Remodel or tear down in Austin: the 50 percent decision

Last verified August 7, 2026 against the Austin Land Development Code · Kimbrough Gray · KiliGray Homes

An older Austin house is often noncomplying — legal when built, but not under today's rules. You may keep and modify it. Demolish more than 50 percent of its exterior walls and that protection ends, and the replacement is judged entirely against current setbacks, floor-to-area ratio and impervious cover. On a tight lot the new house can be smaller.

Applies to: Anyone buying or holding an older house in Austin and weighing a deep remodel against a teardown. Most relevant where the existing house sits closer to a lot line, or is larger, than today's rules would allow.

Why an old house is often worth more standing than gone

A lot of Austin's older housing stock is noncomplying: it met the rules when it was built, and would not meet today's. It might sit three feet from a side line where five is now required, or carry more floor area than Subchapter F would now allow.

That status is an asset. The house is not illegal, and you may keep it, maintain it and modify it. What you cannot do is knock it down and rebuild the same envelope — because the protection attaches to the structure, not to the land.

So the question is never simply "remodel or rebuild". It is: at what point does the work stop being a remodel in the eyes of the code? And Austin answers that with a number.

The 50 percent exterior wall rule is the fork. Demolish more than half of a noncomplying structure's exterior walls and it stops being a protected noncomplying structure. Everything you build after that is measured against the current code — not against what was there before. The full rule, including exactly how the 50 percent is measured, is on noncomplying structures.

What the replacement is then judged against

Once the protection is gone, the new house has to satisfy the current rules in full. For a typical SF-3 lot that means:

Setbacks — 25 ft front, 15 ft street side, 5 ft interior side, 10 ft rear. If the old house sat closer than any of these, that footprint is not available again. Setbacks.
Floor-to-area ratio — the greater of 0.4 or 2,300 sq ft under Subchapter F. An older house that exceeds this cannot be replicated. Floor-to-area ratio.
Impervious cover — 45% in SF-2 and SF-3, and the existing driveway, patio and pool all count. Impervious cover.
The setback plane — the "tent" shapes the upper floor in a way a 1960s house never had to deal with. The tent.

The uncomfortable arithmetic: on a lot where the existing house is generous relative to the modern rules, the legally permitted replacement can be smaller than what you demolished. That is the single most expensive surprise in this market, and it is discovered after closing far more often than before.

The order to check things, before you buy

Each of these can independently kill or reshape a teardown. They are cheapest to check in this order:

Which jurisdiction? Austin, or a separate city, or unincorporated — the rules are not the same and not all of them are Austin's. Which code applies.
Is the house 50 years old or more? That triggers historic review on the demolition permit, which is a program risk before it is a cost risk. Demolition.
What does the current envelope allow? Run the lot through setbacks, FAR and impervious cover as if it were vacant. That is your real ceiling.
What trees are on it? A protected or heritage tree and its critical root zone can remove a large part of the buildable area, and it cannot be negotiated away. Trees.
Is any use nonconforming? If the property carries a use that today's zoning would not permit, interrupting it for 90 consecutive days ends it permanently. Nonconforming uses.

Trees are the one most often missed. Setbacks and floor area are obvious on a survey. A protected tree's critical root zone is not drawn on anything you get at closing, and it can take a corner of the site out of play entirely. It is worth establishing before the offer, not after.

The case for staying under the threshold

Where the existing house is generously placed by modern standards, the most valuable thing on the lot may be its walls. Keeping enough of them to stay under the 50 percent threshold preserves a footprint the code would not grant again — and on a constrained lot that can be worth more than the convenience of starting clean.

This is a genuine engineering and cost question, not a loophole. Retaining walls that must then be worked around has its own price, and the measurement is exacting enough that it needs to be established on the drawings rather than judged on site. But it should be priced as an option before it is dismissed.

What this page will not do. It will not tell you whether your rebuild would be larger or smaller than what is there — that depends on the lot, the footprint, the district and the overlays, and any general answer would be invented. It also does not cover deed restrictions or HOA rules, which are private instruments, can be stricter than the code, and are not published anywhere we can verify. Both are questions for your survey, your title work and the city.

Common questions

Can I tear down and rebuild the same size house in Austin?

Not necessarily. If the existing house is noncomplying — legal when built but outside current rules — demolishing more than 50 percent of its exterior walls ends that protection, and the replacement must meet current setbacks, floor-to-area ratio and impervious cover. On some lots the permitted replacement is smaller than what was removed.

What is the 50 percent rule in Austin?

A limit on how much of a noncomplying structure's exterior walls you may demolish while keeping its noncomplying status. Cross it and the structure loses that protection, so the work is judged against the current code rather than against what was there.

Does a noncomplying house have to be brought up to code?

No. Noncomplying is not illegal. The structure complied when built, and you may keep, maintain and modify it. The constraint is on how much you may demolish before the protection ends.

What should I check before buying a teardown lot in Austin?

Which jurisdiction governs it, whether the house is 50 years old or more and so triggers historic review on the demolition permit, what the current setbacks, floor-to-area ratio and impervious cover would allow on the lot as if vacant, what protected trees and critical root zones sit on it, and whether any use on the property is nonconforming.

Do trees affect what I can build on an Austin teardown lot?

Substantially, and it is the item most often missed. A protected or heritage tree carries a critical root zone that can remove a meaningful part of the buildable area, and it is not shown on the documents a buyer typically sees before closing.

Before the code: our own read

Teardown or remodel: how the money actually decides it — Most owners ask this as an architecture question. We think it is a cost question, and the answer usually falls out of three numbers you can get in about a week.

Judgment, not code. Those pages carry no verification date and cite no ordinance — where they depend on a rule, they link back to these pages.

Send us an address and we will tell you what we find

We do this research ourselves on every project we take on — zoning, floodplain, watershed, trees, whether it is a legal lot. Send us an address and we will run it and tell you what we find. It works the same whether you own a vacant lot, a house you are thinking of adding a unit to, or a house you are thinking of replacing. No charge and no strings, and if it is a bad lot we will say so.

Send us an address

We are homebuilders, not the City of Austin. This page explains how we read the code in practice — it is not legal advice and it is not an official determination. Always confirm with Austin Development Services before you rely on it for a project. The authoritative text is the Austin Land Development Code; permitting questions go to Austin Development Services Department.