When building or buying a house, a deciding factor may be a crawl space vs basement. To some, it may not matter, while others view it as a deal-breaker. So, what’s the difference?
The main differences between a crawl space and a basement are ceiling to floor clearance, floor, windows, and access. Crawl spaces typically have clearances less than 48” and a basement is 8’ to 10’. Basements commonly have a level concrete floor and windows, while crawl spaces may be unlevel dirt, gravel, stone, or concrete floors, and seldom have windows. Basements also have access from within the structure, and crawl spaces often don’t.
In this guide, we’ll explain what a crawl space and basement are, and look at their similarities and differences. We’ll identify the pros and cons of both spaces, discuss crawl space vs slab, compare a cellar to both, look at converting a crawl space into a basement, and if you can have a half basement-half crawl space. Our goal is to provide you with the information to make an informed decision as to which is best for your needs.
What Is a Crawl Space?
A crawl space is the shallow unoccupied open area underneath the first floor of a house. It raises the structure above ground level, and may be excavated or simply the hollow space between the sloped ground and the level floor joists.
The joists often rest on beams supported by piers or posts on pads or footings. The ground to joist clearance ranges from zero to 48”, which means you crawl instead of walking upright. About 15% of new home construction in the U.S. has crawl spaces.
Crawl spaces can be open or enclosed with a frame, block, or concrete perimeter wall or foundation, and require venting to prevent moisture and ground gas build-up. Access to the space is usually from the exterior of the structure, and there are seldom windows to shed light, although screen vents will provide some lighting. The space may be insulated but is usually unfinished. Open crawl spaces have few, if any, enclosing walls and thus aren’t insulated.
Not all crawl spaces are created equal, some are dry year-round, wired with lighting and outlets, and rodent and mold free, others aren’t. The space provides access to HVAC, electrical, and plumbing, and some storage space for whatever fits. Plus, the space allows air to circulate under the structure, removing moisture and gasses, and helping to prevent molds and mildew.
What Is a Basement?
A basement or basement foundation is an architectural component of a structure upon which a building with one or more levels sits. The modern basement with potential for living space dates back to the 1950s, prior to that, they were commonly cold storage cellars often containing a cistern and having few or no windows and an unfinished floor.
Today, it typically has a level concrete floor, windows that offer light and egress, and is accessible from inside. The floor-to-ceiling clearance is commonly between 8 and 10-feet but may be as low as 7-feet in older homes. Most basements are dug so the footings are below frost level, so are usually 4 to 5-feet below the ground level. About 31% of new homes in the U.S. have basements.
The basement is the excavated area located within the foundation walls. The walls may be concrete, block, stone, framed, or a combination of two or more of these materials. Depending on the topography, basement walls may be fully or partially underground. They may be walk-out or require window wells to ensure lighting and points of egress, especially if the space is used for living or sleeping purposes.
Basements provide access to electrical, plumbing, and HVAC, the potential for extra living or recreational space, and space for storage. The clearance in basements is such that most people can comfortably stand upright too. Basements are commonly included within the heating and cooling functions of a structure, so moisture, gasses, molds, and mildew are kept under control.
Crawl Space vs Basement: Key Points?
A basement and crawl space are not the same things, even though they both are found under the main floor living area. They both may often be damp, full of spiders, and even scary, but one you may stand upright in, and the other is safer to crawl in.
What Is the Difference Between Crawl Space and Basement?
Crawl spaces and basements have some similarities but they are not the same. While they both are located under a structure and provide access to plumbing, electrical, and HVAC systems, their differences are significant.
The clearance is the distance between the floor surface and the undersides of the floor joists of the floor above. Most modern basements have a clearance between 8 and 10-feet. Older basements may be as low as 7-feet. For most crawl spaces, the clearance ranges from 48” down to zero, with the average being 18” to 36”.
