---
title: How to Install a Flat Roof Skylight: Step‑by‑Step Guide
siteUrl: https://logzly.com/skylightservice
author: skylightservice (Skylight Solutions)
date: 2026-08-01T20:15:58.042222
tags: [flat_roof, curb_mounted, skylight]
url: https://logzly.com/skylightservice/how-to-install-a-flat-roof-skylight-stepbystep-guide
---


Tired of a dark flat roof and dreaming of natural light? Learn exactly how to install a flat roof skylight that stays leak‑free, with clear steps you can follow today. This guide walks you through choosing the right product, building a proper curb, and sealing every joint so you enjoy sunshine without drips.

## Why a Curb‑Mounted Skylight Is Essential  

When I first tried to **install skylight on flat roof**, I grabbed a cheap DIY kit and assumed it would work. The thin metal flashing couldn’t handle the low‑slope surface, and water pooled around the opening. I soon discovered that flat roofs need a **curb** that raises the frame, directs runoff, and protects the seal. Skipping this step caused leaks that ruined drywall and wasted weekends.  

The breakthrough came after I researched curb‑mounted skylights, watched a few tutorials, and consulted a local roofer. A dedicated curb, paired with the correct flashing kit and waterproof membrane, transformed the project from a risky hack into a reliable roof upgrade.  

## Step‑by‑Step Flat Roof Skylight Installation  

**1. Pick the right skylight.** Choose a **curb‑mounted unit** labeled for flat roofs; the curb acts like a tiny balcony that lets water flow away.  

**2. Gather tools and materials.** You’ll need a circular saw with a fine‑tooth blade, drill, roofing screws, high‑quality roofing sealant, a pre‑formed curb kit, and a sheet of self‑adhesive roofing underlayment.  

**3. Mark and cut the opening.** Measure the skylight, add an extra inch all around for the curb, snap a chalk line, verify level, and cut slowly to avoid damaging the thin roof deck.  

**4. Install the underlayment.** Lay the waterproof membrane over the cut area, overlapping at least six inches onto the surrounding roof. This is the first line of defense for **how to waterproof a flat roof skylight**.  

**5. Set the curb.** Place the pre‑formed curb onto the membrane, secure it with roofing screws every six inches, and apply sealant under each screw head.  

**6. Flash the curb.** Wrap the base flashing around the curb, fold the side flanges up, and seal every seam with roofing sealant.  

**7. Position the skylight.** Lift the glass unit onto the curb, ensure it sits level, fasten with the supplied screws, and add sealant under each head.  

**8. Seal the top flashing.** Press the top flashing over the skylight’s outer edge, run a continuous bead of sealant along the perimeter, and smooth it for a neat finish.  

**9. Finish the interior.** Add a thin trim piece of wood or PVC around the opening, nail it in place, and caulk the edges for a clean look.  

**10. Test for leaks.** Hose down the roof around the skylight for a few minutes, inspect inside for drips, and touch up any trouble spots with extra sealant.  

Following these steps gives you a skylight that stays dry and lets sunshine pour in. The **curb‑mounted design** is the key— it creates the raised frame needed to channel water away and keep the installation watertight.  

## Wrap Up & Thoughts  

A little preparation and the right products prevent future headaches. Skipping the curb or using incorrect flashing will only bring leaks later, but taking the time to do it right means you’ll enjoy natural light for years without worry.  

If you found this guide helpful, consider signing up for the **[Blog Name]** newsletter for more no‑nonsense home‑fix tips. Feel free to share this post with anyone else dreaming of a skylight.  

Enjoy the extra sunshine!