Specifications provide a legal description of the work to be done and responsibilities of the applicable members on the design and contracting team.  Sounds like you are new to the field if so your firm may use a master spec and edit for projects.  As you gain more experience you will learn more what is needed to ensure that the contract documents (drawings, schedules & specs) have all the necessary information.  You can dissect a spec your firm has used before to see what items they include.  The specs will usually have any special requirements the owner requests on the project.

They come from anywhere you can cobble them!!  From a "Masterspec" within your firm, from specifications written by others and borrowed (or more likely pilfered), from manufacturer's guide specs, from military spec sources such as NAVFAC or VA, from the Construction Specifications Institute....and others.

The individual spec sections can be garnered from a variety of sources.  The difficulty is coordinating and editing those specifications into a logical, sequenced project specification that covers the technical, administrative, and legal aspects of the project.

 

There are training courses several weeks long conducted by CSI that covers just the basics. I took it a very long time ago and should take a refresher but I'll try to condense the concept of specifications for you without getting too lengthy.

The project manual, or spec book, is part of the entire building package which is refered to as the Construction Documents which also includes the drawings, contract, and eventually approved shop drawings and change orders. The Project Manual contains two main sections, the front end and the technical specifications. The front ends describe project basics such as the form of contract, use of the site, basis of award, requirement and condition of payment, etc. The technical specifications are usually divded into 15 main sections and these describe in detail the various components of the project. Each technical specification is divided into thre parts consisting of Preparation, Products, and Execution.
The Product section describes the particular building component and is
generally selected by the designer. Say in the case of concrete, this is
where you tell the bidder what strength of concrete you need for each
element and additional properties required like high early strength or air
entrainment.

There are two major philosophies of specifications. One is generally called
 performance specs and allows the contractor more leeway in how the end
 result is achieved. The other method is more of the traditional approach
where you tell the contractor the exact product or mix design that will be
accepted. Most of the information should come from the designer but
there are some lazy building professionals who cut and paste one
manufacturer's spec and try to convert it to a performance specification.
Lots of reasons not to do this, the main one being that a manufacturer will
 deliberately write a specification that only their product will satisfy.

Front ends should be job specific and generally is driven by the Client. Governent agencies usually have very detailed requirements concerning bidding, schedule, contracts and payment.

So I hope this is enough to digest for awhile

"If you are going to walk on thin ice, you might as well dance!"

Sorry about that formatting. One of the downsides to doing this on an iPhone. I thought of one more basic, that the specific material qualities come from a variety of Quasi-governmental entities such as ASTM, ACI, AAMA, Factory Mutual, Underwriters Labs or any number of industry committees.

Let's take my concrete example for instance. Concrete is cement, water, aggregate and an ad mixture or two. The properties of the main ingredients are determined by ASTM standards, except the water is generally described as 'potable'. What qualifies as potable water may vary slightly throughout north America, but not enough to make a difference. That may not be the case in remote parts of the world, so you as the Engineer must pay more attention to the specifics of the water available at the site and write your specification accordingly, like prohibiting the use of sea water in the mix.  

"If you are going to walk on thin ice, you might as well dance!"

We are in the process of reviewing our company spec's and most of them are built off of industry standards (API, ASME) and adapted to fit our business.  As mentioned above the hardest part is sorting through all of them and finding what is applicable and putting it in a logical format.  You also have to include special exceptions to account for local regulations.   

http://engineerhumor.com/

Selecting the specification and editing can be very tricky.
I've overseen a lot of rip out, and talking with bonding agents for agreement on payment for that reason. Using the same specification for NFPA 90A applicable buildings when NFPA 45 should have been used kept me busy for years. Some applications are not specified under ASHRAE, NFPA or IBC, so that can be a struggle even before you get to selecting, editing or writing a spec.

I've spent the better part of the last two weeks spec writing because there is no spec available. That is some tedious, boring business. Real fun starts this morning with meeting lawyers, contracting personnel, and safety to get approval.

After the general description of the project - I think most specs come from previous mistakes or misunderstandings....

Hi All,
These response have been very helpful. If I can narrow things down a bit more... Some of you seem to be talking about large public sector projects, which I believe would be different than specs for a small six story masonry building interior retrofit and exterior repair project (Just for the structural engineering discipline part of the work.). I was expecting that there would be one go-to spec source for small structural engineering firms to pick-up specs to use for small private projects. It seems like CSI is a bit like this?
-Testrun  

www.DraftingServices.com

CSI Specs:  http://www.csinet.org/s_csi/index.asp

AIA MasterSpec:  http://www.arcomnet.com/masterspec/index.php

 

specs must be adapted to local laws, ordinances and practices. there is no one-stop shop. Basics of your specs should be Part 1) General , Part 2) Materials and Part 3) Execution.  Note that CSI Masterformat is no longer 16 divisions, that was changed in 2004 to 50 divisions and all the division names were changed. You will have to pay for the CSI specs and then revise them as necessary. It may be more worthwhile to write your own.

Here is a free set of guide specs that could be modifed for use:

http://www.wbdg.org/ccb/DOD/UFGS/UFGS%20COMPLETE.pdf