When looking at the space under home, only a basement offers the potential for livability. With clearances of 7 to 10-feet and a level concrete floor, the space can be insulated, heated, cooled, and dampness can be controlled or eliminated. Most basements have windows, and the foundation walls can be cut to enlarge the windows to meet egress requirements. Additionally, basements are usually accessible from within the structure.
The clearance of a crawlspace doesn’t lend itself to comfort. The floor is often uneven or sloped, exposed dirt, gravel, stone, sand, or possibly concrete, and may be seasonally or continuously damp. The space may or may not be enclosed, and if it is there are seldom any windows. Some crawl spaces aren’t heated, cooled, or even ventilated, and may be home to rodents and other critters. Plus, access to most crawl spaces is from the exterior of the structure, not the inside.
Construction costs, materials, and location determine the structural costs. Basement foundations typically use more materials, equipment, labor, and time to excavate, form, pour or place. The cost of a basement can range from $25 to $90 a square foot or more depending on all factors. Basement walls are commonly twice or more as high as crawl space walls, so more expensive.
The cost of a crawl space or basement often depends on the structure’s size, ground topography, soil composition, and local codes. The crawl space is created when the level floor deck is constructed. A post and beam system or footing and foundation walls are used to support and level the main floor deck. The amount of work and materials that go into the support system determines the cost. The cost can range from next to nothing in some cases to between $7 and $10 a square foot.
Excavating for footings, pouring them, and then forming and pouring perimeter concrete or laying concrete block foundation walls is usually more expensive than piers or pads and posts. I’ve seen crawl spaces on sloped ground with cedar posts and others with dry stone piers sourced on-site carrying beams upon which sat one, two, and even three-story homes, so aside from labor, the cost was negligible.
To keep insects and rodents out, and make the space dry year-round, warm in winter, and cool in summer, means encapsulating it. The cost of such an exercise can easily exceed $15,000 depending on area, issues, and location. Basements are commonly easier and cheaper to encapsulate than crawl spaces too.
Moisture issues often depend on location and local climate. Building on wetland versus high well-drained ground is a case in point. Plus, humidity and evaporation can lead to moisture issues such as mold, mildew, and rot. Most crawl spaces are affected by seasonal moisture and humidity, especially if enclosed. However, as long as they are properly vented, the moisture doesn’t cause too many problems.
Basements are enclosed structures within semi-permeable concrete or block foundation walls. Seasonal moisture can seep in, and summer humidity can build up unless the space is properly conditioned and vented. To prevent molds, mildew, and rot, it is important to seal the foundation walls, dehumidify the space, install a sump pump, and heat-cool the space as required, otherwise, there will be health and structural issues.
Perimeter basements walls are typically made of concrete or concrete blocks, making them stronger and more durable than most crawl space perimeter walls. Basements are also partially to almost fully underground and so offer greater stability and protection from storms and earthquakes, while crawl spaces are usually elevated above the ground and may or may not be open to the elements.
Basements tend to be more visible, so if there are moisture or other issues, they are addressed sooner. Crawl spaces are checked less often or until there is a problem, which may make for more health issues and costlier repairs. Additionally, basements are easier to encapsulate and condition for moisture and temperature, which means fewer issues with rodents nesting or eating wires and pipes and the associated health and safety concerns.
Crawl spaces and basements can account for up to 30% of the heat or cooling loss from a building. Insulating the joist cavities of the floor above an open crawl space and including moisture and rodent barriers will improve the energy efficiency, The same can be done with an enclosed crawl space, or the walls can be treated as a short basement and insulation and vapor barrier installed.
Improving the energy efficiency of a basement is a common practice. Strapping or framing the inside of the perimeter foundation walls, insulating between the studs, and applying a vapor barrier are all fairly easy since you can stand up to do so.
Alternatively, the floor joists that form the basement ceiling can be insulated like a crawl space. However, it is usually less expensive to insulate walls as the stud framework is 2” to 6” deep versus the joists which are 6” to 12” deep or more.
