By Dave and Mary
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Front Porch Foundations

Essential to a Strong, Long Lasting Porch

We normally don't think much about front porch foundations because usually they are not visible. But when it comes to foundations, what you can't see can hurt you.

I'm sure you've passed a house or two where the porch was literally falling off or sorely in need of porch repairs.

There could be several reasons for this but a poorly built foundation may be the major culprit.

Learn about footings and pier foundation for a front porch. Get our tips on building a good porch foundation.
Footing, pier, and post foundation for front porch
Porch foundations aren't that much different than foundations for homes. A foundation has to safely bear not only the weight of the porch substructure but also the roof, railings, columns, and more as well.

Download a free "How to Square Your Porch or Deck" ebook. Details below.

Consider These Before Building Your Front Porch

  • Geography and Soil Conditions: Where do you live? Unstable water or soil conditions may require deeper porch footings, thicker walls, or reinforced concrete. (Silty-clay soils, as an example, have an extremely poor load bearing capacity). In addition, if you live in areas with prominent frost heaves (which have tremendous force) footings must be placed below the frost line.

    Your specific soil condition can significantly impact the bearing capacity of your ground which is the amount of weight your soil can support your porch without falling down. The type, composition of the soil and moisture content, can all affect how much weight the ground can support. Soil with high bearing capacities may be needed to support larger or heavier porches.

    For example, soil with a high clay content usually has a higher bearing capacity when dry whereas it will have a lower bearing capacity when wet. Similarly, if your soil is mostly sand or gravel, it will have a higher bearing capacity than if it is mainly silt or clay. Also be aware of the presence of underground water or other subsurface conditions, such as rock or boulders.

    If there is any doubt about your soil condition, we recommend conducting a soil test to determine the specific soil conditions and bearing capacity for your porch before building a porch foundation. This should ensure that the foundation is adequate to support your porch.
  • Weight: How much does your porch structure weigh? The foundation must be strong enough to support its weight and the weight of your furniture and guests. We've all heard of accidents where a deck gave out because there were too many people on it.
  • Slopes: Foundation construction is also determined by the slope of the area. Flat areas or very slightly sloped areas, still need a good foundation. Even if you have a patio porch, the slab still needs to be stable. Any shifting of the roof can cause consider damage to the home.
  • In addition, regardless of the slope, always build to ensure water runs away from the structure. Soil structure is also important and will dictate how deep your footings need to be.

    For steep slopes, you will need either piers (columns of reinforced concrete) that sit on concrete slabs deep into the ground or perhaps even an engineered foundation.

Did You Know there are Different Types of Porch Foundations?

Learn the Lingo of Footings and Pier Foundations

These usually consist of short columns of either concrete block or poured concrete (piers) that rest on concrete pads called footings. Often these are poured as one unit. Typically, wood posts are then anchored to the piers which in turn support beams that are attached to the posts.

IMPORTANT: Although the process and structure of building a porch foundation is similar to that of a backyard deck, your porch's foundation will be carrying significantly more weight and must comply with your local building codes. Therefore, it is extremely important to understand what is involved to ensure your porch will be safe and maintain its structural integrity for years to come.


Footings carry the weight of the porch directly onto the soil. Depending on your specific geographical location, footings must be a minimum distance below grade to extend beyond the frost line and be sufficient in size to spread the load. The load includes the weight of your structure (known as the dead load) and people, furniture, and snow (known as the live load).

Don't let this intimidate you. In most cases, your local building codes department will be able to tell you the minimum requirements for footings which incorporate the load factors for your area.

When building footings consider the total weight they will carry. If you are planning to install heavy objects like hot tubs, stone fireplaces, etc., be sure to address this with your codes department or a construction engineer before you pour your footings.

Dimensions of piers, footing depth along with footing size, are determined based on geographical areas. I've found that 16 inch square footings (or up to 18 inch diameter footings) that are 8 inches thick to be fairly common. Check with your local building codes department.

