What Is a Crawlspace?

What Is a Crawlspace?

The crawl space is a traditional foundation construction in North America, Nordic countries, and Australia, and is becoming very popular in Central Europe too, especially for timber buildings.

It exists under the home like a basement, though it hasn’t the same height as a traditional basement. However, a crawl space is the middle ground between a basement and a simple foundation.

Crawl spaces tend to exist to provide access to ventilation and other systems beneath the home. Crawl spaces can be anywhere from one foot in height to more, though in order to qualify as a crawl space an adult should not be able to stand.


  • The investors usually appreciate lower investment cost and saving of time compared to the traditional slab-on-ground foundations.
  • Also antipathy to artificial materials like plastic foils or concrete sometimes plays a role.
  • The crawl space can be a relatively safe way for using natural thermal insulation (e.g. straw bales, wooden or hemp fibres) in the base floor.
  • In some cases, it is the best or even the only suitable solution for building foundation (e.g. sloping terrain).


  • many authors have reported major moisture problems in modern crawl spaces followed by mold growth and decay of building materials.


The base of a crawl space is the ground, which means that moisture-laden air is always present in the confined environment. Moisture condensation may occur and cause several housing problems.

For this reason, under-floor ventilation was originally designed to prevent excessive humidity, but under some conditions, it may have negative effects, such as an increase in relative humidity.

Can you dig out a crawl space?

The absolute answer is: yes, to make a crawl space for your house is an easy process, just by digging under your house floor. But is it really simple as i said? of course yes after asking an engineer and getting the permit to do that.

Real Statistics About Crawl Spaces

Houses with crawl spaces in the United States represent more than 21 million units from a total of 87 million single-unit structures (National Association of Home Builders, 2006).

Foundations of single-unit housing structures (excluding manufactured/ mobile homes) were classified in the 2007 American Housing Survey(U.S. Census Bureau, 2007) as: with a basement under all the building, with a basement under part of the building, with a crawl space, on a concrete slab, and others.

Insulating Crawl Spaces

Tools and Materials

  • Dust or respirator mask
  • work gloves
  • staple gun
  • batt or blanket insulation
  • heavy-duty staples
  • wire mesh


  1. Batts of fiberglass insulation should be installed in the bays between the floor joists.
  2. Staple wire mesh onto the joists to keep out animals and prevent the insulation from sagging.
  3. Staple fiberglass insulation batts onto knee walls above foundations. You can let the batts drape down over the masonry.

Crawl-Space Venting

Dirt floors require more ventilation than concrete floors. If the floor of a crawl space is concrete and the walls are insulated, you can ventilate with a series of small foundation vents.

The number of vents depends on the total square feet in a given space. A general rule is to have 1 square foot of vent area for every 150 square feet of floor space. Sliding metal vents are designed to replace the space of one 8 x 8 x 16-inch concrete block.

-A ventilated crawl space needs to be screened, with either pressure-treated-wood or PVC lattice and a welded wire netting.

-Plastic lattice provides venting in many shapes and colors—and when it gets dirty you just wash it down with a hose.

-PT (pressure-treated) lattice has a built-in resistance to water damage and rot, even near ground level.

-Use galvanized wire mesh or plastic screening to keep insects and animals from entering.

Crawl space Ventilated to Exterior

  1. Provide at least one square foot of net free ventilation area for every 150 square feet of crawlspace floor in a ventilated crawlspace. You may reduce the net free ventilation area to at least one square foot for every 1,500 square feet of crawlspace floor if you cover the floor with a vapor retarder such as six-mil polyethylene sheeting.
  2. Install covers such as screens or grates in the ventilation openings. Use screens, grates, grills, or plates with openings at least 1⁄8 inch and not more than ¼ inch.
  3. Subtract the space used by opening covers from the net free ventilation area of a ventilation opening. Example: a one square foot opening may be reduced to an effective 2⁄3 square foot opening when covered by a cast iron grill or grate. The cover manufacturer’s instructions should indicate the cover’s opening reduction amount.
  4. Locate a ventilation opening not more than three feet from every corner of the crawlspace wall. Unventilated crawlspaces are recommended by experts for most crawlspaces.
  5. There is considerable controversy about the effectiveness of crawlspace ventilation, particularly in warm humid climates. Check with a qualified energy efficiency professional before adding insulation between floor joists in crawlspaces. Check the condition of existing floor joist insulation in crawlspaces at least annually.

