A potential 6-floor residential property has too many thin lally columns in the basement. Are they safe, and can they be fixed?

Thin, overloaded lally columns under a tall building can be a real problem, and yes, we can fix them. The repair is replacing or adding proper floor support, which runs $1,300 to $2,500 depending on how many posts and how much load they carry. Get a structural look before you buy that place.

Here is what is going on. A lally column is the steel post in your basement that holds up the beam, and the beam holds up the floors above. A six-floor building stacks a lot of weight onto a few posts down low. If those posts are thin, undersized, or there are too many doing the job of fewer correct ones, that is a sign the original support was patched together instead of engineered.

Thin does not always mean unsafe. Sometimes it just means cheap. But on a building this tall, we do not guess. The load path matters too much.

Signs the columns are struggling: a beam that sags in the middle, floors above that slope or bounce, posts that show rust at the base where they meet the floor, or a post that is not sitting on a real footing. Water at the base rots a post from the bottom up. If you see rust rings, that post has been wet.

What we do about it

We replace or reinforce the support. A few paths, and we pick based on the load.

Lally column replacement swaps a thin or rusted post for a correctly sized one on a proper footing. Floor support and power posts add capacity where a beam is carrying more than its posts can hold. For a building this size we may also call in helical or push piers if the trouble is the footing sinking under the post, not just the post itself.

We self-perform structural lifting and helical installs in-house, so one 603 crew owns the job start to finish.

You may not need all of it. If the posts are simply undersized but the footings are sound, swapping posts is the fix and we leave the rest alone. We will tell you that.

What drives the cost

Floor support work runs $1,300 to $2,500. The number moves with how many posts, how much weight each one carries, and whether the footing under it holds. Helical piers, if the footing is the real issue, run $2,700 per pier for the first three, then $2,200 per pier after that.

For a full foundation-wall rebuild or anything structural we have not seen yet, we price that after we see it. A six-floor building is not a standard single-family basement, so we want eyes on it before we put a number on paper.

One more thing on this one. 603 does repair, not new construction. If you are buying this property and the support needs to be re-engineered from the ground up, we fix and reinforce what is there. We do not pour you a new building.

A little NH framing

Up here, frost heave pushes on foundations and the soil around the footings is disturbed backfill, the looser fill that got put back when the place was built. Backfill drains slow and holds water, so the base of a post can stay damp longer than you would think. On a tall building, a post that loses its footing to a soft, wet base is the thing we watch for. If water is pooling at the floor wall joint near your posts, that base is wet.

The Insurance Information Institute notes that standard homeowners policies do not cover gradual foundation settling, so catching a support problem before you buy matters for your wallet, not just your safety. See iii.org. [verify]

What to do before you buy

Get a structural inspection. We do free inspections and free estimates, and you get your quote within 24 hours. We will measure the posts, check the footings, look at the beam, and tell you whether those thin columns are a real problem or just ugly steel that is doing its job fine.

Read more about our floor support options on our supplemental support and structural and foundation repair pages, and our helical pier work if the footings are the issue. Every fix we do is backed by the 603 guarantee.

Internal: structural and foundation repair · foundation repair · supplemental support · helical piers · sill replacement · the 603 guarantee

Ready to get it checked?

Call us at 603-610-1770 or book your free inspection. We will get a structural set of eyes on that basement before you sign anything.

Related questions

How do I know if a lally column is failing? Look for rust at the base, a beam that sags above it, floors that slope or bounce, or a post not set on a real footing. Water at the base is the big one. A wet post rots from the bottom. We check all of that on a free inspection.

Can you add support without replacing the whole foundation? Usually yes. Floor support and power posts add capacity, and lally column replacement swaps the bad posts, all without touching the foundation walls. Floor support runs $1,300 to $2,500. We only re-engineer the whole thing if the footings have failed.

Is the floor support work warrantied? Lally column and power-post work is backed for 10 years. Helical piers carry a 25-year engineered warranty. The transfer is conditional and voids if another contractor or homeowner touches our work.

Do thin lally columns always need replacing? No. Thin sometimes just means a smaller post that still meets the load. If the posts are sized right and the footings are sound, we leave them be and tell you so. We only replace what cannot carry the weight.