Footing Details: Two typical footing and pier construction techniques:

diagrams of pier and footing construction

NOTE: Although this may be permissible by local building codes in some areas of the country; we do not recommend placing posts directly into concrete. Wood posts that are placed in concrete are at risk of rot and decay.

Over time, moisture is captured in the concrete and absorbed by the wood. This in turn causes post to decay and thereby compromises the integrity of the entire structure. Termites and other pests can burrow into the wood unseen and cause significant damage. There is also the possibility of concrete shifting over time which could cause structural instability.

We strongly using metal post brackets which will provide a stable connection between the posts and concrete and permit better drainage and ventilation. And lastly, exposed concrete is usually not aesthetically pleasing and can detract from an otherwise curb-appealing porch.

Concrete Footing Forms

Concrete footing forms like the Quikcrete® concrete form featured below are ideal for pouring concrete footings for porch foundations. They usually come in 4 foot lengths are come in 8, 10, or 12 inches in diameter.

pouring concrete footings and piers
Pouring concrete into concrete footing forms


Like decks, piers are an essential part of porch foundations. Piers are short concrete columns on top of footings that support posts. Piers, which are normally below grade, are meant to transfer porch loads to the footings.

In the photo below, footings and piers are poured simultaneously. Note a piece of sonotube is used to form the pier.

diagram of precast concrete pier for front porch Using a precast concrete pier (example at right) as part of your porch foundation is sometimes acceptable in geographical locations where there is little to no frost line.

Have You Heard of Diamond Pier Foundation Systems?

diamond pier foundation system platform Here's a novel way to install almost "instant" piers for your front porch or deck. No muss, no fuss, and you can start building the same day.

Learn about diamond pier foundation systems.

Posts - Why Not to Place Them in Concrete

Typically, posts are usually treated 4x4s, 4x6s, or 6x6s. As a general rule, concrete and wood don't mix so I almost always try to avoid mixing the two: I avoid placing my posts directly into or onto concrete.

Rather, I use adjustable mounting hardware to keep the two apart while simultaneously ensuring a solid connection.

concrete anchors for posts
Installing beam on posts and piers with post bases

Look at These to Make Your Job Easier

Mary and I discovered these products that we believe will make your foundation project easier to complete. We may receive a small commission on sales.

Concrete forms (referral link) are made of a lightweight fiber that you can use below and above ground for a one-time use. When the concrete has cured you merely strip away the tube.

I use them extensively because they are easy to square to ensure your footing is level. As you can see in the photo above, the entire footing is actually larger than the concrete footing form.

Your footing may need to be larger than the tube and in this case the tube is being used as both a footing and pier form.

A Simpler Way to Mix Concrete - No Mess; No Fuss!

If you are super excited to mix concrete in an old wheelbarrow, here's a better way to do it.

If He Can Do It So Can You

Obviously, you wouldn't want to do use Cement Solution Concrete Mixing Bags (referral link) for large areas but it is ideal for footings. It's reusable too.

If You Don't Like Mixing Concrete at All

Mixing concrete is often a time consuming and messy job; plus what do you do with leftover concrete? We found something that might make your concrete job even easier.

Quikset® Pro is an alternative to concrete that is a quick, light and durable resin footing compound that you can use for a wide variety of uses, from setting a mailbox to pouring footings.

At only 1.5 pounds, it equals two 55 pound bags of concrete - a back saver for sure! It's definitely something you should check out to see if it is right for your job.

Neat Way to Line Up Your Footings

Getting your footings lined up can be tricky at times. Here's a neat solution.

Plumbatube® (referral link)is a concrete alignment tool for concrete forms such as Quikrete® as well as other brands. They will fit both 8 inch 10 inch diameter tubes. They are graduated in degrees sufficient for a setup of 360 degrees if needed.

A Way to Reduce Moisture and Decay from Your Posts

Adjustable post bases (referral link) provide protection from moisture and potentially reduce decay. Use on footings to keep your wood piers from touching concrete which in many areas is required by local building codes. They come in 4x4, 4x6,or 6x6 sizes.