Unventilated Crawl Space

  • You may eliminate crawlspace ventilation openings by insulating the crawlspace walls or floor system as required by general codes and by installing all the following moisture control and ventilation components: (a) cover all exposed dirt in the crawlspace floor with an approved vapor retarder, such as six-mil polyethylene sheeting. (b) lap all vapor retarder seams by at least six inches and seal or tape the seams. (c) extend the vapor retarder at least six inches up the crawlspace wall and attach and seal the vapor retarder to the wall. (d) provide one of the following ventilation methods: continuous mechanical exhaust ventilation, or a conditioned air supply at a rate of 1 cubic foot per minute for every 50 square feet of crawl space floor area and provide a return air opening to the building interior.


Unventilated crawlspaces are recommended by experts for most crawlspaces.

  • Do not connect the return air opening for the building interior to a forced-air return duct. Use an opening in the floor or use an unpressurized duct between the crawl space and the building interior.
  • There is some controversy about providing conditioned air to a crawl space. Do not exceed the 1 cubic foot per minute conditioned air ventilation rate.

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Ultimate Myths to Solve Foundation Problems

Ultimate Myths to Solve Foundation Problems

Spotting Problems

A newer basement may have walls and ceilings that are solid and secure. Older basements often have problems that must be attended to. In some cases, the fixes are fairly quick and easy; in other cases, serious surgery is called for, which can be performed only by professionals.

If brick, stone, or block shows signs of surface deterioration, the problem is very possibly only deep. As long as the wall as a whole is plumb and free of bulges or indentations and the floor above is not sinking, damage like this can be fixed by filling in with mortar.

Problems with basement walls and floors— often called a house’s foundation—are visible not only in the basement itself but also on upper floors, as shown in the drawing. When these problems manifest themselves, you should take steps to fix them in a timely manner, or they can get worse and damage the rest of your home. They certainly should be repaired and shored up before attempting any basement remodeling—which can often cover up the problem, so it grows worse when out of sight. In general, look for cracks that are wider than 1⁄4 in. or that are offset. Also, see if your walls or floors are uneven.

If cracks in a basement wall are uneven or offset, like those shown here, there could well be a problem with the underlying concrete or stone footing. This problem will not fix itself and is likely to get worse. Has it looked at by a professional?

The drawing shows other signs of structural problems. If a chimney leans so it pulls away from the house at the top, the problem may simply be with the chimney. Or, it could be that the foundation it rests on is sinking or leaning. This can lead to damage to your house’s siding and even its structure.

WARNING: If a floor has a crack wider than 1⁄4 in., or if it is uneven so that one area is more than 1⁄2 in. higher or lower than an area less than 8 ft. away, the basement floor is likely in trouble. However, unless the floor is separating from the wall, the problem can often be solved by reinforcing the floor, perhaps by adding another layer of concrete. Or, you may need to break out the old concrete and pour a new floor.

Crumbling and falling ceilings

Older basements with lath-and-plaster ceilings often end up looking something like the photo at right. If the damage is not severe, you may be able to “skin over” the ceiling by attaching sheets of drywall that hold the old material in place. However, if it looks like this or worse, you should remove the plaster and the lath—an extremely messy process, so wear a respirator and ventilate the basement with outward-pointed fans as you work.

Old plaster often fails in a basement. Depending on the amount of damage, you may repair, replace, or cover over it.

Bowed walls are a sure sign of trouble. Hold a 6-ft. or 8-ft. level against the walls at a number of places. The walls should be reasonably plumb (though they do not have to be perfect), and they should be straight. If you see a bulge, or if a wall is out of plumb by more than half the level’s bubble, call in a basement expert for assessment.

If you see gaps under baseboards—either in the basement or on the first floor—that means the floors are sinking, which most likely means that the house’s footing is sinking. If the gap is more than an inch, the problem could be serious, and you should have the house’s footings inspected.

