Maybe you went down into the crawl space yourself and came back up with a phone full of pictures you can't interpret. Maybe an inspector handed you a report full of words like pier, girder and column, and a photo of something under your floor that looks wrong.
Either way the question is the same. What are those crawl space support posts supposed to be doing, and does what you saw actually matter?
A crawl space support post is one link in a chain that runs from your floor down into the dirt: joists, a main beam, the posts under it, the piers they stand on, and the ground below all of that. Most of the trouble starts at the bottom of the chain rather than in the post you can see from the door.
The chain that holds your floor up
Every one of these parts hands the weight to the next one down. Knowing the order is most of what you need, because it tells you where to look when one room feels low.
Joists, the boards you see overhead
Lying on your back, the repeating boards running across above you are the joists, and your subfloor is nailed to their top edges. Joists carry the room, and they hand what they're carrying to whatever crosses underneath them.
The girder, which reports call the main beam
Somewhere below the joists, usually running the long way through the middle of the house, sits a larger member. Inspectors write girder. Crews say main beam. Either word describes the same thing: a heavy horizontal piece that gathers the load off many joists at once and concentrates it into a few spots.
Posts, columns and pilasters
Underneath the girder, at intervals, stand the pieces that hold it up. A wood one usually gets called a post. A masonry one gets called a column, and the crews here call a masonry column built into a wall line a pilaster. Anglin's field shorthand for the block version is CMU block column. All four words describe the same job.
Piers, pilings and footings
Each post stands on something. In older metro Atlanta houses that something is often a stack of brick or block, and under it a pad of concrete poured into the dirt. Reports say pier and footing. The owner here says pilings. The pad at the very bottom is the part carrying everything above it into the earth.
The ground it all ends in
Last link, and the only one nobody built. Whatever your pads are resting on has to stay put and stay dry, and when it doesn't, everything stacked on top of it goes down together.
Why the supports run down the middle of your house
Standing in the access door with a flashlight, the line of posts you're looking at is usually down the center, not around the edges. That isn't an accident, and it explains what's yours to worry about.
Your outside walls sit on the foundation, which carries that perimeter down to its own footings. The middle of the house has no wall under it, so the girder and its posts do that job instead. A room low in the middle of the house and a whole corner reading low outside are two different conversations with two different answers.
Which is also why a floor that slopes doesn't automatically mean a bad support. If you got here from a dip upstairs rather than from something you saw underneath, start with why floors sag instead.
Built right, or just worn out?
Here's the distinction that makes an inspection report readable, and it came from the owner in almost exactly these words. Some houses were put together in a way that was never going to hold. Others were fine, and the parts simply aged out: "it is built right, but the column itself is deteriorating."
The fix for the second one is smaller than people expect, because you're "replacing what was built good, it just deteriorated." Same sag upstairs, very different job underneath.
A support that wore out
Wood goes soft at the base, steel rusts through at the foot, brick and block lose their mortar and start shedding. Age plus moisture, with nothing wrong in how any of it was laid out. A house can run 30 or 40 years on original supports and then need one of them.
A support somebody added later
Find an adjustable steel screw jack under your beam and you've learned something useful: you're not the first person to notice this. Someone before you saw a low spot and propped it. Those jacks are made as temporary shoring, and the crews find them constantly. In the owner's words, "we also look in there where homeowners have hired handymen to put individual screw jacks that you can buy at Home Depot or Lowe's that are just temporary, that all have to come out."
Something that was never a support at all
Stacked loose blocks, a length of 4x4 standing on bare dirt, wood shims wedged into a gap at the top of a pier. None of those pieces were designed to carry a house for decades. Wood shims in particular are a spacer, not a structure, and finding a stack of them tells you somebody was closing a gap rather than fixing what opened it.
What the water did, and who handles it
Water is the single biggest reason supports under metro Atlanta houses stop working. It rots the wood ones, rusts the steel ones, softens the mortar in the brick ones, and washes the dirt out from under the pads all of them stand on.
The crews turn work down over it. Describing a house they'd walked the day before: "there was so much water being dumped in the crawl space that the footings that the CMU block columns were on were completely... looked like a Grand Canyon around."
So be clear about the boundary here, because it saves you a phone call. Anglin's does the structure: posts, beams, piers and footings. Keeping water out from under the house is a genuinely different trade, and a drainage company is who does it. New steel set into a crawl space that's still taking on water is money spent on the second problem before the first one. Get the water answered, then put the supports in.
What goes back in its place
Not much mystery to it. A failed masonry column or a rotted post comes out, and a steel post on a concrete pier under a proper beam goes in. Asked whether there's some other method, the answer was short: "The beam that we're talking about, and the footing and the post in place, is the one way."
The part worth understanding is why the new pier goes deeper rather than sitting where the old one sat. Whatever softened under the original pad is still soft, so a replacement set at that same depth inherits the same problem. What the repair is really buying you is a support that reaches ground that will hold. How that gets installed, what it runs and how long it takes are laid out on the crawl space repair page.
Sometimes nothing needs replacing
Worth saying, because the point of learning to read what's down there is being able to hear "this one is fine" and believe it. A customer who needed one thing and got a price for one thing:
"I needed a support beam added and they provided a very reasonable quote with no extras or pushy sales tactics."
Armin Samiei, 5 stars
Plenty of what looks alarming in a flashlight beam is a support doing its job while looking rough. Rust on the outside of a steel post is not the same as a post that has lost its footing, and a crumbling face on a brick pier is not the same as a pier that has dropped.
Frequently asked questions about crawl space support posts
What is a crawl space support post?
A vertical member standing between a pier and the main beam under your floor, carrying the weight of the rooms above down into the ground. Original ones in older metro Atlanta houses are usually wood or a masonry column. Replacements are steel, and they stand on a concrete pier rather than on soil.
How long should a support post last?
Indefinitely, as long as it stays dry and whatever it stands on stays put. A steel post under a dry crawl space is still fine at 40 years. The same post with water running past its base rusts at the foot, and a wood post in that spot goes soft, so the lifespan question is really a question about the ground it lives in.
Can I put in a support post myself?
People do, and the crews find the results under a lot of houses. The catch is that a jack or a post is only as good as the pier under it, and a support set on bare crawl space dirt presses into that dirt over time and gives the floor right back. Anything you put in yourself also needs to come back out before permanent supports go in.
Does a support post need concrete under it?
Yes, and that's the part homeowners skip. A post transfers the whole load of everything above it into a few square inches, and soil won't take that without spreading it out first. The pier and the pad below it exist to widen that footprint and carry it into ground firm enough to hold it.
Is a rusted steel post under my house a problem?
Surface rust on the shaft of a post is common and by itself means very little. What matters is the bottom few inches, where water collects and metal thins. A post losing material at its base, or one that's no longer sitting square on its pier, is telling you something about water down there as much as about the post.
My inspector wrote that a pier has settled. What does that mean?
The masonry stack itself is probably intact, and the pad underneath it has dropped into softer ground, taking the pier, the post and that stretch of beam down with it. Settled is a comment about the soil rather than about the brick. Expect the repair to go after what's below the pad, not just rebuild what's above it.
Find out what your floor is standing on
You shouldn't have to interpret a flashlight photo on your own, and you shouldn't have to pay to find out what it means. Someone can get under there, look at every post and what each one is standing on, and tell you plainly which ones are working and which ones aren't.
Anglin's has been under metro Atlanta houses since 1930.
Call 770-422-2924 for a free look.