Front Porch Slab Foundations

Concrete front porch foundations usually consist of concrete poured at grade over a base material like stone or gravel.

Porch foundations from slabs don't have to be just at ground level. Concrete slabs can be poured at any height and offer many different finishing options.

If building a porch a few feet off the ground, concrete blocks are typically used to create the form. It is then filled with stone to within four inches of the top. Concrete is then poured on top.

filling front porch foundation with stone
Filling concrete block foundation with stone

pouring concrete over stone foundation on front porch
Pouring concrete over stone on front porch

smoothing front porch concrete flooring
Putting the final touches on the front porch concrete floor
If the porch is considerably higher, steel channels and steel sheathing panels are installed to height. Concrete is then poured over the steel sheathing.

steel channels and sheathing for concrete porch
Steel channels and sheathing being installed to receive concrete
See our concrete flooring section to see exactly how its done.

Perimeter Foundations

These usually consist of a continuous poured concrete footing supporting foundation walls that support the structure. They are often used where water is an issue or on steep slopes.

Quick Facts about Porch Foundations

  • Proper drainage is vital to a porch foundation. Foundations may need drainage channels or sloped surfaces to keep water away from them.
  • Porch foundations can affect your home's structural integrity. The reason is that porch foundations are often connected to your home, so they need to be secure and strong.
  • If you live in a cold climate, frost heaves can be a menace to porch foundations. When the soil repeatedly freezes and thaws, the ground may shift and cause damage to the foundation. In this case, your foundation may need deeper footings or other preventive measures. We recommend you consult a professional with experience in this area.

Know This: Why Ledger Boards Are Integral in Porch Foundations

Unless your porch is free-standing, you will need to attach it to your home. Like piers, ledger boards transfer the load from the structure directly onto the home's wall to which it is attached.

Just as important, they help displace the lateral load making for a substantially more stable porch.

deck ledger board mounted over brick wall
Ledger board installed under door threshold
As with deck ledger boards, there are a few planning basics that are important to note about front porch foundation ledger boards:

  • diagram showing ledger location The surface of your front porch should be lower than the interior floor leading on to it.

    To avoid a tripping hazard, the porch floor can be located just below the door threshold which will also make it easier to navigate with a wheelchair.

    For those who must contend with snow and ice, you should plan on your porch floor being at least four inches below the interior floor. Local building codes will probably dictate the distance.
  • To position the ledger board, consider both the distance from the interior floor and the thickness of your porch flooring material.
  • You ledger board should be the same size as your joist material.
  • Determine the length by subtracting 3 inches from the total width of your porch framing. This allows the end joists to overlap the ledger board. You may need to make the ledger even shorter if your porch flooring is going to overhang the porch framing.
  • Unlike decks, ledger board flashing for front porches may or may not be required. I; however, highly recommend flashing your ledger board even though it will be protected with your porch roof. It is inexpensive and easy to do. Check your local building codes to see if it is required in your area.

We would be remiss if we didn't address a few porch foundation ledger board installation basics too:

  • Most importantly, whether its a deck ledger board or front porch ledger, it must be attached through your home's sheathing and the rim joist with bolts or in some cases, lag screws. Your home's siding, brick veneer, or sheathing is not sufficiently substantial to hold your ledger board.
  • Building codes normally dictate bolt spacing. If they do not, a rule of thumb is to space 1/2 inch bolts at least every 14 inches with spans up to 10 feet; 10 inches for spans of up to 14 feet; and 8 inches for spans longer than 14 feet.

  • ledger board installation diagrams
    Ledger board installation options
  • Allow for drainage behind the ledger board by attaching washers to the bolt after it penetrates the ledger and before it is inserted through the sheathing.
  • If your home is constructed with I-joists or other kind of manufactured wood system, consult with your building department or a construction engineer.
  • If you have siding, you will have to mark and cut the siding in order to install the ledger board. Install flashing as indicated in the drawings above and caulk to create a weather tight seal.

Do You Know Your Local Building Codes?

