# What exactly is a cassion? **URL:** \ **Category:** Factual Questions\ **Created:** [November 24, 2004, 7:52am UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439 "2004-11-24T07:52:09Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [November 24, 2004, 7:52am UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/1 "2004-11-24T07:52:09Z")
I overheard someone mention that they had to use cassions to support a home which was being built on poor soil. Typically, I have heard of either piers or pilings used for this (pier being the generic term for a vertical support and a piling being a one-piece support that is driven into place.) I have never heard anyone refer to a cassion in residential construction, and the only time that I have heard of cassions being used is in building bridges over water. I had the impression that the term referred to the formwork, typically made of driven plates, for a pier set in water, but it seems that I was wrong. So, what exactly is a cassion, and what are the defining features? ---
**Author:** ![Antonius\_Block](https://avatars.discourse-cdn.com/v4/letter/a/51bf81/32.png) [@Antonius\_Block](https://boards.straightdope.com/u/Antonius_Block)\ **Post date:** [November 24, 2004, 8:13am UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/2 "2004-11-24T08:13:08Z")
> [@cornflakes](#): > > I overheard someone mention that they had to use cassions to support a home which was being built on poor soil. Typically, I have heard of either piers or pilings used for this (pier being the generic term for a vertical support and a piling being a one-piece support that is driven into place.) I have never heard anyone refer to a cassion in residential construction, and the only time that I have heard of cassions being used is in building bridges over water. I had the impression that the term referred to the formwork, typically made of driven plates, for a pier set in water, but it seems that I was wrong. > > So, what exactly is a cassion, and what are the defining features? IANA Civil Engineer, but [here](http://www.encyclopedia.com/html/c1/caisson.asp) [are](http://en.wikipedia.org/wiki/Caisson) a couple of definitions to get you started. I’m mainly posting to let you know that you’ll get a lot further in your searches if you spell it **“caisson”**. (No snark intended, just trying to be helpful.) ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [November 24, 2004, 8:39am UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/3 "2004-11-24T08:39:02Z")
:smack: Thanks. …and essentially it is the formwork. I suspect that the home that I mentioned in the OP was built on land with a high water table. The cassions may have been needed to keep water out when pouring the foundation. (Would any mods care to fix the spelling in the title?) ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [November 24, 2004, 8:56am UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/4 "2004-11-24T08:56:39Z")
Checking a few more web pages, it seems that caisson is used in other parts of the country to describe a reinforced concrete pier going down to bedrock, or at least to bearing soil. Around here, we just call them piers. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [November 24, 2004, 2:08pm UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/5 "2004-11-24T14:08:07Z")
Interesting note… Originally, the bends, what scuba divers get was called cassions disease. When drilling deep cassions in a river for a bridge, high pressure air was pumped into the cassion to force water out. The people working in the cassions would get the bends/cassions disease from breathing the high pressure air, and not properly decompressing as they exit the cassion. ---
**Author:** ![Joe\_Mahma](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@Joe\_Mahma](https://boards.straightdope.com/u/Joe_Mahma)\ **Post date:** [November 24, 2004, 5:36pm UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/6 "2004-11-24T17:36:24Z")
> [@enipla](#): > > Interesting note… > > Originally, the bends, what scuba divers get was called cassions disease. When drilling deep cassions in a river for a bridge, high pressure air was pumped into the cassion to force water out. The people working in the cassions would get the bends/cassions disease from breathing the high pressure air, and not properly decompressing as they exit the cassion. _caisson_ ---
**Author:** ![CapnPitt](https://avatars.discourse-cdn.com/v4/letter/c/edb3f5/32.png) [@CapnPitt](https://boards.straightdope.com/u/CapnPitt)\ **Post date:** [November 24, 2004, 5:41pm UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/7 "2004-11-24T17:41:57Z")
I know you’re referring to homes, but if you pick up David McCullough’s _The Great Bridge_ you’ll learn more about caissons than you ever cared to know. And it’s readable, too! [link](http://www.amazon.com/exec/obidos/tg/detail/-/067145711X/qid=1101318688/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/104-8173026-7435913?v=glance&s=books&n=507846) ---
**Author:** ![BobT](https://avatars.discourse-cdn.com/v4/letter/b/8e8cbc/32.png) [@BobT](https://boards.straightdope.com/u/BobT)\ **Post date:** [November 24, 2004, 5:46pm UTC](https://boards.straightdope.com/t/what-exactly-is-a-cassion/276439/8 "2004-11-24T17:46:11Z")
Caissons also refer to chests that carried artillery, and later to wagons that carried this artillery as in the song “The caissons going rolling along …” > [@](#): > > Over hill, over dale > As we hit the dusty trail, > And the Caissons go rolling along. > In and out, hear them shout, > Counter march and right about, > And the Caissons go rolling along. > Then it’s hi! hi! hee! > In the field artillery, > Shout out your numbers loud and strong, > For where e’er you go, > You will always know > That the Caissons go rolling along. > That the Caissons go rolling along. > That the Caissons go rolling along.