---
title: "Step 7: Drainage Mat Installation"
url: https://stacklist.com/card/e30b8f28-c0f2-4064-8451-8ab103c671e1
stack: https://stacklist.com/c/business/stack/2d67154e-83fe-4367-99db-e7e4088ce2f9
summary: "Step 7: Drainage Mat Installation provides detailed procedures for installing a drainage mat between waterproofing membranes and topping slabs, including pre-installation checks, proper orientation (dimpled side down), and installation steps with specific requirements for overlaps, drains, and scuppers. The process includes an inspection checklist to verify correct placement and accessibility of drainage components."
tags: "drainage-mat, waterproofing, installation, roofing, membrane-protection, construction-checklist"
key_entities: "drainage mat (concept), waterproofing membrane (concept), topping slab (concept), filter fabric (concept), scupper (concept), clamping ring (concept)"
classification: "checklist"
content_hash: "sha256:6029c0eaeca5aa40bb3b41dd693013cee0932b2a206c3056904d151fce899cb3"
acp_version: "0.2"
token_counts_approximate: 536
visibility: public
agent_accessible: true
status: "final"
---

# Step 7: Drainage Mat Installation

Step 7: Drainage Mat Installation 
Overview 
The drainage mat provides a separation and drainage plane between the waterproofing membrane and
the topping slab or paver system. It protects the membrane from point loads, allows lateral drainage of
any water that gets through the topping, and maintains the flood test drainage path to the drain or
scupper. 
Pre-Installation 
[ ] Step 6 hold point is signed off. Membrane is fully cured. 
[ ] Membrane surface is clean and dry. Remove any debris before rolling out mat. 
[ ] Confirm drainage mat product matches project specification (dimple height, flow rate, filter fabric
facing). 
Orientation 
Dimpled (cup) side faces DOWN toward the membrane. The filter fabric faces up. 
Rolling the mat upside down eliminates the drainage channel entirely. Double-check before
unrolling. 
Installation Steps 
1. Unroll the drainage mat from the high point of the deck toward the drain or scupper. This helps
gravity keep the mat flat. 
2. Cut to length with a utility knife. Leave no gaps at the drain or scupper. 
3. Edge overlaps: Minimum 2 in. at side laps. Butt the filter fabric edges together and allow the dimple
patterns to nest. Do not stack dimples (too thick). 
4. At the drain: Cut the mat to the edge of the drain clamping ring. Do not overlap the clamping ring.
The drain must remain fully accessible. 
5. At scuppers: Terminate the mat at the inside face of the scupper throat. Do not push mat into the
throat opening. 
6. At walls and curbs: Turn the mat up the vertical face 1-2 in. and secure with a temporary adhesive or
mechanical fastener until the topping is placed. 
8/8/26, 12:47 AM Step 7: Drainage Mat Installation 
https://md2pdf.netlify.app 1/2 

Inspection Checklist 
[ ] Dimpled side down, fabric side up confirmed 
[ ] All side laps minimum 2 in. 
[ ] Mat runs continuously to drain without gaps 
[ ] Drain ring area clear (no mat over clamping ring) 
[ ] Scupper throat not blocked 
[ ] Mat secured at edges before topping pour 
[ ] Inspector sign-off: ______________ Date: ______________ 
8/8/26, 12:47 AM Step 7: Drainage Mat Installation 
https://md2pdf.netlify.app 2/2