Local building codes normally dictate your ledger board requirements. Many porch and deck failures are the result of poor ledger board installations. Therefore, in many locations, ledger boards must not only be attached to your home as indicated above but also supported by posts and footings as shown below.

Or, in some cases, porches or decks must be built as stand-alone structures as indicated below.

So be sure to check with your local building codes department before you start construction.

diagram showing ledger board supported by post and pier
Ledger board supported by post and pier

diagram showing porch with stand alone foundation
Stand alone porch foundation

Video: See How a Porch Floor is Constructed

Free Tutorial: Squaring Your Porch Foundation

Ebook cover -  14 page pdf showing how to square a porch or deck foundation Dave wrote a 14 page tutorial with tips for building a square porch or deck foundation.

When building a quality foundation, squaring it is important and this will make the rest of your project go more smoothly.

See Some Sample Pages and Get the Link to Our eBook

Sample of our 14 page pdf showing how to square a porch or deck foundation
Get our free tutorial here

Porch Flooring Beams - Not Exactly Like a Deck

Traditional front porch floors are constructed a bit differently than decks. Whereas decking materials usually run horizontal to the home, porch flooring traditionally runs perpendicular. Therefore, it is important to note that one or more additional beams are required.

As a general rule joists that are spaced 16 inches on center can extend 1 1/2 times in feet their width in inches. Thus:

a 2x8 can span to 12 feet (8 plus 4" (half of the width) = 12 feet)

a 2x10 can span 15 feet

a 2x12 can expand out to 18 feet.

However, this can vary by geographical area and sometimes by the type (or species) of wood you are using. Be sure to check with your local codes department.

I've included graphics below to illustrate how a porch foundation is typically constructed. Depending on the length of your porch, you may need to add an additional beam to carry the joists.

typical front porch beam construction graphic
Front porch beam layout

typical front porch joist construction graphic
Front porch joist layout

typical front porch flooring construction graphic
Front porch decking materials laid perpendicular to house
You must see our porch flooring section for additional details regarding hanging joists and adding your porch decking materials.

If you are considering building or replacing your existing front porch you owe it to yourself to check out this video courtesy of Vintage Woodworks - great must-know information!

Or watch it right here:

See Our Porch and Deck Foundation Pictorial

drilling holes for lag screws Putting up a porch foundation? Take a look at our porch and deck foundation pictorial to see how builders constructed a back porch foundation in six hours.

Know Your Porch's #1 Enemy

It's not birds nesting, though that may be a nuisance to some. The best thing you can do to protect your porch is to prevent water from reaching it.
  • Ensure you have adequate slope away from your home and porch to direct water away from it. If you have water issues, consider installing French drains, ensure your down spouts empty at least 10 feet from your porch, and add channels for water using crushed stone.
  • If you have a crawl space underneath your porch consider covering it with plastic to form a moisture barrier
  • Ensure your porch floor slopes slightly away from the house to direct water away
  • See our waterproofing tips for your porch floor - especially if you have a two story porch
  • Bevel hand railings
  • Use good primer paints and paint; keep up with porch repairs and maintenance
  • Ensure you have air access underneath your porch (use vents)

The importance of a solid porch foundation
Porches need a solid foundation

Before You Go...

beautiful deck with lighting and chairs

Take a Look at These Too

We encourage you to check out our other porch foundation information below and also other porch related subjects like our porch flooring or porch steps sections.

Mary and Dave, Founders of Front Porch Ideas and More
Hi! We're Mary and Dave, lifelong DIYers, high school sweethearts, and we both love porches. You've come to the right place for thousands of porch ideas.

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Mary and Dave, Founders of Front Porch Ideas and More
Hi! We're Mary and Dave, lifelong DIYers, high school sweethearts, and we both love porches. You've come to the right place for thousands of porch ideas.
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Use the PCA Visualizer to design your screen door

Shop for Porch Parts at Vintage Woodworks.

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We make no guarantees of accuracy or completeness of information on our site or any links to other websites contained here.

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