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Adding onto existing basement


How to plan a basement extension – what permits do I need and how do I design my basement? |

(Image credit: Abramson Architects/Jim Bartsch)

If you’ve outgrown your living space, knowing how to plan a basement extension can be a fantastic way to make the most of the home you already have. Not only can this type of project add space and value to your house, but it has the potential to transform how you use it, too. 

Whether you’re finishing an existing space or excavating to create a new basement, it’s a big job. There’s a lot to consider, from finding an architect who shares your vision for the space, to more technical aspects such as ensuring the basement is watertight and well-ventilated. 

Obtaining the right set of permits to ensure the work is legal is another important step. Here, we outline the essentials facts you need to make your basement ideas a reality.

This sunny basement in Boston was designed by Beige & Bleu to provide a zone for the teenage girls who live here. The space already had windows, so it made good sense to finish it off and extend the house’s living space into the lower level. Wood-effect vinyl was chosen for the floors.

(Image credit: Beige and Bleu/Tamara Flanagan)

How to plan a basement extension?

Planning a basement project is very similar to any other home renovation project. Before approaching any designers or builders about your project, get clear on what you want to get out of the build. 

I would think about function,' says Liz Caan, founder and principal at Liz Caan & Co . 'What activities need to happen down there? Will you truly use these areas for those functions?'

The basement conversion costs and complexity of your project will depend largely on whether you have an existing space that can be converted/renovated into a habitable zone, or if you need to carry out excavations to make your goals feasible. 

The practicalities and challenges of building below grade are different to those you’ll face when constructing an extension at grade level, so you’ll need to bring in the right professionals to ensure your project is a success – and to make the most of your basement.  

'Due to the nature of the basement being below grade, there’s different challenges that need to be met,' says Christopher Tucker, principal/owner at MODE4 Architecture , a design practice based in Alexandria, Virginia. 

'Namely, designing to allow for natural daylight and emergency egress. Additional hurdles might include low ceiling height, location of mechanical and utility equipment, electrical panels, sump pumps and crocks, and structural columns.'

Added to that is your wishlist: do you want to include just basement bedroom ideas and basement bathroom ideas – or will basement kitchen ideas form part of your planning, too?

Portland-based Polymath Studio worked with Hammer & Hand on this basement remodel. The project transformed a dark, unfinished basement into a bright living area and playroom. One of the key design features is the barn door with an inlaid chalkboard, which can be drawn across to hide the kitchenette or the bookcase.

(Image credit: Polymath Studio/Jeff Amram Photography)

How do I find an architect? 

Tigg + Coll Architects revolutionized this rundown London home by carrying out a complete renovation, which included the addition of a new basement. The addition of a front light well ensures the space is flooded with natural light.

(Image credit: Tigg Coll Architects/Andy Matthews)

Once you’ve created your wish list for the basement extension, tracking down a professional designer to take the scheme forward is the next step. 

As well as having the skills to draw up plans and put together a layout for the space, an architect will be able to suggest innovative ways to maximize the area. They may also come up with design ideas that you never would have considered. 

'An experienced architect will also understand both the technical and the experiential elements – natural light, fresh air, spatial configuration, etc - challenges inherent in finishing a basement,' says Sean Barnett, owner and principal architect at Polymath Studio Architecture .  

'The technical elements include waterproofing, code requirements and egress for vertical clearances, while the experiential would cover natural light, fresh air, spatial configuration, etc. At a minimum, the space will need to be insulated and an appropriate means of accessing the space and exiting will need to be provided.'

When it comes to deciding on the layout and aesthetics, an architect’s insight is invaluable. The right professional will be able to tease out your initial ideas to create a basement that oozes wow factor. 

They can provide advice on fixtures and finishes, as well as taking a dynamic approach the plans if any unexpected hiccups occur during the build. Working with an architect has the potential to take some of the stress out of the process, too, as they’ll be able to assist with the project management. 

Your chosen professional should maintain good working relationships with all your contractors and will have a strong grip on the timeline for the project, looking after what needs to happen and when. 

Remember, it’s important to discuss exactly what duties you expect your architect to perform at the start of the project so it can be built into the contract.  

