Asking The Right Questions (About Foundations, p1)

About Foundations, p2 (Piling)

It appears that many of the contracts signed by property buyers in Dubai allow (or even require) an on-site inspection of a property before it is handed over to the buyer, thus providing the opportunity to iron out any snags. This may be all well and good as far as snags go, but what about more serious discrepencies. Might not earlier and repeated inspections serve the buyer better?

Whether multiple inspections are allowed by the developer or not, there are key questions that the buyer should seek answers to throughout the building process. In a multi-part brief, I propose to suggest some of the questions that might be asked at various stages of the building process, starting in this post with foundation issues.

General Questions

• What type of foundations are being considered?
  
• What other construction related works will proceed simultaneous to foundation work--i.e. plumbing, mechanical or electrical?
  
• What system will be used to minimize the effect of earth tremors?
  
• Approximately what percentage of the total building cost is allocated to foundation work?
  
• What will be the general time frame for each phase of construction in the foundation building process?

Although perhaps technical in nature and beyond the scope of the average buyer to clearly understand, the answers given to such questions will both educate the buyer and provide a record of builder intent and activities should questions or problems arise later.

It may in fact help to take...
A Look at What Building Foundations Are

There are according to Emporis five types of foundations, which may be used alone or in some combination in the construction of high-rise buildings:

• Pile: Consisting of vertical structural members that are forced into the ground by impact (from a machine called a "pile driver").
  
  
  
• Caisson: Similar in form to pile foundations, but are installed using a different method. Caissons (also sometimes called "piers") are created by auguring a deep hole into the ground, and then filling it with concrete. Steel reinforcement is sometimes utilized for a portion of the length of the caisson. This seems to be a method commonly used in the Dubai.
  
  
• Mat: (Also known as "raft foundations") are a foundation system in which essentially the entire building is placed on a large continuous footing. Mat foundations found some use as early as the Nineteenth Century, and have continued to be utilized to effectively resolve special soil or design conditions. In locations where the soil is weak and the bedrock is extremely deep, "floating or compensated mat foundations" are sometimes utilized.
  
  
• Spread: The structural load is literally spread out over a broad area under the building. Spread foundation systems utilize one or more horizontal mats, or pads, to anchor the building as a whole or to anchor individual columns or sections separately. Spread foundations are also known as "footing foundations" and are a type of foundation often utilized in low-rise buildings.
  
  
• Load-Bearing Wall: Buildings that have basement levels, use slurry walls at the edges to hold out the surrounding earth. In very few cases, this slurry wall or another underground wall element becomes a major load-bearing part of a highrise building's foundation.

It is important to repeat that often a combination of the above methods are employed.

Interestingly the developer of the Wind towers in the JLT development had to go through arduous negotiations with master-developer Nakheel to gain approval for raft and box foundations which it determined were most suitable for its towers. The developer spoke candidly about this issue in an online forum:

Our experts, advisors and consultants undertook numerous tests including two major soil tests to prove beyond a doubt that we would not require to undertake any piling for Wind Tower I and could instead apply raft foundation and box foundation. This system had not been used in any of the towers at JLT but has been used elsewhere including JBR. However, Nakheel has been reluctant to give the go-ahead despite our senior advisor, Dr. Colaco, himself a designer for the Burj Dubai, contesting their reluctance and giving his expert opinion on the matter. Finally, yet again, after many months delay and despite further confirmation attestation of other results, we have reached a compromise with the Master Developer which would mean that a third party, Swiss Boring, be brought in to take one final soil test, after which we expect to have the permit to start construction. Until this matter is resolved we cannot go ahead, obviously. All our clients are aware of this exhausting matter of the soil test, and I would be shocked if you have not been made aware of it and will look into it personally if you confirm that this is the first that you have heard of it SUR.

Another matter of interest is the type of work that constructing a foundation involves. This includes among other things:

• soil testing
  
• excavation
  
• shoring
  
• dewatering

It is with an eye on these processes that the observer may guage or evaluate the pace of progress on the foundation. The MAG 218 developer has indicated a schedule of up to six months. It will be interesting to learn what the plan is for when each step in the process will be started and completed and if the proposed schedule will be adhered to. Already, for apparently unavoidable reasons, there has been a delay of 2 weeks or more between the time when the foundations contractor was announced and any significant work was commenced. However, in light of the difficulties faced by the developer of the Wind Towers, such a relatively short delay might be taken with a sigh of relief.

P2 of this exposé on foundations will follow with answers to the questions posed above and include a look at methods of incorporating earthquake resistent features into foundations.

A meeting with the MAG 218 project manager to discuss these and other questions is scheduled for 31 January 2006. Any buyers interested in joining me or submitting questions to ask are welcome to do so. Contact me or post any queries below.

See About Foundations, p2 (Piling)

Go to MAG 218 Community homepage, Dubai Marina Communities or DM Blog.