If windows or doors in the basement or on the floor above are noticeably out of square, they will not close properly. The problem could be that the house’s foundation is sinking in some places. You could reinstall the windows or doors, using shims to keep them square, but the underlying problem may remain and get worse. The foundation likely needs to be fixed.

If cracks like this near a window develop on the first or second floor of the house, have the foundation inspected. This is often a sign of a sinking footing.

Solving Foundation Problems

Unfortunately, foundation repairs are not do-it-yourself projects. Find a company with a long history of foundation repair in your area. The company should have plenty of references you can call, and the salesperson should explain clearly the type of work they will do. Two common repairs are adding carbon armor straps and neckties.

If a wall is bowing in the middle due to soil pressure, the bowing can often be stopped with the installation of special foundation straps that are typically made of super-strong carbon fiber. These can be installed quickly and on the inside of the basement, so no excavation is required. They can be painted over or hidden behind walls that you frame out.

If an entire wall is leaning at its top, the process can be stopped by the use of a foundation strap with the addition of a necktie. Made of exceptionally strong Kevlar® or fiberglass, a necktie is bolted with special hardware to the outside or rim joist, to hold the wall in place.

If the floor is sinking, the foundation likely needs to be raised and reinforced. A basement repair company can insert foundation piers.

A carbon strap won’t fix a bowed wall, but it will stop the wall from continuing to bow. The strap—and bowed wall—can be hidden behind drywall.

A floor that is 11⁄2 in. below the bottom of the wall (left) has sunk and needs to be raised and reinforced. After raising the foundation with a foundation pier and supporting it by pumping in concrete, as shown on, the floor is brought up to meet the wall and will not sink any farther (right).


Straps and neckties stabilize walls that lean slightly. But if a wall is leaning or bowed seriously, and you need not just to keep it from getting worse but to actually move it into a better position, then solutions from the outside are called for. A wall anchor system can be installed with surprisingly little disruption to your yard.

With almost surgical precision, heavy-duty wall anchors are inserted into the soil and secured with threaded steel rods that poke into the basement. Inside, you see a series of wall plates. Bolt heads on the plates can be turned to adjust the wall’s position.

Installing wall anchors

Companies that specialize in repairing bowed and damaged basement walls have developed methods to limit the damage to interior walls and the lawn outside. Here are some techniques used by the Perma-Seal company in the Midwest. There are likely companies in other areas that follow this or a similar technique.

  • Using heavy-duty drills and massively long masonry drill bits, holes driven through the interior wall are generally only 2 in. or so in diameter.
  • Through experience and some calculating, the workers know pretty much where the drill bits will end up on the outside. Holes are dug from those locations.
  • Here, I see that the sod is neatly cut out so it can be replaced later. Large threaded rods are pushed through the hole in the interior wall to the outside holes, where they are attached to wide plates.
  • From the inside, the threaded rod’s hole is filled with a very strong epoxy that keeps out any possibility of moisture infiltration.
  • A large plate is attached temporarily while the wall is ratcheted back into straight vertical.
  • The plate is left in place. It may need adjusting in the future. You may leave it exposed, or cover with framing and drywall.

Foundation Piers

If your walls and floors are sinking, the concrete footing they rest on is likely sinking. Believe it or not, footings can be raised. However, this is the most extreme repair, involving digging a wide trench around the house, inserting a steel push pier deep into the ground next to it, and raising the footing up with steel brackets attached to the pier.

The process can take some days, as the footing is raised slowly with hydraulic pressure. Once raised, concrete is pumped into space under the footing, and the house will remain stable for a century or more to come.

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Plan basement Layouts and Installations

Plan basement Layouts and Installations

Minimalist Approaches

The most common approach to basement remodeling includes installing flooring, wall, and ceiling surfaces that look very much like those in upstairs rooms. We are creatures of habit, comfortable when surrounded with smooth walls covered with paint, paneling, or tile, as well as floors that are tile, hardwood, or carpet.

But there’s another way of thinking about a basement: It need not be like all the other rooms in the house, and may actually have a sort of rustic (or industrial or Bohemian) charm if treated more lightly. The idea is to “let a basement be a basement.” Once you achieve this attitude, all sorts of funky elements—pipes, ducts, exposed joists and beams, rough masonry walls and floors, and even some appliances—no longer appear as eyesores. Instead, they achieve (in one’s mind, anyway) the status of “utilitarian beauty.”

