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Every property is structured on a foundation, but a solid foundation is necessary for a great home. With numerous options available, selecting the proper foundation is essential to build a long-lasting home.
One such option is the increasingly popular pier-and-beam foundation, commonly featured in contemporary residences. Its elevated design offers a set of traits that distinguish it from other foundation techniques and provide distinct advantages in specific circumstances.
But how exactly does a pier and beam foundation work? What should you anticipate if you select this foundation design for your house? And is it genuinely satisfactory?
In this post, we’ll discuss what a pier and beam foundation is, how to construct one, and the benefits and drawbacks of this type of foundation. We’ll also review its potential issues and expected building and repair costs.
Our objective is to give you all the information you need to make a well-informed choice on your foundation. So, without further ado, let’s get cracking!
What Is a Pier and Beam Foundation?
Pier and beam foundations are considered deep foundations and have existed for an extended period. Our forefathers utilized them as structural members for dwellings, sheds, barns, and other light constructions.
Unlike traditional dug-out foundations, the pier and beam are simpler, faster, less costly, and require lesser materials. They outlast structures built directly on the ground and are more stable overall. The crawl space beneath pier-and-beam foundations is usually 18 inches or taller to facilitate electrical and plumbing installations.
In those days, holes were bored through the soil’s soft or loose top layer to a more stable layer. They loaded these holes with flat stones to the required distance from the ground to create the ‘footing.’ On top of the piers, they installed wooden beams and leveled them to hold the structure and carry the load via the piers into the earth.
Today, these holes are typically drilled, and piers are fabricated from stackable prefabricated round or square pier slabs, concrete-filled sonotubes, concrete blocks, or other comparable concrete or masonry material. The beams are built from metal, wood, or concrete.
Traditionally, and even today, pier and beam foundations are utilized to create a level basis by elevating the building above the uneven terrain. They’re also used in areas where the soil lacks structural integrity or where the earth is vulnerable to seasonal moisture or flooding.
In other cases, a post is built above the pier to increase its height. The beam is then placed atop and attached to it. This assists in raising the structure for enhanced visibility above obstacles and protection against storm surges.
Piers are different from piles. For the latter, they’re pushed deep into the earth and depend on soil friction to avoid sinking.
Pier and Beam Foundation Design
A pier and beam foundation design starts after thoroughly examining the site’s terrain, soil-bearing capacity, and climatic concerns. You’ll also factor in the floor plan of the building it will hold and its intended function. The floor design and joist layout highlight key dimensions, structural elements, and possible plumbing issues.
The piers are typically positioned 5-10 feet in the middle around the perimeter. However, this can vary significantly based on the weight and size of the building. If you want it to hold the floor and structural components like the posts, the inside cavity of the building must be reinforced.
Choosing the pier’s shape, be it rectangular, square, or round, and the dimensions according to the building’s dimensions and weight is also essential during the design phase.
Some individuals prefer round piers in the middle of a building but rectangular or square ones at the corners. Typically, beams are sized to accommodate the joist framework of the construction.
Determining the size and distance between piers needs some arithmetic, which explains why numerous individuals delegate the task to an expert. Structures generally have a dead load of 10-20 per square foot (PSF) and a live loading of about 40PSF, giving a combined loading of 50-60PSF.
However, in certain places, ground snow loads of 70-90PSF substitute the live load number for structural safety, potentially increasing the total load to over 100PSF. After determining the cumulative load for your region, multiply the total area of your structure by that figure.
For instance, a cabin of 20 by 30 feet would have a load-bearing area of 600 square feet. Multiplied by a total load of 50PSF, the structure has a design weight of 30,000 pounds, even if its empty weight is approximately 6,000 pounds.
The total weight a single pier could support is determined by multiplying the pier’s horizontal contact area in sq ft by the soil’s load-bearing capacity in pounds. The smaller the number of necessary piers, the greater the horizontal surface and the better the soil capacity.