The ground or pad should also have a moisture vapor retarding liner to keep ground released contaminants out. It is also important to insulate any exposed plumbing pipes and heating ducts, and seal openings through the barrier. Additionally, never vent the clothes dryer into the basement or crawl space.
Most basements that are properly sealed, whether insulated or not, will experience spiders, millipedes, the possible cricket, and even, occasionally, mice. Enclosed crawl spaces with perimeter walls built with a below-ground footing or beam will commonly experience the same sorts of pests. However, open crawl spaces and those with perimeter walls that just sit on the ground can have mice, spiders, and other creepy-crawly insects, snakes, skunks, chipmunks, and raccoons. Open crawl spaces can also house foxes, bears, porcupines, groundhogs, and other uninvited occupants.
Radon, a radioactive gas produced naturally as radioactive metals break down in soils, rocks, and even groundwater, can seep into buildings through cracks, gaps, and unsealed ground. It is odorless, tasteless, and invisible, and can lead to lung cancer. It is second only to cigarettes as a cause of lung cancer. A simple radon test kit or hiring a radon inspector will identify if there are any radon gas concerns.
Radon mitigation begins with a plan to seal entry points into the home where gas can enter. Sealing cracks and gaps in the perimeter basement or crawl space walls and floor, including plumbing, HVAC, electrical openings, sump pump openings, and around support posts decreases gas entry points. There are even special traps for floor drains that help too.
Covering crawl space floors with 10 to 20 mil or thicker poly membrane is a step in the right direction. All seams should overlap by 12 or more inches and should be caulked and taped. The poly should go up the perimeter walls 12” to 24” or more and seal around posts and pipes through the floor membrane.
A continuously running power vent fan will help expel gas buildup from inside the crawl space or basement, coupling it with one that brings in fresh air will help reduce negative air pressure that can draw up gasses into the house enclosure. Alternatively, use a heat recovery ventilator (HVR) system.
Concrete basement perimeter walls and floor slabs are permeable to moisture and gasses and require a moisture-vapor barrier to mitigate most concerns regarding radon gas. Sealing all cracks and gaps in the concrete, including where pipes, posts, and other things go through will help mitigate radon concerns. Adding a passive slab ventilation system to allow gasses trapped under the slab to escape outside the house structure is helpful too. An HVR is another way to mitigate radon gas in basements.
Most buyers are looking at location, size, floor plan, curb appeal, and price when looking at a home, and some look at adaptability too. The resale value of a home is affected by its age, the lifespan of existing roofing, windows, doors, and appliances, plus the electrical, plumbing, and HVAC systems. Foundation damage can also affect the resale of a house. Some buyers prefer crawl spaces to basements too, which can also affect the value.
When looking at foundations, the type can also affect adaptability. A basement can be finished and adapted into living, sleeping, and recreational spaces, or into income-producing rentals. However, a crawlspace can also be turned into a basement simply by lifting and-or moving the structure to excavate and build a basement.
An open or enclosed crawl space raises the structure above ground level – which some buyers like – protects from run-off and, in some locations, termites. It provides access to electrical, plumbing, and HVAC systems, and also limited storage space – which some also prefer – and usually doesn’t affect resale value.
A basement provides the same access to utilities but has more storage space unless it has already been fully or partially finished – which can affect price, adaptability, taxes, and resale value. Repairing or fixing a structural support post is typically cheaper and easier than dealing with a broken or crumbling basement wall too.
The lay of the land and the amount of rain or seasonal flooding an area may experience often affect design decisions such as a basement or crawl space. Budget and the need for storage space, or the potential for extra living space or income are other considerations. Plus, the prospect of termites, accessibility, and local ordinances also affect whether to build a basement or crawlspace.
Crawl spaces are common on sloped ground, low-lying areas susceptible to flooding, or wetlands. A crawl space raises a building above the ground and forms a level building platform for the structure. Thus, making it best for areas experiencing high levels of moisture, run-off, and flooding. If properly vented or open, dampness is less likely to result in mold, mildew, and rot. Additionally, the raised structure is less prone to termites and other wood-boring insects.