In this basement, a hardwood floor was laid, but the walls were simply spray painted; ceiling joists are left exposed, and electrical supplies are on display. Rather than hiding large ducts, they are celebrated for their shininess. Overhead canister lights are also left exposed, as is the wiring leading to them. A wall of glass block adds to a Euro style.

Perhaps the greatest virtue of the minimalist approach is that it can save tons of money. Moving pipes and ducts, framing walls and floors, and installing drywall surfaces, as well as finished-looking lights and plumbing services, consumes lots and lots of time and materials. And, in many cases, such hardcore remodeling is strictly cosmetic and does not actually make a basement more comfortable or usable. Plus, strategies like leaving walls and floors unfinished or merely painted ensure against expensive damage in case of a flood.

All that money you save can go toward things that make a basement memorable, such as artwork for walls, fancy rugs, and fun stuff like a pool table or wine cellar. However, do not neglect safety and comfort concerns. If you have nonmetallic cable for wiring, it should not be in easy reach. Perhaps replace it with solid conduit , or cover it up with a simple frame and drywall or paneling. And if your walls and floors get very cold, you may choose to insulate and seal them up. Window and exterior door replacement may also be a good idea.

Even exposed black steel gas pipe can be appealing, especially if it is neatly installed and clean. Here, the excess pipe dope or Teflon® tape has been carefully removed.

Often the minimalist approach involves spray-painting walls and ceilings (including pipes). If a concrete floor is relatively uniform in appearance, acid staining may look great. If it varies in texture and has other imperfections, consider simply painting it.

Layout Considerations

Getting Ready

Before you start planning room types and sizes, open up your space by clearing out all unnecessary stuff-including all those storage items that you can put elsewhere. Take steps to ensure that space is dry and will stay dry, as discussed previously. If your basement is riddled with posts, or your large appliances are sitting in the middle of the basement, planning around these obstructions can be complicated and frustrating. You may want to install new beams and remove posts to give you a clean slate on which you can make your plans.

Keeping Clean

Doing construction work in a basement can be dirty and dusty, so one of the first orders of business is to figure out how to handle the mess. It has been said that the first tool a remodeler should buy is a high-quality Shop-Vac® with a really good collection system. You may not opt for the high-end setup shown below, but at least get a large-capacity vacuum with a HEPA filter and plenty of dust collection bags. Plan to clean often—at the least, at the end of every workday.

A great dust collection system often starts with a high-quality shop vacuum. But even if you have a standard Shop-Vac, the addition of a secondary unit, like Oneida’s Dust Deputy® will greatly increase its efficiency. This unit spins dust cyclonically and removes most of the dust even before it reaches the vacuum.

As much as weather permits, open windows and put outward-facing fans in them. Simple inexpensive box fans can do a remarkably good job of lessening or eliminating airborne particles.

Safety Alert: Before removing a basement wall, be sure it is not load bearing. A bearing wall runs perpendicular to the joists in the basement ceiling and supports them where needed.
If you want to remove a bearing wall, you will need to replace it with a beam that is approved by your building department as strong enough.

Construction dust—and especially drywall dust—has an amazing ability to seep through even tiny cracks and infiltrate other rooms. How it travels upwards we may never know, but it does. Whenever possible, use plastic sheeting and tape to seal off areas of the house not being worked on.

You can prevent marital and familial hard feelings by carefully taping off “innocent” rooms that are not involved in the construction. It can be an annoyance to keep these areas sealed every day, but it’s well worth the effort: Cleaning infiltrated dust can be a major job in itself.

Working with Your Building Department

Local building codes cover many operations you may perform while remodeling a basement, from structural support to insulation of outside walls, electrical and plumbing installations and more. Though your basement may seem out of sight, it is recommended that you consult with your local building department before starting work. Building codes may seem strict, but they are designed to keep your basement safe and secure.

You will probably need to schedule inspections of various types at various stages of work, for instance:
framing, rough electrical, rough plumbing, finish electrical and finish plumbing. The building department may require that some of the work be performed by a licensed electrician or plumber.

