Front Porch Foundations
Essential to a Strong, Long Lasting PorchWe 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.
Footing, pier, and post foundation for front porchPorch 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.
Before Building Your Front PorchConsider the following:
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.
Types of Porch Foundations
Footings and Pier FoundationsThese 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.
FootingsFootings 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:
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 as this significantly increases post degradation due to moisture. You can avoid this problem and increase the longevity of your posts by using post bases as shown below.
Concrete Footing FormsConcrete footing forms like the Sakrete concrete form at right (available at Home Depot) are ideal for pouring concrete footings for porch foundations. They usually come in 4 foot lengths are are 8 inches in diameter.
Concrete forms 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 below, 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.
Pouring concrete into concrete footing forms
PiersLike 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.
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.
Diamond Pier Foundation SystemsHere'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!
PostsTypically, 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.e., placing my posts directly into or onto concrete.
Rather, I use adjustable mounting hardware (like the post base at right) to keep the two apart while simultaneously ensuring a solid connection.
Installing beam on posts and piers with post bases
Front Porch Slab FoundationsConcrete 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 concrete block foundation with stone
Pouring concrete over stone on front porch
Putting the final touches on the front porch concrete floorIf 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 being installed to receive concreteSee our concrete flooring section to see exactly how its done.
Perimeter FoundationsThese 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.
Ledger Boards - Integral to Your Porch FoundationUnless 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.
Ledger board installed under door thresholdAs with deck ledger boards, there are a few planning basics that are important to note about front porch foundation ledger boards:
We would be remiss if we didn't address a few porch foundation ledger board installation basics too:
Ledger board installation options
Know Your Local Building CodesLocal 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.
Ledger board supported by post and pier
Stand alone porch foundation
Video: How a Porch Floor is Constructed
Get Our Free Tutorial on Squaring Your Porch FoundationWe created a 14-page guide to help you get your deck or porch foundation square.
One of the most important factors to building a quality foundation is to be sure it is square to your home.
A square foundation makes the rest of the building process so much easier.
Sign up to get our step-by-step tutorial with helpful pictures, diagrams and a conversion chart for fractions to inches. We respect your privacy and will not share your email address.
Porch Flooring BeamsTraditional front porch floors are constructed a bit differently than decks. Whereas decking materials usually run horizontal to the home, porch flooring 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.
Front porch beam layout
Front porch joist layout
Front porch decking materials laid perpendicular to houseYou 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:
Porch and Deck Foundation PictorialPutting 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.
Water is the #1 Enemy of Your PorchThe best thing you can do to protect your porch is to prevent water from reaching it.
Porches need a solid foundation
See These TooWe 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.
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