Word of mouth is the most common way to track down a good architect, so be sure to discuss your upcoming project with friends and family to see if they have any leads on a good designer. 

There are plenty of online resources, too, including resource tools at your local chapter of the American Institute of Architects .

What about the rest of my project team?

Architecture firm Touloukian Touloukian gave this mid-century colonial house in Massachusetts a new lease of life. A board-formed concrete structure was extended to the rear of the home, substantially increasing the size of the lower level. 

(Image credit: Touloukian Touloukian/Anton Grassl)

Once you have a skilled architect on board, he or she might be able to recommend a contractor for the building work. 

It’s also worth talking to friends, family and colleagues to see if they have any recommendations for firms with experience of building or renovating basements. 

When you’re sourcing quotes, ask to see examples of builders’ previous work and talk to past clients. You’re investing a lot of money in your project – taking time at the start doing to track down the right team of people will pay dividends later. 

An interior designer will be another useful addition to your project team. Get online  to find ideas and inspiration – any designer worth his or her salt will be able to translate these sparks of inspiration into a detailed strategy for finishing the space. 

Hiring a professional who has experience working on basement projects could also help you avoid costly mistakes later in the project. Plus, they’ll know where to go for resources and products, which will save you a lot of time spent researching brands, prices and product solutions. 

If you’re keen to get involved in sourcing materials yourself, architectural salvage centers and antiques stores can be a fantastic resource, in addition to home improvement stores.

How much will a basement extension cost?

Designed by Abramson Architects , this basement living area benefits from plenty of natural light thanks to the addition of several light wells. The lightwell pictured here features a set of steps that lead up to grade level. The basement also features a separate entrance so people can come and go without disturbing the rest of the household. 

(Image credit: Abramson Architects/Jim Bartsch)

Basement conversion costs are determined by a host of factors, from the condition of the existing structure to the level of finish you want to incorporate. 

As a general rule of thumb, smaller projects are likely to cost within the region of $55,000 to $75,000. Middle of the road projects sit around the $85,000 to $100,000 mark, while larger builds could cost $200,000 and above.

The condition and age of the existing property plays an important role in determining project cost. 

'For example, if the existing basement has a history of taking in water, a new sump crock in the sump pump will be required,' says Christopher. 'Some of our basement projects require underpinning of the existing basement walls to achieve a taller ceiling height, too. ' 

Once work begins, your builder may also uncover structural defects that need to be remedied for progress to project. Always incorporate a contingency of 5% to 10% to cover these eventualities.

The overall outlay will also depend on what features you want to include in the lower level. For example, specialist zones such as gyms, wine storage areas and movie theatres will all drive up costs because of the cost of equipment. That’s why it’s important to be realistic with your budget from the start and bring your architect into the picture so they can help you manage cashflow. 

It’s also their job to lay out clear parameters from the start of what can – and can’t – be achieved financially. Remember, as well as accounting for the build and materials in your budget, you’ll need to allocate funds to consultancy fees and permits, too.

Do I need a permit to build a basement extension?

This lower ground floor kitchen was designed by Mulroy Architects in London. The original internal brick wall was retained to create a feature. An acoustic timber baffled ceiling was incorporated to form a more textured counterpart to the smooth surfaces throughout the rest of the space.

(Image credit: Mulroy Architects/Will Pryce)

Since the work isn’t visible from the street, excavating, remodeling or finishing a basement is sometimes a job people will try and get away with without having the necessary permits in place. However, this can be a costly mistake. 

If your local building department gets wind of the fact that you’re building without permission, they’re within their rights to ask you to take everything down and start again from scratch. 

Plus, if you ever come to sell the house in the future, it’s important to have the necessary paperwork in place – a realtor will want to see the building permit for the remodeled area of the house. If you can’t produce one, the property could lose value.

'A typical building permit is required if electrical, mechanical and plumbing are involved, but this can be different from one jurisdiction to another,' says Christopher from MODE4 Architecture. 'Always check local building code and permitting requirements.'

All the alterations you make to the house must be up to the standards laid out by the local building code, too. These stipulations vary, but generally the ceiling height in a finished basement must be at least 7 ft. Some lower obstructions are permitted, such as structural beams that can’t be relocated. 