For instance, if you take the contact area of a 10 by 10ft pier, which is 100, then divide this value by 144 (the # of inches per square foot), it yields 0.694. This value is deemed as the exponential factor. If the soil load-bearing capacity is 3000 pounds, the pier can hold a weight of 3000 x 0.694, approximately 2,082 pounds.
If you’d like to determine the number of piers required for your design, divide the building’s weight by the maximum weight a single pier can bear.
For example, the 20 by 30 feet cabin with a projected load of 30,000 pounds divided by 2,082 pounds requires at least 15 piers. The spacing between piers is frequently determined by the tributary area and the supported load and is typically half this distance in all orientations. A 20 by 30 ft. cabin with 15 piers means that every pier has a tributary maximum of 40 square feet or roughly 8 by 5ft.
Most barns without floors are supported only at their perimeters, with intermediate piers used to hold dividing wall studs or loft posts. A 10 by 10 shed might have three piers on each side and one in the middle to hold the wall and floor beams.
A 20 by 20ft cabin with a deck might have perimeter walls reinforced every 5-8ft and a middle beam supported in this manner rather than constructing an arrangement of beams and piers every 5ft on the inside. It’s common for there to be fewer piers on a deck because its lighter weight and larger footprint reduce the need for heavy support.
After settling on the foundation’s size, the number of necessary piers, and their positioning, you’ll need to examine the site. A standard soil test can determine the load-bearing capacity of the soil. Nonetheless, any active moisture regions and expansive soils might demand a deeper pier, typically 5-6ft deep, to correctly anchor and hold the building.
Moreover, weather-related factors, like periodic flooding, wind loads, frost, and seismic considerations, could also be necessary. As the pier depth increases, so does the foundation’s security against shifting.
The construction and design of these piers are essential to the building’s stability. The piers could well be supported by either a 16″ x16″ x8″ (or greater) reinforced concrete pad or crushed stone.
Generally, the pad or gravel should extend beneath the frost line. The pier is subsequently poured or placed onto the footing pad and is usually rebar-reinforced.
The cross-sectional dimensions or diameter of piers span 6-16 inches and vary according to the load being supported. Typically, heavier loads require piers with 12 inches or greater diameter.
Bonus Tip: Observe all applicable codes and requirements while building a pier and beam foundation for any structure. If you have any doubts, hire a Structural Engineer, or verify your design with the area’s building department.
Pros and Cons of Pier and Beam Foundation
So, now that you understand what a pier and beam foundation is and what it takes to design one, is it appropriate for you? Here are some of the key advantages and drawbacks of this foundation to help you make an informed decision:
Here are the benefits of pier and beam foundations:
Protects Against Flooding
Pier and beam foundations raise buildings from the ground, making them less vulnerable to groundwater seepage and, thus, flooding. Pier-and-beam foundations could prevent water from getting into your dwelling in wetlands or on land downstream from substantial water bodies.
Cheap Repair Expenses
Though repair expenses vary based on the extent of the damage to your home’s foundation, pier and beam foundations are typically simpler and less costly to fix since you can more easily isolate the damaged section. The concept that pier and beam foundations raise homes above the ground tremendously aids in maintenance operations.
Easier Access to Wiring and Plumbing Work
The crawl space created by pier and beam foundations facilitates easier home maintenance and improvement projects. Compared to concrete slabs that embed plumbing work and electrical wiring into concrete, these foundations leave these pipes and wires in more open and accessible areas.
While most people don’t buy or construct a property with the idea that they’ll eventually uproot and relocate it, pier and beam construction makes that possibility a real one. By lifting the house above the ground, this foundation provides simple, unrestricted access to the underside of the home.
Flexibility for Irregular Land Plots
As housing construction grows deeper into the suburbs, away from flat, level areas, pier and beam foundations provide builders with greater flexibility to construct on slopes that aren’t level. If a location isn’t level, concrete foundations typically cause foundation concerns.
Reduced Excavation Expenses
Pier and beam foundations save time and effort during construction by reducing the depth construction workers must dig into the earth. Although this is generally true for slab foundations, the pier and beams demand considerably less excavation, making them a budget-friendly option.
