leaks. Shed dormers are the same as flat roof dormers other than the fact they have sloped roofs, rather than flat. 

Shed dormers are the best option when adding a dormer for the additional space. Unlike a gabled dormer, shed dormers do not have a peaked roof but rather a flat roof with a slight pitch creating more squared off space. Shed dormers’ pitch are a major benefit because they are far less likely to leak. 

Shed dormers cost also range in price from around $6,000 for a 12 foot long dormer to about $12,000 for a 30 foot long dormer.

Cost Range: $6,000 to $12,000

Wall Roof Dormers

Wall Roof Dormers

Wall Roof Dormers is a type of flat roof dormer or shed dormer but makes a wall roof dormer different is that the wall of this dormer is an extension of the home’s exterior wall.

This type of dormer creates the most floor space because of how far the wall of the dormer extends to, making more square footage.

These dormers may cost a bit more in material costs but construction and roofing costs are lower because this style involves more siding.

Wall roof dormers range from $70-$120 per square foot, ranging between $25,000 and $40,000.

Cost Range: $25,000 to $40,000

Floating Dormers

Floating or “False” Dormers

Floating or “false” dormers (also called fake dormer), are used when a homeowner wants the external appearance of a dormer but does not need or want the additional space added inside the house.

Floating dormer roofs do not penetrate the roof, they are strictly for the cosmetic look of adding a dormer to your home.

Be advised, these floating dormers are strictly cosmetic, they do not offer any additional space, light, or ventilation to your home. 

So maybe you just like the aesthetic and look of a dormer style, there’s still a dormer roof for you! 

How much does a fake dormer cost?

Floating dormers cost the least to build because they are not actually cut through the roof. Floating dormers range from $4,000 to $5,500.

There are many dormer roof and window styles to choose from, it’s all about choosing the best dormer roof for your home!

Cost Range: $4,000 to $5,500

Do Dormer Roofs Need Gutters?

Many would not think of this small detail when working on such a big home improvement renovation..but it is an important detail.

The answer is depending on your dormer roof’s design, but many types of dormer styles do need gutters.

When adding eyebrow dormers to your home, gutters are not necessary.

Dormer roofs that are installed to extend living space, such as flat roof dormers, shed dormers, or wall roof dormers, gutters are necessary.

Gutters will prevent wear and tear on the roof below the dormer roof extension and also will prevent run off into the windows.

Again, a small detail but an important one when planning a dormer extension.

Do I Need a Permit to Add a Dormer to My Home?

Whenever doing a home renovation, you will often need permits to do so.

The easiest way to know which permits are needed is to contact your local building department and ask.

Whenever a renovation changes a home’s plumbing, electrical, or structural foundations, permits are required.

 Again, get your necessary permits here for your Long Island Dormer Home Renovation here: Permit Applications

Home owners can face serious fines if renovating their home without permits. In order to save yourself (and your wallet) the headache, make sure to get your home renovation permits!

But wait.. WE are licensed and insured in both Suffolk County and Hampton County and keep up-to-date with ALL building codes. Don’t hesitate to contact us with your type of property and your address so we can provide the best permit consultation for your dormer installation!

Mother-Daughter Extensions:

One very common use for flat roof dormers, shed dormers, and wall roof dormers are Mother-Daughter Extensions.

Mother-Daughter home renovations have become extremely popular in recent years.

There are two main reasons Long Island families are converting their home into a Mother-Daughter extensions.

The first being aging  parents who need assistance but also still need their own space. Mother-Daughter extensions bring peace of mind knowing they have their family and parents close but all still have their own space.

Another reason being older children coming home and needing their own space but not being financially stable enough to purchase their own home yet.

In today’s financial climate these extensions are becoming more popular for families with children out of college who need to move back home but also need their own space and privacy.  

On Long Island, family dormers and extensions are becoming the best financial decision for homeowners. 

Mother-Daughter dormer extensions can range between $40,000 to $90,000.

Don’t let that cost scare you!

Many homeowners that are adding Mother-Daughter dormer extensions can use this renovation to make a profit and bring up the home’s property value!

Homeowners can add a dormer to their home to convert their home into a Mother-Daughter renovation and can rent out one of the units. 

Mother-daughter home conversions allow families to live under the same roof, but have their own space. 

Don’t Forget to check your local permits!

Why Choose A Father of Four for Your Home Renovation?

LIMITED TIME OFFER: Save $1,997 with A Father of Four’s Dormer Discount
Teachers, Police, and Military Discount available! Take up to an extra 10% OFF your project.!

Adding a new dormer to your Long Island home is a great way to bring your home to the next level (get it?) not only your home’s functionality, but its aesthetic and property value as well.

With over 28 years of experience and real focus on customer satisfaction, you can rely on this Father of Four for the dormer roof installation on your Long Island home!


If you’re looking for the best dormers on Long Island, you are in the right place. We pride ourselves on being a construction company on Long Island that truly values our customers and their homes.

We provide professional home improvement services for families all across Long Island and will always treat you like family!