You can pave the way for a smooth process by reaching out to your local inspector early on in the project – they are more likely to be sympathetic to your goals when consulted early on in the build.  

You’ll also need to meet the requirements for doors and windows as a means of emergency escape, as well as staircases.

As part of the gut renovation of this home, the unfinished basement was transformed via the addition of a playroom and large workout room. Liz Caan masterminded the interior design, including fun flourishes such as the ceiling-hung chairs.

(Image credit: Liz Caan/Eric Roth Photography)

Can I frame my basement without a permit?

Designed by architecture firm Touloukian Touloukian the existing grade change from the front to the back of the house allowed for an indoor/outdoor transition to the new basement via timber frame glazed sliders.

(Image credit: Touloukian Touloukian/Anton Grassl)

Putting up drywall framing is a swift way to transform an unused space into a functional living area. If you’re a competent DIYer, this may well be a job you can tackle yourself – but that doesn’t mean you should skip getting a permit! 

Problems can arise further down the line if you tackle renovation work without obtaining the necessary permissions first. Even though you’re not a professional contractor, the same filing and permitting requirements apply. 

Every county has its own set of zoning and development rules, so check with your local Building Department regarding what is required. 

The price of the permit depends on the county development laws and the size of the project. For a smaller scheme, the permit could cost as little as $100. 

If your project adheres to code, you’ll be able to complete it without any trouble, and you’ll save yourself from any potential legal complications further down the line.  

Sarah is a freelance journalist and editor. Previously executive editor of Ideal Home, she’s specialized in interiors, property and gardens for over 20 years, and covers interior design, house design, gardens, and cleaning and organizing a home for H&G. She’s written for websites, including Houzz, Channel 4’s flagship website, 4Homes, and Future’s T3; national newspapers, including The Guardian; and magazines including Future’s Country Homes & Interiors, Homebuilding & Renovating, Period Living, and Style at Home, as well as House Beautiful, Good Homes, Grand Designs, Homes & Antiques, LandLove and The English Home among others. It’s no big surprise that she likes to put what she writes about into practice, and is a serial house renovator. 

Can You Add Onto An Existing Basement? – Basementing.com

Lately, home offices, home schools, and home businesses are the new trend; you might need a more permanent place other than the kitchen table or your bed. Any unsalvaged living space such as a basement could be used as a class or office. The question that may arise at this point is: if the basement isn't big enough, can you add to it? We asked experts, and they gave us conclusive answers.

Yes, you can add onto a preexisting basement. Technology and know-how make it possible to add much-needed square footage to a basement already in place. Before you start enlarging your basement, you must consider the following aspects.

Even though this isn't a project, you can have input by understanding what it will entail. After considering these factors thoroughly, call in the professionals to turn your dungeon into a spacious sanctuary. Continue browsing as we dissect each aspect of adding onto an existing basement.

What To Consider When Adding Basement Space

Basements are sometimes not utilized to their full potential due to them being too small. Professionals can rectify the problem by enlarging the basement.

There are some vital factors you must consider before embarking on such a project. Once you have taken all of these into consideration, you'll then know whether or not to add to your existing basement.

Type Of House

Your home might have a basement, but the size isn't satisfactory. Adding more space will solve this problem. The type of house you have will determine if this will be possible.

A newer home will be the best candidate for any enlargements because there's a lot of extensive excavation involved. Foundations of newer homes are more stable than older homes. Hire professionals to access the condition of your home especially the foundation, basement walls, and plumbing.

Soil

A completed house has its configurations according to its initial planning. When you want to add some square meters to the basement, you'll have to do some digging.

Different soils behave differently when any structure is erected on them due to their different properties. Land surveyors can assist a homeowner to understand what to expect in terms of shift, expansion, and water retention of the soil in the vicinity.

Climate

When making any alterations in your home, ensure that you think about the season and the climate. If your home is located in a warm climate, don't start any basement expansion in the rainy season. Homeowners in colder climates should start any work on their basements in the cold months.

The basement walls don't need to be subject to extreme weather in an uncompleted state. They are part of the house foundation, and any cracks will damage the house as a whole.

