Expansion Joints and Coping

bdavis466

TFP Expert
Platinum Supporter
Aug 4, 2014
5,013
San Clemente, CA
Expansion joints – or more appropriately called isolation joints – are an essential part of constructing a structurally sound pool and deck. Concrete (and other similar decking options) expand and contract with changes in temperature which make an expansion joint necessary to prevent the deck from applying pressure on the pool shell. If not for the expansion joint, pressure from the deck can cause the coping and tile to crack or dislodge. Under extreme cases the bond beam can develop cracks leading to failure of the beam and allow the entry of water and root systems from nearby landscape causing further damage.

The type of expansion joint varies based on the type/style of coping used but generally should be at least ½” thick of unobstructed compressible space for vertical joints and a “decoupling” joint for horizontal joints.

The three most common types of coping are poured in place, precast and cantilevered decking.

Poured in Place


Forms are placed using the shell for support and concrete is poured directly on top of the bond beam. The coping is usually as wide (or wider) than the bond beam (roughly 14”-16”). Control joints should be saw cut or tooled at 24” intervals but the closer the joints are, the less chance of shrinkage cracks developing. Tile is usually placed after the coping is poured to not interfere with the forms but can be installed prior if Stegmeier type forms are used.
The expansion joint is placed between the coping and deck and extend vertically the entire thickness of the deck and pool shell (if exposed).

Precast Coping


Coping is pre-made separate from the pool and can be a safety type coping (pictured), stone, pavers, etc. Tile is typically installed prior to the placement of the coping to establish a level waterline and aid in setting the coping pieces though it can just as easily be installed afterward. A mortar bed is placed on top of the bond beam to level and secure the coping in place.

In some cases, the precast coping will not be as wide as the bond beam and a notch on the backside will need to be made either during the placement of the gunite/shotcrete or saw cut after it has cured.
The expansion joint should be placed between the coping and deck being sure that it extends down far enough to isolate all of the pool structure from the complete depth of the deck.

Cantilevered Deck


The decking is also used as the coping which is placed in one continuous pour to create a seamless looking deck. Prior to pouring the deck, the level of the grade should be brought up to become level with the top of the bond beam and be very well compacted.

A “decoupling” expansion joint should extend across the entire width of the top of the bond beam to allow the deck to move independent of the pool shell. This joint can be created with a 4mm plastic sheet or 2 layers of roofing felt underlayment.

It is very important that the waterline tile is installed after the deck is placed so there is no chance of the deck expanding and popping off the tile (see tile placement in the diagram). The tile can be grouted as usual but the top joint between the deck and tile should be filled with a flexible sealant that is not silicone based.
 
Last edited:

MyAZPool

Gold Supporter
Jul 3, 2018
982
Arizona
The tile can be grouted as usual but the top joint between the deck and tile should be filled with a flexible sealant that is not silicone based.
bdavis466
Brian. Very informative post. :goodpost: Thanks much!

Can I please ask why the flexible sealant should NOT be silicone based? Just curious as to the reasoning there.
Thanks again...
r..
 
  • Like
Reactions: chemillion

bdavis466

TFP Expert
Platinum Supporter
Aug 4, 2014
5,013
San Clemente, CA
bdavis466
Brian. Very informative post. :goodpost: Thanks much!

Can I please ask why the flexible sealant should NOT be silicone based? Just curious as to the reasoning there.
Thanks again...
r..
Silicone works perfectly fine until it doesn't work anymore. Its almost impossible to remove completely and nothing really sticks to it...ask me how I know:cry:
 

Jbyslc

New member
Jun 24, 2019
3
Salt Lake City, UT
Brian,
Thank you for the valuable info! I am in the planning stages of building a pool; these are the kind of details I have struggled to figure out.
What is your coping of choice between the cantilevered and poured in place?
On the poured in place your detail doesn't show anything between the coping and bond beam, should this be isolated in anyway, or is it prefered to bond with the beam so they move together? Thanks again!
 
  • Like
Reactions: MyAZPool

bdavis466

TFP Expert
Platinum Supporter
Aug 4, 2014
5,013
San Clemente, CA
There is no need to insolate the coping from the beam since neither can harm the other.

I don't have a preference... it all depends on the look you're after but I've done far more poured in place coping than anything.
 

AUSpool

Bronze Supporter
LifeTime Supporter
TFP Guide
Sep 23, 2015
667
Brisbane, Australia.
Perfect timing. We will hopefully be pouring the pool shell in a few weeks. We have a site meeting in a couple of days and was going to raise the issue of expansion joints. PB is doing the pool shell, equipment, water tile and pebble while the house builder will be doing the boundary walls on the shell, retaining walls and deck slab, tiling and coping by tiler.

The shell will be 200mm thick while the coping tiles are 400mm wide so they will cover the shell to slab expansion joint. I’m guessing I’m looking at a cantilevered tile above both slab and shell glued down with flexible adhesive on both sides. Or ask the PB to increase the bond beam to ~400mm and go with a pre-cast situation. We may also incorporate a drain into or above the deck to shell joint. Ohh, so many decisions, hopefully the engineers can work out the detail.
 