If you’re tempted to skip the building department, keep in mind that when you go to sell your home you could get into trouble. And if you are caught working without permits, the inspector may make you tear up walls or the floor to uncover the work they need to inspect—a very expensive and diffi cult proposition.

Planning and Drawing

Use a computer program or just a pencil, graph paper, and straightedge to plan your room(s). Start by carefully measuring your available space. Make a scaled drawing of the empty space— including all the little obstructions and bump-outs—and make a number of copies, so you can sketch onto them.

Overall Plan

An overall plan shows where all the stuff goes. Be sure to take into account the full thickness of walls—which may be as thick as 8 in. around the perimeter, depending on how you construct them. Also include doors (and the way they swing), windows, major appliances, shelving units, and bathroom fixtures.

Make an overall plan view (top view) drawing, showing where all the important things go. A family room may have wide open spaces, so you can later put in a pool table or exercise equipment. A bathroom and utility room, on the other hand, have elements that need to be precisely planned.

Individual Plans

Also make detailed drawings of the bathroom, utility room, laundry room, and any other room where the precise placing of appliances and fixtures is important. In addition to a plan view drawing, side views (elevations) help you visualize the final look.

Laundry room

A side-view drawing—either computer generated like this one or drawn by hand—helps you gain a greater feel for how spacious or cramped the folding table, shelving, and other elements will be.

Bathroom Plan

This bathroom plan-view drawing includes not only the toilet, sink, and shower unit but also a towel bar, a niche in a shower wall, and recessed medicine cabinets. Precise dimensions help to place elements where they will be comfortable to use without wasting space.

Bath Elevation

This elevation-view bathroom drawing is so detailed that it shows the shower tiles to scale, to get a complete feel of the room.

Electrical Plan

Also make an electrical plan showing the locations of light fixtures, switches, and receptacles.

Drowing Symbols

Architects and builders use many symbols to represent various elements in rooms. Here are some of them.

Working With Subcontractors

Plumbers, electricians, drywallers, framers, and other tradesmen all can do their work faster than you can—unless you are one of them. You no doubt want to save money by doing much of your own work. But even professional contractors often hire “subs” because it just makes things go more smoothly.


You can be the general contractor on the job, or you can hire someone else to do that. If you hire, say, a plumber to run the rough plumbing or drywallers to hang and finish the drywall, they are your subcontractors. Be clear on which permits you need to pull and which they need to. Plumbers and electricians usually pull their own permits and are present for the inspections.

Bids and The Contracts

You may have heard that you should get three bids on a job and go for the one in the middle. That’s not always true, but it often is. Don’t just shop around for the cheapest price, or you may get shoddy work. Vet the subcontractors: Take the time to ask around and find out if a sub is reliable, if his work stands the test of time, and if he will do the job when you want it done. Many subs do good work but take on so much work that they may be weeks late in getting to your job. The contract does not need to be elaborate, but it should specify:

  • The exact materials to be used, including brand names.
  • A payment schedule that holds back a significant sum until you are completely satisfied with the work and it has been inspected and approved.
  • Which materials they will supply and which you will. For example, you may provide the sink, toilet, tub, and light fixtures, and subs may provide pipes, cables, and all the behind-the-walls stuff.
  • A schedule of when things should be finished, and penalties if work is not done in a timely manner. This does not have to be punitive and unfriendly, but if the sub is weeks late, he should feel a wallet pinch.
  • A statement of who will actually do the work. You don’t want the sub to sub-sub it out to someone you don’t know.

The Order Of Work

To keep the job going at a reasonable pace, start out with a loose schedule of when things will happen. In general, a basement job follows this path:

  1. Making repairs to the concrete surfaces, and taking steps to ensure dryness
  2. Moving large appliances and heating units, if needed
  3. Lowering the floor and/or moving up pipes and ductwork, if needed
  4. Getting permits
  5. Making structural repairs and installations, such as to beams and posts
  6. Insulating the exterior walls
  7. Framing exterior and interior walls
  8. HVAC installations
  9. Rough plumbing
  10. Rough electrical
  11. Insulating between studs, if any
  12. Installing windows
  13. Hanging and finishing drywall
  14. Installing doors
  15. Finish carpentry—trimming doors, windows, and base
  16. Painting and staining
  17. Installing subflooring and flooring
  18. Finish plumbing
  19. Finish electrical
  20. Installing bathroom accessories
  21. Installing door handles, thresholds, and transition strips; paint touchup
Evaluating a Basement