The cost of the operation might hike due to cracked walls, burst pipes, or necessary additional insulation.

Local Building & Construction Codes

Homeowners must be aware of the fact local building construction codes differ depending on the state. The codes regulate the height of the ceiling, sizes of doors or windows, and emergency exits. As a homeowner, don't skip this stage under any circumstances.

You could check with the local building authorities to know what you can and can't do in your home. To avoid penalties, seek the help of a professional company.

Estimated Cost

Just like in any home upgrade, you should be aware of approximately how much you'll have to spend to get your desired basement. The cost will consist of; permits, land excavation, materials, equipment, installations, insulation, finishing, and professional labor fees.

Before hiring any professionals, get several quotations but don't skim on the quality of work or materials. This way, you'll be sure of getting guaranteed quality results.

How To Build A Room In A Finished Basement

Adding a room to a completed basement is an easy task for any capable construction professional. Remodeling a house makes it feel more like a home to a homeowner.

Building a room in your finished basement might or might not be complex. You won't get any additional living space but it can improve the functionality of the area. Ensure that you check out the building codes about the type of room you want to build.

Before any construction, you should hire a professional to draft architectural plans, have a proper basement layout, and identify the load-bearing walls and support system.

What to do when building a room in your basement:

  1. Draw a plan: Have a carefully laid out plan of the room you want to be added.
  2. Frame the walls: Locate the joists in the basement ceiling where the walls will be fixed. The wall frame must have a top plate, a bottom plate, and studs. Include allowances for doors in the wall frames.
  3. Wiring: Ensure that you wire the room accordingly. Drill holes where necessary.
  4. Plumbing: Add any needed ducts and pipes to the new room.
  5. Install and paint the walls: Once the wiring has been completed, erect the walls, smoothen them out, and paint.
  6. Flooring: Lastly, lay the desired flooring after completing the walls.

Below, find a helpful tutorial on framing walls to add a room to a basement:

How Much Does It Cost To Add On To A Basement?

The cost of adding on to a basement ranges from $20,000 to $150,000. The cost will vary according to the size of the addition and prices of material and labor in different states.

Most professionals charge at least $100 of the work done per square foot. A lot of work goes into adding on to a basement. The fee includes:

How Can I Make My Basement Safe To Live?

To make your basement safe to live in, you must adhere to any regional rules and regulations. Building and construction codes stipulate that any living space must have the following:

  1. Basements must have doors and egress windows which also serve as emergency exits.
  2. Ensure that your basement has all these exits easily accessible in case of emergencies.
  3. Insulate the basement properly to avoid heat loss.
  4. Additional measures such as fire sprinklers, fire extinguishers, and alarm systems are must-haves for residential properties.
  5. Check for any pests and fumigate if necessary.
  6. Use dehumidifiers to reduce moisture and mold.

When these measures are in place, you can feel safe and secure in your basement.

Is There Such Thing As A 2 Story Basement?

Yes, there is. Generally speaking, a basement will be considered a story that is below ground level.

The term story basement is commonly used in commercial buildings such as banks, offices, or underground car parks that have two grand planes. One grand plane might be below ground level whilst the other is above ground level. The height in between the floor should be not less than six feet.

In residential buildings, the basement is sometimes used as a living quarter. It is simply identified as a unit because the residents are non-transient.

Summary

Any additional living area is always welcome. To achieve this, you'll need the help of professional builders and contractors. Adding on to your to an existing basement might be costly as it is almost like new construction.

As a homeowner, you must realize that embarking on such a project might be time-consuming and expensive. Ensure that you have all the estimated costs and quotations from several accredited professionals.

To make your basement safe to live in, adhere to any local building codes. Decorate and create an ambiance to go with the function of your basement area.

Here are posts to give ideas on how to make your basement more hospitable and habitable:

How To Bug Bomb A Basement

Can You Epoxy A Basement Floor?

How to attach a basement to a building so as not to disturb the existing foundation?

Greetings, my Readers and Viewers of the construction Blog “Way Home”!

