AUST Ahsanullah University of Science & Technology Department of Civil Engineering Course Name: Geotechnical Engg. Lab. II Course No.: CE 442
Assignment On: Floating Foundation
Submitted By, Group-05 ID: (09.02.03.046-047,049,050,051, 053,056,057,058) Year: 4.1/A
Student ID
Name
09.02.03.046
Yeasin Talukder
09.02.03.047
Firoz Mahmood Ovi
09.02.03.049
Shaibal Ahmed
09.02.03.050
Iftekhar Hussain
09.02.03.051
Rafsan Jany
09.02.03.053
Rezwana Binte Hafiz
09.02.03.056
Azam Ahmed Oli
09.02.03.057
Hamidul Ahasan
09.02.03.058
Tariq Md. Shamim
Signature
•
Definition of Floating Foundation
A soil-supported raft or mat foundation with low bearing pressures. (globalsecurity.org) A floating foundation is a foundation that does not use footings. The floating foundation is a poured cement slab that has two deep edges going just below the frost line in northern climates. The floating foundation actually does float on the earth and moves as temperatures compact and expand the soil. The floating foundation is very common in garage floors and mobile home slabs. In many parts of the world, the floating foundation is simply referred to as a slab foundation. (wisegeek.com) Where the soil strength is poor, and there is uncertainty about how successful a conventional foundation
and footing system will be, one alternative is to use a floating foundation. This could be a raft or a mat foundation. The characteristics of both include a reinforced concrete foundation which forms a continuous pad under the entire building. (Essentials of Home Inspection, 2003) •
How it Works
Figure: Floating Foundation
A raft foundation has side walls (forming a basement or crawl space) of concrete, with steel reinforcing integral to the pad, forming a raft or boat. The goal in this type of construction is to end up with the soil below the building carrying the same weight as it did before the building was there. This is done by excavating the amount of soil that weighs roughly the same as the finished building A mat foundation is a thick floor slab which extends under the full area of the building. It is slightly thicker at the edges (and sometimes at intermediate points), and it floats on top of the soil distributing the building weight evenly over a large area.
Figure: Cross sectional view of a floating foundation
Once a building is up, not much can be seen of floating foundation details. Like other footing and foundation systems, time is the best measurement device, and evidence of building shifting or settlement
are the only clues for the home inspector. These special foundations usually have special design work done by engineers. It is desirable to know who designed and built the structure in case of questions or problems in the future. (Essentials of Home Inspection, 2003) •
Problems & Solutions
In a typical floating foundation, the plumbing and electrical lines are fastened to the slab by simply running them through the floor as it is poured. This means that the plumbing, drainage and electrical lines must all be completed prior to pouring the slab or foundation. This type of design can lead to very expensive repair bills if the plumbing requires work in the future. In many cases, it is a much more affordable method of building than using a footing equipped foundation.
In warmer climates, the floating slab is much friendlier to homeowners as it does not flex as much without the extreme changes in temperature. The floating foundation also aids in cooling the structure, as the foundation's contact with the ground draws cool temperatures through the concrete and disperses them throughout the building. When constructing out-buildings such as sheds, the floating foundation can take on another meaning. Some flooring systems for outside sheds are known as floating foundation floors and do not require any concrete to be poured. In these applications, the foundation is merely lumber framing placed upon blocks. This allows the floor of the shed to sit elevated off of the ground. This design prevents harmful water from seeping into the shed and protects the shed's contents
from becoming damaged by water or moisture. When pouring a floating slab foundation, it is imperative to install reinforced steel rods or heavy wire mesh in the floor prior to pouring the concrete. The wire and steel prevent the floor from cracking and breaking as the slab flexes with the earth. Without this reinforcement, the slab will likely crack and possibly cause damage to the walls and ceiling, as the floor will be allowed to flex unevenly. Often the flexing of an un-reinforced slab can cause doors to improperly close and open and windows to stick or even crack. Walls are also subject to cracking, and drywall is prone to break at the seams. (wisegeek.com)
Bibliography (n.d.). Retrieved from globalsecurity.org. (n.d.). Retrieved from wisegeek.com. (2003). In Essentials of Home Inspection. Dearborn Publishing.