Here are the downsides of pier and beam foundations:
Based on the climate and orientation of your home, the crawl space of a pier and beam foundation might become reasonably moist. Even if your home is safe from flooding because of its raised foundation, you must be vigilant and take any necessary procedures to drain moisture from it.
Dampness in your pier and beam foundation isn’t a primary concern compared to the rot that can develop with time. Therefore, there’s a risk that your home’s structure will fail, leaving you with tens of thousands of dollars in repairs to pay for.
Greater Likelihood of Pest Infestations
Sadly, the crawl spaces that pier and beam foundations make are ideal for insects, rodents, termites, and other pests who like to invade your residence. However, this shouldn’t deter you from contemplating this foundation for your home, mainly since there are many reliable do-it-yourself and expert options for eliminating pests.
Consider fastening or attaching the beams to support posts on your foundation piers if your house is located on a faultline or in an earthquake-prone region. Otherwise, your home could risk shifting in an earthquake or minor seismic activity. Repairing this level of damage becomes too expensive.
In colder climates, homeowners must be conscious of how cold air invading their crawl space could affect their home’s interior temperature. Although pier and beam foundations’ crawl spaces attract chilly air, you can address this problem by adding subflooring well above the structure’s skeleton.
How To Build a Pier and Beam Foundation
The construction of pier and beam foundations requires no heavy machinery and can be accomplished even by two persons. Here’s a step-by-step guide to how to go about building this foundation:
Step I: Leveling
Before bringing any materials to the construction site, you should determine your foundation’s placement and layout. In pier and beam construction, where you’ll need numerous individual piers, precise leveling is crucial. Any inaccuracies in leveling could result in costly structural damage to the house.
Step II: Digging
With the blueprints in place, the subsequent phase is digging the holes where you want to fix your piers. The ground conditions at the construction site will determine how deep you’ll have to dig out. Thus, some areas might require shallower holes than others and vice versa.
For extra support, one may choose to have a concrete slab laid at a shallower level into the foundation to act as the piers’ anchor. While the increased complexity does increase the total cost, it results in a significantly more stable structure.
Step III: Filling
After digging the holes, you’ll lower forms inside the holes and pour concrete to construct the foundation’s piers. As mentioned previously, leveling is essential for this foundation. Thus, you should keep the forms and concrete level throughout this procedure.
Then, you’ll install the beams’ mounting hardware before the concrete hardens for optimal bonding strength. The most used hardware is the simple metal L-bracket to secure wooden beams with screws and bolts. However, there are numerous other designs available with somewhat different functions.
Step IV: Mounting
After the concrete in the piers cures, you’ll fasten the wooden beams to the metal brackets mentioned above. Then, you can place and mount the timber subfloor frame to complete the construction of your pier and beam foundation.
Pier and Beam Foundation Problems
As with nearly every other foundation type, pier and beam foundations might encounter problems with time, particularly if they weren’t constructed correctly. Those constructed on firm ground with adequate maintenance and proper drainage could endure for decades. The primary structural issues are the cracking or settling of one or several piers.
Settling could result in bouncing or sagging flooring, stuck windows or doors, and rolling toys. However, settling is no primary concern, and you can address it by elevating it to a level position or stabilizing the surface beneath the pier.
Unlike most other foundation types, if your piers crumble or crack, you can easily replace them. If you fail to fix your piers and allow them to settle, they could tilt or shift, causing beams to slip and result in additional structural problems.
Other concerns with the pier and beam foundation result from incorrectly sealing the crawl space or poor drainage. These issues are akin to those of other crawlspace or basement foundations.
Inadequate ventilation, snow runoff, or rainwater accumulating beneath the structure could result in wood decay, mildew, and mold. Also, by leaving the crawlspace open, you invite animals like rats, raccoons, and insects into your home, which could result in additional concerns.
Pier and Beam Foundation Costs
Here’s a quick breakdown of the building and repair costs for pier and beam foundations.
The building costs for the pier and beam foundation are highly variable. Numerous factors come into play, including the number of piers your house requires, its condition, the state of the land, your locality, and the builder you select.