Today will be looking at a topic that is a bit in tune with one of the recent webinars. Namely, “Is it possible to strengthen the existing strip foundation by increasing the width?” I then talked about the basic principles of technology and that there are no problems with this. Today's topic is very close in spirit. In fact, the solutions that I talked about in the topic about the strip foundation, they are also applicable to this issue. nine0003

Full question: Andrei Dovgan/ How to attach a basement (an extension with a basement) to a building without a basement so as not to disturb the existing foundation, is it possible to build a basement inside an existing building? Basic principles, technological sequence, nodes.

Those who think that this is reconstruction technology, I want to disappoint you a little. I immediately remember one object that we did many years ago. Contact with the client was not lost, so I know that the house continues to stand safely. nine0003

This was new construction. But due to the fact that there was an old house on the site where they wanted to build a garage, they were going to build it after the construction of a new house. We did everything as I described in the video. Issues were made for the foundation, everything is as it should be. The only thing left to do was build a garage. But the client waited out the winter, and then, after thinking, he decided to make a basement under the garage.

Can you imagine? On the left is a house, already finished, lined. You bear a full guarantee for its safety. It is without a basement, on an ordinary strip foundation, and here the client wants to attach a garage close to the house with a basement! How we did it, I'll just tell you 🙂

1:32 Photo examples
10:00 How does it work?
12:50 Planning decision
15:00 Building plot and foundation
17:33 Foundation type
18:00 Basement inside the house
19:20 Why is it better not to build a basement inside the house?
20:15 How it works
21:15 Lowering the structure into the pit
25:15 Knots

User questions

26:10 How do you feel about plastic caisson basements? Do I need to take into account something when deepening them? nine0015 28:41 I don't understand how you can make a basement under the house, because it will not be possible to waterproof the foundation walls from the outside. And it will not work to connect the horizontal waterproofing of the basement floor with the vertical one.
31:22 In addition to building an extension with a foundation deeper than
the existing building, there is a need to overlay the existing house with one row of bricks. Is it possible in this case to make a complete one with an extension of the foundation
32:36 How then to properly organize the floor under this gear structure? nine0015 34:39 Question for the first example. Is it possible to replace the consoles with a shallow tape if the house is on a tape of full penetration?
35:40 Did I understand correctly that any foundation that is smaller than the foundation of a house can be safely made back to back?
36:05 Should the hard foundation of the house be tied to the new addition?
36:36 You drew a diagram of the internal waterproofing, but it's not dangerous, because the foundation will always be damp?

Best regards, Alexander Terekhov

Creation of an extension with a basement to apartment

Unlike your own house, it is difficult to enlarge a separate apartment. One of the possible options is construction of extensions . This method is applicable for the first floor, but is sometimes used by those living on the second. The main focus is often on expanding living space, but sometimes property owners create outbuildings for household purposes, placing cellars or basements for food storage and conservation under them.

The cost of an extension to a house cannot be compared with the replacement of an apartment with a large one, so in our cities you can increasingly see such additions to multi-storey buildings. Prior to construction, you need to obtain permission, and then select the appropriate materials. There are various options for doing what you want to do. nine0003

Much depends on the configuration and location of the apartment. The structure can be done along the wall or done under a window or balcony. In addition to the rectangular shape, L-shaped extensions can be seen near the houses. This is the prerogative of residents of corner apartments.

Before contacting the permitting authorities, you need to get information about laying communications to the house, because during the construction of a basement or cellar, they can be accidentally damaged.

The first step is to talk to the management of the ZhEK and local authorities in order to obtain the necessary permits. The presence of official documents will prevent disputes during the construction of the facility and in subsequent operation. Unauthorized construction will result in a fine and the demolition of illegal structures. nine0003

Preparing the foundation for construction

To choose a suitable foundation, you should first understand the type of soil and determine the area of ​​​​the future extension. The option chosen should also take into account the prospect of digging a pit and the need for a cellar or basement. Among the existing types of foundations, columnar and strip foundations are most suitable.
For long-term reliable operation of the building, when choosing a tape type of foundation, it should be laid below the freezing line of the soil. This will protect the extension from significant shrinkage and cracking. Otherwise, you will have to completely redo the design or refuse to operate. nine0003

If the cellar is not needed, the building area is small and the soil is good, then you can get by with the use of a columnar foundation. In all other situations, this option will be the worst possible. The tape base is a more versatile and convenient solution in most cases.

