Perma-Column® vs. Cast in Place vs. Wood in Ground: What Post Foundation System is Best?
Any building or post-frame structure is only as good as the foundation and column support system that keeps it standing tall. A failure where columns meet the ground means a failure for the entire building.
For complete transparency we at Farrow Built almost exclusively use Cast in Place columns, but the truth of the matter is, Cast in Place might not be the best option for you. This article will give you the pros and cons of three common methods of post frame foundation so you can decide what is best for you.
While it is possible to dig out old posts and reinstall them, no one wants to go through that hassle. You want a permanent no-hassle solution. But there’s more to consider than just strength and durability.
We’ll compare one new product and two traditional options. We’ll see how they stack up in terms of:
2. Strength & Durability
3. Ease of Installation
Perma-Column® is the new kid on the block. These highly engineered pre-cast columns come with integrated steel post brackets. They arrive on site ready to be placed in the ground and backfilled.
Cast-In-Place, or “poured-in-place”, simply refers to digging a hole to hold a form, pouring in a concrete mix, and setting a bracket on top.
Wood-In-Ground is the oldest and simplest way to get structural support. It is done by placing a pressure-treated post into the ground and backfilling.
If cost is your main driver, then dropping a pressure-treated wood post in the ground will always be the cheapest option. By forgoing concrete mixes and steel anchors the savings add up quickly.
Cast-In-Place comes in second in terms of cost. Concrete tubes, cement mix, and a bracket start at around $150 depending on the size of the post.
Perma-Columns® top the list, starting at around $200 or more per column. However, onsite labor is reduced due to not having to mix concrete and set brackets.
Winner: Wood-in-ground is the winner with a few caveats around durability and ease of installation.
#2. Strength & Durability
Wood-In-Ground. Wherever wood and soil meet, you’re bound to get decay. Placing chemically and pressure-treated posts directly into the earth might shorten the lifetime of your building. In exceptionally wet areas posts might rot out in as little as 10 years.
However, depending on the choice of wood and local climate conditions, you may get up to 40 years of solid support.
Another downside of wood posts is that they are not connected to footings. This leaves them vulnerable to vertical displacement in frost conditions.
Cast-In-Place supports offer tremendous strength and can last the life of the building. Wood that doesn’t touch the ground and isn’t exposed to the elements doesn’t rot. So long as the concrete column is poured correctly and to a sufficient height, this method is extremely long-lasting.
Because the footing and supports are poured at the same time, this method gains strength by having the two integrally bonded.
Perma-Columns® are made with rebar-reinforced, high-strength concrete. Since the concrete is cast in factory conditions, you can count on a premium mix. And. wood columns are kept at a safe distance from the ground.
Because Perma-Columns® are set on top of prefab footings, they lack the uplift resistance of Cast-In-Place columns. Vertical movement is a possibility.
Cast-In-Place gets the nod for the highest strength and durability with Perma-Columns® coming in a very close second. Both offer equal protection from the soil.. But cast in place provides better protection against vertical movement. Wood-In-Ground only provides the same decades-long protection under perfect circumstances.
#3. Ease of Installation and Time
Wood-In-Ground requires the fewest onsite tools and is faster than the other two methods. Other than pouring a footing there is no concrete required. No cement trucks and no mixers.
Despite the lack of complexity, setting posts in the ground take more skill and manpower than you would expect. Keeping 20’ tall posts plumb while backfilling requires muscle and finesse.
Cast-In-Place requires more tools and time than wood-in-ground.
Footings need to be poured, concrete tubes purchased and installed, and Redi-mix needs to be brought on-site. This means coordinating with the local concrete plant for deliveries or using mixers.
Once the pour is over, brackets need to be manually added to the wet mix and monitored for level. Then it’s 12-24 hours of curing time before posts can be added.
Despite their slim profile, Perma-Columns® are extremely heavy. They require a forklift to move around the job site and place in holes. Three workers plus equipment are needed to set and keep them plumb while backfilling.
Perma-Columns® can be delivered unassembled (anchor attached to concrete column) and ready to accept posts on-site. Or, they can show up pre-assembled with the precast columns already attached to wood columns.
Even in unassembled form, Perma-Columns® do away with the need for cement trucks. When combined with a composite footing pad no cement is needed at all. No cement means no mixing, pouring, or curing time. And, no curing cement means they can be installed in the winter and in wet conditions without worrying about tarps.
Winner: If time isn’t your main concern and the weather is cooperating, then Cast-In-Place wins for ease of installation. It requires the least amount of onsite labor. Keeping a sono tube plumb is much easier than an entire column. Most jobs have a cement plant nearby to pour when needed.
Cast-In-Place is a tried-and-true method for a reason. It is a winning combination of simple methods and widely available services and materials. The integrated footing and support column protect from movement and offers unbeatable strength.
If you have a reliable source of mixed concrete and can schedule in a day or two for curing, then Cast-In-Place is a solid choice that you won’t regret.
Perma-Columns® work well when you need a higher load-bearing capacity, you are installing where cement trucks can’t reach, or weather prevents cement pouring.
Wood in Ground is great if you are working with a smaller budget and need something put up quickly.