Material Takeoff Basics:  The Factor of Waste

So what is waste? When it comes to the construction realm, waste is a concept that represents “extra” material that is sent to a jobsite to make sure there is enough to complete the project.   Most commonly a waste factor gets “applied” in some form of a percentage of the originally calculated value.  For example, if you calculated that you need 100 SF of flooring, you might add on an additional 10% for waste, so your order would be for 110 SF of flooring.

So what drives the amounts of additional “waste”  that are added to the base material amounts?  Like, why in some cases you might only add 3% and in others you might see people throwing 25 or 30% additional at a project?   The reasons or “methods to the madness” can be all over the board, but usually they boil down to one of these concepts:

Expected Installation Loss

The installation process for a particular material often requires cuts, over spray,  or other expected forms of material “loss” that can’t be re-used elsewhere.  And while perhaps this might be in part to account for a few small “human error” types of mistakes,  this mainly is just part of the expected install process.  For example, to install the wood flooring, you might have to cut off 2”-3”  from many different boards in order to make them fit into the room correctly.  Those short “cutoffs” may seem small, but they can add up to a fair amount by the time the project is done.  Hence the extra amount thrown on for “waste”

Its also interesting to note that at times, the same materials being installed for the same application can generate more waste if they are installed in a different way.  Back again to our flooring example – if you installed your wood floor at 45 degree angle to the room, you likely would waste more material due to all of the angled cuts.  So in this case, instead of 8% waste, you might need 15%.

Damaged and/or Poor Quality Materials. 

We have all probably been to any type of store and observed packages of food, materials, etc that have been damaged.  Most of the contents are fine, but perhaps not all.  These things just happen.  Back to the flooring example, perhaps in a carton there is a small piece or two that is not useable due to breakage or even just a strange oddity in the wood that won’t blend nicely with the rest of the floor.   Depending on the material type, these issues may be more or less likely to happen, so estimators may adjust their waste factors accordingly.

“More of the Same” Material Used Elsewhere

This last item really relates less to the actual idea of “waste” and more to the idea of “how to estimate efficiently and quickly”.   Estimators are tasked with coming up with an accurate amount of material that will be needed to complete a project – and usually to do this in as little time as possible.  In some industries, the uses for the same material can be quite diverse and they don’t have time to count every single stick of lumber or every last nail in the project, they will often use different short-cuts and rules of thumb to get to a number, but still an accurate number, in a faster way.  At times, amongst these tricks, is the idea of inflating the amount of “waste” for a particular item so that there are sufficient amounts of that material to be used in various ways.

The plates for wall framing material are a great example.  To build the main frame of a wall, you typically need a “bottom plate” (commonly a 2×4 or 2×6) as well as two  of the same type of plates at the top.  So if you were measuring 100 LF of wall to frame, you would need 300 LF of 2×4 or 2×6 plate.  And then you might need to throw on 10% extra to account for “true waste.”  However, because some Estimators know that the framers are going to need more 2×4 or 2×6 material to add in blocking, or to use as bracing, and other misc. parts and pieces of these walls, many have found that a great way to handle providing enough material is to just send 25% or 50% more plate material in order to cover the other things.  So instead of sending 300 or 320 LF of plate material, they may actually send 400 LF of plate material.  And from experience, they know that in the end, this material won’t be left over, it will get used appropriately in the project for related applications. 

This last “reason” or method for using “waste” to increase product amounts is certainly one that you would want to eventually understand the “reasons” why you are using that method, that way it is more clear on how and why you are getting to certain values in your estimating work.

“Waste” is an absolute must to account for in your estimating work.  The key is knowing your product, your regional practices, your installers, and your project types so that you can apply the correct amount of waste.  Visiting job sites or following up after the fact to know what was left over or if additional material needed to be ordered is a great way to hone in your waste percentage factors. 

The goal with applying waste should be to have your material estimate within a very small margin of exactly the amounts that needed to be consumed.  Understand the needs, monitor the results, adjust as needed.  Repeat.

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