Nonetheless, based on the desired quality, a pier and beam foundation typically costs between $4-15 per square foot. This estimate generally includes the soil testing, excavation work, subflooring, and materials, including the anchor straps, beams, footing, and joists.
However, the crawl space that results from constructing a pier and beam foundation requires just as much care as the foundation itself. If you’d like to avoid the specific concerns associated with this foundation type, you could install vapor barriers, insulation, and other necessary features. These elements, though, come at an additional cost.
Interestingly, the additional building cost translates to lower maintenance and repair costs than basement and slab foundations. The explanation is that most of the building’s skeleton is deeply buried underground, leaving just the wooden anchor beams as the primary maintenance point.
A pier and beam foundation repair might range from $1,200-30,000. It all comes down to the nature of the damage being fixed. Pier and beam foundation repairs are labor-intensive and can necessitate working in a confined crawl space.
Here’s a look into the different repair types and costs for this foundation.
This repair only requires minor modifications. Occasionally, the joists or beams, which rest on the wooden beams, shift or become loose. To close any gaps, you’ll have to wedge and fix tiny wood pieces between the beams and piers. You can finish reshimming in a single day, often costing you between $1,200 and $ 7,500.
Adding New or Repairing Existing Piers
Piers can deteriorate with time and require reconstruction. Alternatively, a contractor may install additional piers to effectively support and disperse your home’s weight. Repairing or installing new piers might take up to two days and cost between $4,000-6,000.
Mold and rot can cause wooden beams (and the joists they support) to deteriorate with time; thus, they require replacement. The total cost depends on the number of beams that need replacement. Note that all wooden pieces are interconnected.
Therefore, if you want to repair a rotting beam, you must remove it from unaffected beams. Also, when repairing these beams, you’ll have to find other ways to sustain the structure. Due to these considerations, significant beam repair costs could vary from $10,000-20,000.
Support Jacks for the Crawl Space
With steel jacks, you could raise a weakened beam or joist back to the desired position. Based on the number of jacks you’ll need, this price could vary between $5,000 and $15,000.
Professionals will likely suggest underpinning when the piers around your home begin to collapse, and simple repairs won’t do the trick. Underpinning involves driving helical or push piles below the foundation until they reach more stable ground underneath.
Hydraulics then raise the foundation and level the house. Based on the number of helical or push piers you require, the cost could reach $30,000.
Remember, the costs associated with these services differ based on the extent of work required. Contact an experienced foundation repair expert to assess your property if you’d like a more precise cost breakdown.
Here are some of the most frequently asked questions on pier and beam foundations.
Is a pier and beam foundation good?
Pier-and-beam construction has numerous benefits, but the most common ones include increased safety against flooding, greater design freedom, and affordability. Additional benefits of this foundation include that it’s easier to maintain and ideal for irregular terrain.
Which is better, pier and beam or slab foundations?
Numerous things influence the preferred foundation type. A slab foundation is suitable for flat or relatively flat terrain, whereas pier and beam foundations are suitable for most terrain types. The latter also elevates the building from the ground and surrounding terrain, which safeguards it from flooding.
A slab foundation transfers vibrations to the ground at a significantly higher rate than a pier and beam design. This means slab foundations are perfect for areas prone to earthquakes. So, there’s ultimately no straightforward answer as to which foundation type is best; you decide what’s best according to your unique needs.
Is the pier and beam a permanent foundation?
Yes, most pier and beam foundations are permanent. They often rest on concrete, which is known to withstand environmental elements and other factors that may cause degradation. If you choose this foundation for your home, you are guaranteed up to 75 years of sustainability.
How long does a pier and beam foundation last?
Typically, pier and beam foundations survive approximately 75 years. However, other factors may impact the durability of the foundation. For instance, the building quality, materials used, and state of the surrounding soil can considerably affect your foundation’s longevity.
Should you insulate under a pier and beam house?
The crawl space underneath your home’s flooring allows heat to escape easily via the floors, affecting your home’s energy efficiency. Numerous homeowners opt to insulate their foundations to cut their energy bills and keep their cooling and heating systems from working excessively.