Pile Foundations??

If you have a basement - which this building sounds like it may have - then a raft foundation may be a solution.

Of course, a soil report first with foundation recommendations is first on your list of things to do.

If this is really just in the first stages of development - as in feasibility - you can use the local geological maps and the local building control officers to get an indication of the bearing strata and possible solutions. Again, it is best to get a geotechnical specialist's advice for which he will generally give a short report and an estimation as to the likely cost of a thorough soil investigation.

Hi owenrog,

The design selection should be be based entirely upon the soil investigation work as this will determine the actual bearing capacity of the stratum beneath the intended structure.

Clearly you will want to expend as little as possible upon this element of the works and therefore the simplest solution is usually the most attractive one.

As has been already mentioned the raft foundation has much to commend it as it distributes the weight over the maximum area. A problem arises when the geological conditions vary dramatically in the length of the slab therefore rendering liable to failure by bending. Notwithstanding this you should consider the foundation very much an integral part of the building's functionality as a lightweght superstructure may well avoid the necessity for a complicated and therefore expensive ground work.

Good luck,

Massey.

Our site (old DuPont site) used large square footers under each column to "float" on the soil. Need to know the load bearing capacity of the soil and column load. This was not sufficient for a heavy industrial use, but may be OK for commercial.

Dear Owenrog,

After reading your posted question I assume that you do not have much design and analysis experience to date with soil mechanics and foundation design, including pile foundations.

Before you go much further, may I suggest that you obtain a copy of a excellent engineering textbook "Foundation Design and Analysis", authored by Joesph E. Bowles, PE. I believe that this text is no longer being printed, but you may be able to obtain a good used copy either at your local public library or purchase one relatively cheaply from Amazon.com. IMHO, this is THE "Bible" of foundation design and a must read and STUDY when it comes to the interaction between any foundation type and soil mechanics.

If you are not an experienced structural or geotechnical engineer then IMHO you have no business designing a building foundation let alone the building itself. Please leave that to the design professionals, especially in selecting the proper foundation.

Have a great sunny day!

Hi Captn,

Don't forget 'Soil Mechanics in Engineering Practice' by Karl Terzaghi and Ralph Peck as a Bible on foundation design. my copy dated 13/10/66 has been a good standby down the years and anything I've built by their standards have stood the test of time.

Keep up the good work.

Massey.

Hi Massey,

You're absolutely correct! I should have included "Soil Mechanics in Engineering Practice" by Terzaghi & Peck in my posting. I thought about it while writing my post and got side-tracked by a Godzillion telephone calls, hence missed writing about that beautiful text! I am totally in remiss for not including the true Godfather of soil mechanics, and therefore I deserve 10 lashes with a wet noodle on my bare arse!!! *LOL*

I too have used Terzaghi's text on many a civil works project in the past, and they too have held up under the test of time as well! My text is as ancient as your copy and a bit tattered and dogeared too, but I'll never let anyone borrow it for fear that it never gets returned (like other textbook lent in the past to Jr. Engineers and the like). It's too bad it isn't in print any longer....the older editions were the best!

Please keep up the great work as well Massey! Please have a great sunny day!

Hello "owenrog",

You express a curiosity regarding the load bearing capacity of [low load bearing soil]

But you do not explain just why said soil has this is rated as [ low load bearing ]. I have seen buildings constructed over former construction and demolition landfills that only required "GRID WORK FOOTING" POURED AT THE SAME TIME AS A MONOLITHIC CONCRETE SLAB Floor". The sizes and placement of these thickened/reinforced areas beneath a floor that was likewise thick enough to handle the anticipated future loads must be designed by a Structural Engineer who specializes in this method of construction.

I have also seen this kind of foundation designed for use over soils that have a high water table beneath the surface, generally sandy soils that can carry moderate loads of buildings relatively light weight in construction, such as steel framed with light weight preformed exterior panels and a minimal number of interior walls and to be used for storing of materials that are bulky but not heavy.

The possible need for the use of various pilings will depend upon possible loads that will be placed on the foundation and maybe the possibility of shifting.

I have found that the use of screw pilings can be a less expensive method of supporting constructed loads than driven pilings. It all depends upon just how deep one must go to reach soils suitable for carrying the load to be placed on it. These types of pilings are placed using a hydraulic power head that screws the piling into the soil. Little or no digging is required. Additional sections can be added as is needed as and necessary to achieve the load bearing capacity required. However soil borings and an assessment of the specific location of each anticipated screw pile is advised to reduce the cost of possibly driving piles to a greater depth than is necessary for each individual location.

TMF