---
title: "What Is Hairline crack? Pool Glossary | Marina Pool Services"
description: "A hairline crack is a very thin crack in the surface finish that is often cosmetic. Plain-English pool glossary from Marina Pool Services in Grapevine, TX."
url: https://marinapool.multisites.ai/glossary/hairline-crack
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Surfaces and decks

# Hairline crack

A hairline crack is a very thin crack in the surface finish that is often cosmetic.

Hairline cracks are common in plaster and decks. They often come from drying shrinkage or normal temperature swings. They are narrow, and a fingernail does not catch on them.

Watch them. If the crack grows, gets wider, shows rust stains, or the pool drops water, call a pro. A bucket test can help sort out evaporation from a leak. Cosmetic cracks can often be patched by a finish contractor. Keep photos with dates so you can compare later.

## Related terms

-   [Structural crack](https://marinapool.multisites.ai/glossary/structural-crack)
-   [Bucket test](https://marinapool.multisites.ai/glossary/bucket-test)
-   [Plaster](https://marinapool.multisites.ai/glossary/plaster)

## Need a hand with your pool?

Call or text and tell us what your pool needs. Estimates are free for qualifying services, and same-day estimates are possible when the schedule allows.

[Call (817) 896-1120](tel:+1-817-896-1120)[Get a quote](https://marinapool.multisites.ai/contact)

![A pool technician working on an equipment pad](https://marinapool.multisites.ai/_astro/technician-equipment-pad.BW5xZMNY_Zum1K5.webp)