Sump Required in Crawlspace?

[JAE]

We have a site in Southern South Dakota where there is evidence of expansive clays. Geotechnical borings indicate a Silty Clay (CL) - light gray, slightly moist, stiff to hard, highly plastic for most of the 25' boring length. Water table was below the 25' to 35' borings.

We are designing an addition to an existing building. The existing building is founded on drilled piers, perimeter grade beam, and slab-on-grade for the interior.

We are also providing a pier foundation, but using a suspended structural floor with a crawlspace. For most crawlspace structures, I have used a small sump pit (catch basin) in the bottom of the crawlspace to enable the owner to pump out the crawlspace if needed. Our mechanical engineer is balking at the idea of placing a sump pump in an area that might freeze in winter.

The site seems to have adequate drainage away from the building - is a sump pump even necessary here? We will vent the crawlspace and also provide access to it.

 

[RDK]

Install the sump. Take the pump out in winter.



Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[jheidt2543]

Install the sump basin and the electrical outlet for the pump and light, then the Owner can put a portable pump in any time is is needed.

The vapor barrier is a very good idea, whether or not there is a mud slab in the crawl space. I would also consider ventilation of the crawl space to prevent the buildup of moisture. You can use just louvers or if you want to get fancy use a humidistat to turn a fan on and off at a specified humidity level, like >60%.