---
title: "What Is Substantial improvement? Building Glossary"
description: "Substantial improvement means a rebuild or addition costing 50 percent or more of a building's market value, which requires the whole building to meet current..."
url: https://build813.multisites.ai/glossary/substantial-improvement
publisher: Halo Homes
phone: +1-813-956-1972
quote: https://build813.multisites.ai/contact
---

![Two-story white modern home with black windows under oak trees and palms](https://build813.multisites.ai/_astro/night-front.CcvWPu3t_ZtnzXn.avif)

# Substantial improvement

Substantial improvement means a rebuild or addition costing 50 percent or more of a building's market value, which requires the whole building to meet current flood rules.

FEMA defines substantial improvement as any reconstruction, rehabilitation, addition or other improvement that costs 50 percent or more of the building's value before work starts. It also covers structures with [substantial damage](https://build813.multisites.ai/glossary/substantial-damage), whatever repair is done.

A big remodel in a flood hazard area can cross the line. Then the whole house must meet current flood rules, as described under the [FEMA 50 percent rule](https://build813.multisites.ai/glossary/fema-50-percent-rule). Plan the budget with a clear value for the existing home. See [building on your lot](https://build813.multisites.ai/build-on-your-lot-tampa) for how this affects a project.

[Halo Homes can helpRenovation and remodeling](https://build813.multisites.ai/services/renovation-and-remodeling)

## Related terms

-   [Substantial damage](https://build813.multisites.ai/glossary/substantial-damage)
-   [FEMA 50 percent rule](https://build813.multisites.ai/glossary/fema-50-percent-rule)
-   [Base flood elevation](https://build813.multisites.ai/glossary/base-flood-elevation)
-   [Building permit](https://build813.multisites.ai/glossary/building-permit)

## Sources

1.  [FEMA: Substantial Improvement](https://www.fema.gov/about/glossary/substantial-improvement)
2.  [City of Tampa: Flood Information](https://www.tampa.gov/tss-stormwater/info/flood)

![Aerial view of waterfront homes on Tampa Bay with the downtown Tampa skyline in the distance](https://build813.multisites.ai/_astro/aerial-skyline.Bt8UN67d_ZwicJ3.avif)

## Start your home.

Tell Halo about your lot, your plans and your timing. A call or a short note is enough to begin.

[Start your home](https://build813.multisites.ai/contact)

Or call [(813) 956-1972](tel:+1-813-956-1972)