Evaluating a Basement

While it’s impractical to add headroom in a basement, there are some ways of working around the requirements.You can often move Ducts and pipes, and beams and other obstructions can be incorporated into walls or hidden in closets or other uninhabitable spaces. Also, some codes permit lower ceiling heights in rooms with specific purposes such as recreation rooms. If headroom is a problem, talk to the local building department before you give up on your dream room.

A well-built basement is structurally sound and provides plenty of support for finished space, but before you cover up the walls, floor, and ceiling, check for potential problems. Inspect the masonry carefully. Large cracks may indicate a shifting around the foundation; severely bowed or out-of-plumb walls may be structurally unsound. Small cracks usually cause moisture problems rather than structural woes, but they should be sealed to prevent further cracking.

Contact an engineer or foundation contractor for help with foundation problems. If you have an older home, you may find sagging floor joists overhead or rotted wood posts or beams; any defective wood framing will have to be reinforced or replaced.

Understanding My Basement

Basement Anatomy

To ensure that your basement will be secure and dry, start by gaining an understanding of how it was constructed. The drawing below shows a fairly typical construction for a basement, plus framing for the floor above. Poured concrete walls (or walls made of block or stone), which are often 8 in. or 10 in. thick, rest on concrete footings that are often 10 in. thick and reinforced with steel.

A poured concrete floor is often 3 in. or 4 in. thick and reinforced with metal. If the concrete walls, footings, or floor are not strong enough, or if they rest on soil that is not firm, then walls and floors can sag. Here drainpipe (often referred to as “drain tile”) runs around the exterior of the house at the bottom of the wall. The pipe is encased in gravel, so seeping water can easily enter the drainpipe and flow away from the basement.

If a basement does not have this drainpipe, it should have tile running under the basement floor on the inside. The tile should run into a sump pump. In this example, there is a massive beam running through the center of the basement ceiling, to support the joists (which are ceiling joists for the basement and floor joists for the first floor).

The beam is supported with large posts, which rest on deep concrete footings. This beam is often needed if the width of the basement is too long for joists to span and remain strong. However, if the basement is not very wide, or if engineered joists are used, then the beam may not be needed. During a remodel, the posts are often removed. In order to do this, the wooden beam is replaced with a very strong steel I-beam, which can span very long distances. A “bearing” wall can take the place of a massive beam but will limit floor-plan options. A “curtain” wall is not needed for support and can be removed.

The joists (which again serve as floor joists for the first floor and ceiling joists for the basement) rest on a sill, which rests on top of the basement wall. This sill should be made of pressure-treated or other rotresistant lumber. The rim joist, which rests on the sill and runs around the room, should be carefully protected from moisture with building paper and siding.

In this example, one side of the basement has outside soil grade near the height of the basement wall. The other side is a walk-out basement, with the outside grade at floor level. Many basements have walls that rise above grade by a couple of feet or more. In that case, windows can allow light in, and the basement is said to be at “garden” level.

Wall And Footing Materials

Most basements built after World War II have walls made of poured concrete or concrete block. Basement walls in older homes may be stone, at least at their bottom 4 ft. or so, and perhaps brick or block atop the stone.

Poured concrete

Poured concrete walls usually present a fairly monolithic surface. At their bottoms they rest on a poured concrete footing, which is typically 4 in. or so thicker than the walls.

If they were poured correctly, with metal reinforcing bar (called rebar in the trades), concrete walls will be very strong. And if a solid waterproof coating was applied to the outside of the walls before they were backfilled with soil, the walls should successfully resist water infiltration, unless hydrostatic pressure is very strong (see p. 28). However, some concrete walls were poured or reinforced incorrectly, and this can lead to moisture and structural problems, as the following pages show.

Concrete block

Often referred to as “cinder blocks,” structural blocks are actually made of concrete poured into molds. They are typically 8 in. wide by 16 in. long, with open spaces called “cells” inside.