Various building materials can be used to create an extension. Among the familiar and popular, it is worth noting brick, foam blocks, cinder blocks, aerated concrete blocks and some other types. All of them are suitable for construction, so the choice is made by the owner of the apartment based on availability, availability of funds and desire. nine0003

Prefabricated reinforced concrete slabs or self-cast screed are used as a rough foundation for the floor. The process of its creation is not difficult. For her, you need to buy cement, sand, build a formwork. If the owner decides to use a ready-made slab, then difficulties may arise when arranging the entrance to the basement. You will have to cut a suitable hole in it with the help of tools. Do not forget about the fittings located inside. It is much easier to use a screed when creating a cellar. During pouring, you can immediately create a suitable entrance. nine0003

Preparatory work

It is better to postpone all stages of construction for the summer period. At this time, groundwater is at its lowest level and the soil is dry. Before digging a pit, marking is carried out on the surface. Before construction, they must consult with the craftsmen regarding materials and construction, a draft project of the future extension is being created.

Once the planning phase is complete, site clearing and earthworks begin. According to the existing marks, a hole of the required depth is torn off, taking into account the height of the future basement and the thickness of the ceiling. In addition, a small margin is needed for adding a sand cushion and the height of the foundation. nine0003

In order for the future shrinkage of the extension to take place without noticeable damage to the structure, a place is first left for the expansion joint. Its thickness lies within 3-4 cm. In the future, after the construction of the extension, it will be covered with facing material and will not be visible from the outside.

If the entrance to the extension will take place in the window area, then you will have to make changes to the load-bearing wall and create a hole that is suitable in size. Usually the existing width is left, the height is planned flush with the top of the window, and the masonry under it is knocked out. nine0003

Creation of the foundation

If the foundation pit is excavated, then a layer of sand is placed on the bottom, which is moistened and compacted. The final height of the layer should be 0.15-0.2 m. If the weight of the building is large, then it is better to pour up to 0.3 m from a mixture of sand and gravel. After each filling, tamping occurs. The future design will be more stable and reliable.

A good strong base needs reinforcement, so a grid of metal bars is created on the sand cushion. Individual elements are twisted with pieces of steel wire. After the reinforcement is created, the foundation is poured with a cement-sand mortar. Subsequent construction is carried out only after the final hardening of concrete. Haste with the construction of the object is fraught with future cracks.

After the base has hardened, waterproofing of the future basement floor must be carried out. This will save the room from excessive moisture and related troubles: flooding, the appearance of fungus and mold. Roofing material or bituminous mastic is usually used as insulating materials.

Basic work

The walls are erected in the usual way. Standard laying of blocks or bricks, for example, occurs on cement mortar, each row overlaps the previous one. The evenness of the masonry and the correctness of the geometry of the entire extension are periodically checked. To increase the service life, modern plasticizer additives can be added to the cement slurry. They will help in creating a monolithic structure.

A ready-made concrete slab is often used as a roof, with the obligatory implementation of a set of measures for waterproofing against precipitation. To prevent moisture from accumulating on the roof during rain, you can make it with a slope. In this case, sheet roofing material is used. In addition to the usual slate, there are a number of more interesting and technologically advanced materials such as metal tiles. For its laying, a frame is created from wooden bars with a crate. nine0003

Once the roof is finished, the interior work can begin. Depending on the scope of the resulting additional area, various materials can be used. If the premises will be used as residential, then it is additionally insulated and electrified. In some cases, even heating is carried out. Do not forget about the window or even several. Without them, being in the room will not be comfortable.

Is a basement always allowed? nine0067

It is often for the sake of it that apartment owners start such construction. It will become a reliable room for storing conservation and other products. No need to go every time for a kilogram of potatoes or a jar of compote to the garage, or go to the country.

To create a dry basement, you must carefully follow the recommendations for waterproofing, otherwise it will become unsuitable for its purpose.

You have to give up your own basement in areas where the groundwater level is too high. In such cases, the cost of moisture protection will make the project too costly and unattractive for the apartment owner.

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