  • Like
Reactions: chemillion

chemillion

Well-known member
May 7, 2019
72
Southern CA
Perfect timing. We will hopefully be pouring the pool shell in a few weeks. We have a site meeting in a couple of days and was going to raise the issue of expansion joints. PB is doing the pool shell, equipment, water tile and pebble while the house builder will be doing the boundary walls on the shell, retaining walls and deck slab, tiling and coping by tiler.

The shell will be 200mm thick while the coping tiles are 400mm wide so they will cover the shell to slab expansion joint. I’m guessing I’m looking at a cantilevered tile above both slab and shell glued down with flexible adhesive on both sides. Or ask the PB to increase the bond beam to ~400mm and go with a pre-cast situation. We may also incorporate a drain into or above the deck to shell joint. Ohh, so many decisions, hopefully the engineers can work out the detail.
Most of the time with the proper engineering details, it’s fine. The key is making sure the contractor follows the details and specifications.
 

chemillion

Well-known member
May 7, 2019
72
Southern CA
Expansion joints – or more appropriately called isolation joints – are an essential part of constructing a structurally sound pool and deck. Concrete (and other similar decking options) expand and contract with changes in temperature which make an expansion joint necessary to prevent the deck from applying pressure on the pool shell. If not for the expansion joint, pressure from the deck can cause the coping and tile to crack or dislodge. Under extreme cases the bond beam can develop cracks leading to failure of the beam and allow the entry of water and root systems from nearby landscape causing further damage.

The type of expansion joint varies based on the type/style of coping used but generally should be at least ½” thick of unobstructed compressible space for vertical joints and a “decoupling” joint for horizontal joints.

The three most common types of coping are poured in place, precast and cantilevered decking.

Poured in Place


Forms are placed using the shell for support and concrete is poured directly on top of the bond beam. The coping is usually as wide (or wider) than the bond beam (roughly 14”-16”). Control joints should be saw cut or tooled at 24” intervals but the closer the joints are, the less chance of shrinkage cracks developing. Tile is usually placed after the coping is poured to not interfere with the forms but can be installed prior if Stegmeier type forms are used.
The expansion joint is placed between the coping and deck and extend vertically the entire thickness of the deck and pool shell (if exposed).

Precast Coping


Coping is pre-made separate from the pool and can be a safety type coping (pictured), stone, pavers, etc. Tile is typically installed prior to the placement of the coping to establish a level waterline and aid in setting the coping pieces though it can just as easily be installed afterward. A mortar bed is placed on top of the bond beam to level and secure the coping in place.

In some cases, the precast coping will not be as wide as the bond beam and a notch on the backside will need to be made either during the placement of the gunite/shotcrete or saw cut after it has cured.
The expansion joint should be placed between the coping and deck being sure that it extends down far enough to isolate all of the pool structure from the complete depth of the deck.

Cantilevered Deck


The decking is also used as the coping which is placed in one continuous pour to create a seamless looking deck. Prior to pouring the deck, the level of the grade should be brought up to become level with the top of the bond beam and be very well compacted.

A “decoupling” expansion joint should extend across the entire width of the top of the bond beam to allow the deck to move independent of the pool shell. This joint can be created with a 4mm plastic sheet or 2 layers of roofing felt underlayment.

It is very important that the waterline tile is installed after the deck is placed so there is no chance of the deck expanding and popping off the tile (see tile placement in the diagram). The tile can be grouted as usual but the top joint between the deck and tile should be filled with a flexible sealant that is not silicone based.
Excellent Post!!
 

AUSpool

Bronze Supporter
LifeTime Supporter
TFP Guide
Sep 23, 2015
667
Brisbane, Australia.
Are expansion joints meant to be water proof? Our situation will most likely have a tile coping on the ring beam (top of the shell) and tile on a decking slab that is finished at the same height as the shell but not supported by the shell. A bit like the pre cast situation, but the decking slab is inline with the top of the shell but not supported by it. Should the expansion joint between shell and slab and tile to tile on top of each be treated as two separate expansion joints or one complete system?

The instillation of shell, slab and tile will all be done at different times. I’m worried that water egress under the tile will be an issue over time.
 

AUSpool

Bronze Supporter
LifeTime Supporter
TFP Guide
Sep 23, 2015
667
Brisbane, Australia.
I guess it will look a bit like this. Tile as coping on the shell and tile on the slab. The slab would be independent of the shell. A expansion joint between the shell and slab, and another between the coping tile and tile on the deck slab. When a deck slab is poured on a bond beam notch how do you stop it from ‘sticking’ to the notch?

78109701-15E9-4208-B241-1B12AD6C512A.jpeg
 
Last edited:

bdavis466

TFP Expert
Platinum Supporter
Aug 4, 2014
5,013
San Clemente, CA
You would be better off with a cantilever deck then so the expansion joint is between the waterline tile and the deck.

The notch is either cut lower than the thickness of the deck or add plastic/felt to separate it there.
 
  • Like
Reactions: AUSpool

rdbrad

Member
Apr 27, 2017
11
Murrieta, CA
The distance varies from zero to a half inch. The pavers are a couple of inches thick so the dirt is against the bond beam. The stone dust hardens like mortar and the pavers have a slight hump like they are starting to buckle. Should the expansion joint be completely free all the way down to the bond beam?