The blocks are stacked on top of each other in a running bond pattern (which means each block rests on two blocks below, rather than just being stacked in vertical rows).

Block basement walls usually rest on a poured concrete footing. For strength, the walls should be reinforced in three ways, as shown in the drawing: with horizontal ladder-type reinforcing mesh every two or three courses; by filling at least some of the cells with grout (which is actually a type of concrete); and with vertical rebar embedded in the grout fill every other block or so.

Unfortunately, not all block walls are created equal, and some lack sufficient reinforcement-making them susceptible to cracks that need to be sealed and perhaps repaired as well.

Many older homes have a foundation and a lower wall made of natural stone assembled with mortar joints. Many of these walls remain strong and level for centuries because of their massive size (often 2 ft. thick), the durability of boulders, and the old-world skills used in their construction. Often, a brick wall is installed on top of the stone wall.

These walls were likely installed in the days when people didn’t think of living in their basements, and so they may not be very waterproof. Some can stay surprisingly dry, but inspect yours carefully after a heavy rainfall for any signs of moisture. If moisture is a problem, consider having the outside of the wall waterproofed.

In this older home, mortared stones were used to make a footing and about 3 vertical feet of wall. If your house has a wall like this and the mortar between the stones is eroding, the wall has likely been exposed to moisture.

Most brick homes built before World War II were constructed so that the bricks actually form the structure of the house. (Most brick homes built more recently use brick only as a veneer; the foundation and basement walls are most likely poured concrete, and the house’s structure is made of wood.) Usually, the basement wall is three wythes, or thicknesses, of brick. There is typically little if any metal reinforcement. Instead, the bricks are laid in an interlocking pattern. The brick wall is shown here, which rests on a stone foundation, was built in 1882. Its walls are almost perfectly plumb, and it is, overall, no more than 1⁄4 in. out of level.

How to Evaluate Your Basement

Your basement’s mechanicals is another important consideration. The locations of water heaters, pipes, wiring, circuit boxes, furnaces, and ductwork can have a significant impact on the cost and difficulty of your project. Can you plan around components or will they have to be moved? Is there enough headroom to install a suspended ceiling so mechanicals can remain accessible? Or, will you have to reroute pipes and ducts to increase headroom? Electricians and Heating Ventilation and Air Conditioning (HVAC) contractors can assess your systems and suggest modifications.

  • Trace plumbing lines and note locations of shutoff valves on supply lines, which are natural points for adding new pipes or redirecting old pipes. If you are considering a bathroom or kitchen addition, also trace drain lines back to the main drain stack, and take measurements to determine if adding new drain lines is feasible.
  • Evaluate headroom in your basement, paying particular attention to ductwork that is mounted below the bottoms of the floor joists. In many cases, you can reroute the ductwork so it runs in the joist cavity.
  • Look for asbestos insulation, usually found on hot air supply ducts from the furnace. Asbestos removal is dangerous and closely regulated, but it in many cases you can do it yourself if you follow the right prescriptionsè. Check with your local building department or waste management authority for more information on asbestos abatement in your area.
  • Identify sources of standing water and visible leaks. If water comes into the basement on a regular basis through the foundation walls or floor, you’ll definitely need to correct the problem before you begin your basement project.
  • Inspect foundation wall cracks to see if they are stable. Draw marks across the crack and take measurements at the marks. Compare measurements for a few months to see if the crack is widening. If the crack is stable you can repair it. If it is moving, contact a structural engineer and resolve the problem before you begin your remodeling project.
  • Probe small cracks in poured concrete walls and floors with a cold chisel to evaluate the condition of the concrete. If the concrete flakes off easily, keep probing until you get to solid concrete. If the crack and loose material extend more than 1″ or so into the wall, contact a structural engineer.
  • Check the mortar joints on concrete block foundation walls. Some degradation is normal, but if gaps wider than 1/4″ have formed, you should have the wall repaired before you begin building.
  • Check for bowing in basement walls. Water pressure in the ground often causes concrete walls to bow inward over time. As long as the amount of bowing is less than 1 or 2″ and the bowing is not active, you can usually address the problem by furring out from the wall with a framed wall.
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