A basement provides a more solid and durable base for areas prone to earthquakes, high winds, and freezing temperatures. However, they are also used in similar locations to crawl spaces too, but often require sump pumps to remove the threat of interior flooding.
Basements typically sit 4’ or deeper into the ground, placing them below frost levels. This helps to keep the adjacent ground from freezing, mitigating frost heaving and foundation damage. They also provide extra living areas that can greatly increase the structure’s value.
Advantages and Disadvantages of Crawl Space
A crawlspace may be a personal design choice or one that comes with the house you choose. They are more common in some areas than others, and makeup about 15% of new homes in the U.S. Regardless of the reason, here are some advantages and disadvantages to a crawl space. It is important to note, though, that many of the disadvantages can be mitigated with some effort.
- Provides access to plumbing, electrical, and HVAC.
- A potential location for the furnace, freeing up prime interior space.
- Accessible from outside so repair personnel don’t need access into the home to affect some repairs.
- Smaller space under the living area, so less expensive to build, heat, or cool.
- May offer some additional storage space.
- Raises home above damp or seasonally flooded ground.
- Offers protection from termites and other pests.
- Flexibility for some soil conditions or where hydrostatic pressure is a concern for concrete.
- Ideal for unlevel or sloped ground to provide a level building platform.
- Much less expensive to build and finish than a basement.
- Potential for dampness leading to mold and mildew growth.
- Air quality permeates into the home and can cause health issues.
- Open or closed could become home to unwanted ‘guests’.
- It’s a space where you have to crawl or slither over sand, gravel, dirt, rock, or maybe concrete to access anything.
- Can affect energy efficiency depending on location.
Pros and Cons of a Basement
Basements as we know them have been around since the 1950s. They commonly have larger windows, clearances of 8 to 10-feet, and a level concrete floor offering the potential to increase and improve living space. About 31% of new homes in the U.S. have basements. Here are some pros and cons to consider when choosing a home with a basement.
- Increases the square footage and potential living space of a home.
- Greater storage area.
- Utilizes the land and space better.
- Naturally cooler in the hot summer.
- It’s a multipurpose space.
- Potential for income-generating living space.
- Offers easy access to HVAC, plumbing, and electrical systems.
- More durable and stable foundation for windy or earthquake-prone areas.
- Accessible from the interior of the home.
- Fully or partially below ground, so potential for an emergency shelter.
- Works on a variety of landscapes, including sloped ground for a walkout basement.
- A finished basement or additional living space improves resale value.
- Larger, deeper, and more expensive to build.
- Expensive to finish and climate control.
- Moisture and dampness concerns.
- Below ground level so greater potential for flooding.
- Natural lighting may be an issue.
- An echo chamber.
Crawl Space vs Slab
Crawl spaces may be used on uneven ground or in damp or seasonally flooded areas. The space is the empty area between the ground and underside of the first floor and is the result of leveling with posts or walls to form a level building platform.
The clearance is usually less than 48”, and provides easy access to mechanical and utilities, as well as some storage potential. The crawl space may be open to the surrounding area or enclosed and often insulated to keep critters and the elements out. Currently, 15% of new construction in the U.S. has crawl spaces.
Slabs are essentially concrete floors upon which a structure is built. They don’t normally have a basement or storage underneath them and are ideal for passive solar homes and for radiant floor heating tubes. Electrical, plumbing, internet and communication lines, and tubes for central vacs are often buried or channeled beneath the slab to come up inside wall cavities. Concrete slab construction presently makes up about 54% of new construction in the U.S.
Slab construction may or may not have foundation walls. For unlevel ground, Concrete walls are formed and poured to provide a level perimeter. The inside is filled with engineered gravel and tamped down.
Mechanical and utilities are buried in the gravel, insulation and a vapor barrier placed down, and then the concrete poured. Radiant heating tubes and reinforcing may also be placed prior to the concrete floor. Slab-on-grade is also a slab, except it is built on well-packed leveled ground with proper drainage without perimeter walls, so is closer to the ground.
