---
title: "Section 4: Railing Embed Waterproofing"
url: https://stacklist.com/card/d6a6a4de-29aa-49ce-82f1-47ab0e0cc410
stack: https://stacklist.com/c/technology/stack/ccc8a635-1426-4960-958d-568d07671c5e
summary: "Railing embed waterproofing failures typically result from treating post penetrations as structural rather than waterproofing scope items, causing caulk failure within 5-7 years. The TTP-6 pocket method prevents this by wrapping the membrane into a formed concrete pocket before the railing post is set, requiring proper coordination between structural and waterproofing contractors."
tags: "waterproofing, railing-penetration, balcony-construction, membrane-installation, scope-coordination, ttp-6-detail, construction-specification"
key_entities: "TTP-6 Pocket Method (technology), S60 membrane (technology), scope coordination failure (concept), balcony waterproofing (concept), railing post penetration (concept), flood test (concept)"
classification: "reference"
content_hash: "sha256:a6ecd1dc7e04aa2357d4680a824603600ce7b4e02403293c9d564ad7b6597030"
acp_version: "0.2"
token_counts_approximate: 578
visibility: public
agent_accessible: true
status: "final"
---

# Section 4: Railing Embed Waterproofing

Section 4: Railing Embed Waterproofing 
The railing penetration is the most common failure point in balcony waterproofing. Here is how to
spec it correctly. 
Why Railings Fail 
Railing failures happen when the post penetration is treated as a structural scope item rather than a
waterproofing scope item. The result: 
Structural sub sets posts through the membrane after waterproofing is complete 
Penetration is caulked but not integrated into the waterproofing system 
Caulk fails within 5-7 years 
Water tracks down the post, through the penetration, and into the framing 
This failure is not a material failure. It is a scope coordination failure that starts in the spec. 
The TTP-6 Pocket Method 
FM's TTP-6 detail uses a formed pocket in the concrete topping to receive the railing post. The
membrane wraps into the pocket before the post is set. The post sits inside the waterproofed pocket, not
through the membrane. 
Sequence: 
1. Waterproofing applicator installs S60 membrane across full deck including pocket forms 
2. Pocket form is removed after membrane cure 
3. Membrane wraps the interior of the pocket per TTP-6 
4. Flood test includes all pocket conditions 
5. Topping is placed with pockets formed in 
6. Structural sub sets railing posts into the pre-waterproofed pockets 
7. Post-set grout or sealant is applied by waterproofing applicator, not structural sub 
Division 05 Cross-Reference 
8/8/26, 1:10 AM Section 4: Railing Embed Waterproofing 
https://md2pdf.netlify.app 1/2 

Add this note to the structural (Division 05) railing spec: 
Railing post pockets are waterproofed under Division 07 per FM TTP-6. Structural installer shall
not penetrate, cut, or modify the waterproofing membrane at any railing location. Coordinate
railing post setting sequence with waterproofing applicator. 
Pre-Installation Coordination Language 
Add to Division 07 Part 1: 
1.4 COORDINATION
A. Coordinate railing post pocket locations with Division 05 contractor 
before membrane installation.
B. Railing post pockets shall be waterproofed per FM TTP -6 by the 
waterproofing applicator.
C. No post - set penetrations through the membrane are permitted.
D. Include all pocket conditions in the 24 -hour flood test. 
8/8/26, 1:10 AM Section 4: Railing Embed Waterproofing 
https://md2pdf.netlify.app 2/2