Cellar vs Basement vs Crawl Space
Cellars have existed longer than the other types of foundations. They were initially caves but more ‘modern’ cellars were built of stone or brick, commonly located fully underground, and often without windows. Without sunlight, the temperature stays steady and cool naturally.
Cellars were and are accessible from inside a structure or from separate exterior access. Ceiling clearance is typically between 4’ and 7’, although I’ve seen some wine cellars in Europe that are fully underground and exceed 30-feet in clearance!
A cellar may have floors of dirt, gravel, stone, concrete, wood, or a mix of materials. They may be located underground for ‘climate controlled’ storage such as a root or wine cellar, located under a building to raise it above the surrounding ground to provide a dry, level building platform, or located under a basement as a sub-basement for storage or safety. Most cellars were not built for daily living but for storage and security.
Basements are a more recent concept beginning in the 1950s. They are similar to cellars in that they provide a raised, level platform upon which to build a structure. However, they are commonly only partially underground and are designed for additional living space. So, they have a finished concrete floor, large windows, and clearances between 7’ and 10’. Older basements often have a windowless ‘cold cellar’ accessed off the basement and under the front or back entry, while modern basements seldom do.
Crawl spaces have probably existed for many millennia. They provide a raised level platform that is above surrounding ground levels, away from any water or dampness, and offer protection from insects, rodents, and other critters. Today, they are often used on sloped ground, low lands, wetlands, or those susceptible to seasonal storm surges or flooding. Crawl spaces also provide some storage and easy access to mechanical and utility services.
Can You Turn a Crawl Space Into a Basement?
Crawl spaces can be converted to basements in some situations, but professional assistance and a Structural Engineer are required. The structure needs to be lifted or moved to allow the ground beneath to be scrapped, excavated, or blasted to the desired depth.
Footings and foundation walls, and any support posts or walls placed and erected, utility and mechanical connections arranged, and the concrete floor poured. Drainage pipes laid, the exterior backfilled and sloped to prohibit moisture intrusion, the structure set onto and secured to the new foundation, and the floor and walls waterproofed, insulated, and finished. Not a typical weekend project.
What Is a Yankee Basement?
A Yankee basement typically began as a cellar under a house and was turned into a usable living space. A 2-1/2’ to 3’ shelf around the inside perimeter foundation walls was left, and the rest of the floor was dug out to provide the necessary clearances. The footings and foundation remained supported, and the interior living space significantly increased.
Can You Do Half Basement Half Crawl Space?
There are numerous houses with a basement and crawl space mix, and many reasons why builders combine them. In some situations, it’s to accommodate the slope and shape of the ground, others are for design purposes such as a split-level or to lower the profile elevation. It may also occur when building an addition.
The budget also can affect foundation decisions too. Blasting granite to make room for a full basement is more expensive than building a half basement and half crawl space arrangement. Additionally, if the slope of the land is such that part of a full basement will be fully underground without points of egress, building a crawl space under that half may be fiscally advantageous. As with most builds, a Structural Engineer’s input is recommended.
Which Is Better: Crawl Space or Basement?
Both crawl spaces and basements have their merits. Crawl spaces are better for uneven or wet ground, low laying areas, flood plains, and land subject to seasonal flooding or storm surges, so wherever water table concerns dictate.
Basements provide greater living, storage, and even rental income potential. Both foundation types raise the house above the surrounding ground, provide a level platform on which to build, and offer access to mechanical and utility services.
A basement offers a safe haven from hurricanes and tornadoes, greater storage space, and is less accessible to larger rodents and critters looking for a home. It is also within the heating and cooling envelope of the house, so is easier to control temperature and moisture. Additionally, basement footings and walls mark the structure’s location, so if there is ever a fire, the footprint ensures the structure can ‘usually’ be rebuilt in that same location.
The bottom line, if budget, topography, and water table permit, a basement has more to offer than a crawl space.