Decoding Concrete Mixes: What are you really getting when you ask for 6 bag concrete?

An interesting thing happened the other day. When my field staff was pouring a new concrete foundation, they were given a competitor’s flatwork concrete delivery ticket by mistake.  The ticket has shed some light on how a contractor can meet specifications, while still short changing the customer.   In the end, the customer technically got what was likely specified, but not the long-term durability I am sure was desired.

The ticket shown does need some deciphering to those unfamiliar with concrete jargon. Under quantity it shows the number “seven”. Therefore, seven yards were delivered. The item code states “6 bag AE” and “Mid-Range 8oz”. Let’s break down the “6 bag AE” first.  This refers to the amount of bags of cement per yard in the mix design.  A straight six bag concrete mix with the correct proportion of aggregates and water should yield about 4,000 pounds per square inch for compressive strength. This is an excellent strength for most concrete slab applications. The issue, however, is that adding more cement causes more concrete shrinkage due to the higher amount paste.  This leads to more concrete cracking.  Also, more cement in the mix will also speed the setting time or as we say in the concrete world, increase the rate of hydration.  Speeding up this process will give off more heat and lead to decreased strength of the end product.  

The other component in the item code is “AE” which stands for air entrainment. The admixture adds tiny air pockets to the paste. This air is desirable in exterior concrete poured in cooler climates because it gives water a place to go if it freezes. When water freezes below the surface of the concrete it expands and can fracture the concrete.  In a basement, you do not need to add air for performance. 

If you continue reading the concrete ticket, you will see it noted that the air was doubled.  The drawback of adding air is that it interferes with the cement paste matrix (bond) and weakens the concrete.  A standard air entrainment proportion range is 4 to 6 percent of the cement paste per the American Concrete Institute (ACI). Higher amounts significantly reduce the strength of the concrete. A double air dosage can reduce the strength by as much as 600 psi.

The next item code or ingredient shown on the ticket is mid-range water reducer.

This is added to the concrete to increase the workability of the concrete without adding water to the mix.  (Adding water will directly decrease the concrete’s strength.)  The admixture will, however, accelerate the speed at which the concrete sets.

You can also see two hand written notes on the delivery ticket. One is “1%CC” and the other is “1% HE”. Both of these are accelerating admixtures to reduce labor time during the finishing process.  These will increase the heat of hydration and may then also increase the chance of shrinking before the concrete is strong enough to resist the tensile and flexural forces this will create. If the air temperature is cold, this combination works. If the air temperature is higher than fifty degrees, the risks of adding these admixtures start to outweigh the benefits.

           

So, now you should have a good understanding of what was in this concrete, which brings me the question of why was the mix designed this way? 

To answer this, I now must bring up the challenges associated with pouring concrete directly on a vapor barriers Vapor barriers are necessary to keep water vapor and other gases, such as radon, below the concrete.  When you pour on the vapor barrier, the bleed water (water that is not needed for the bonding chemical reaction in the cement paste) can only go up and out the surface. This is a problem for many reasons.

The biggest problem is the additional cost of labor. You cannot begin the finishing process until the bleed water is gone.  The vapor barrier causes more bleed water and we must wait longer before we can start finishing the surface.

As slabs harden, they will curl towards the air side of the slab.  More bleed water means an increased chance of curling which ultimately can cause an uneven floor surface.  Both of these issues can be controlled through good concrete practices.

My assessment of the situation is that rather than use good concrete practices to control bleed water, this contractor chose to add extra accelerants to the mix and double the air content to alleviate the problems I just mentioned.  The heightened air content will result in a slab with many voids for the bleed water to hide in as it is making its way to the surface.  Therefore, more times than not the finishing process will begin before the bleed water is all out.  Trapped bleed water will cause numerous durability issues as time goes by. In fact, I think it is probably the number one cause of concrete slab call back issues. 

The accelerants added speed up the setting process and decrease the labor time on the job, but will lower the strength curve over time.  The concrete will gain strength quickly, but if used when air temperatures are above 60 degrees, the ultimate strength of the concrete will really suffer.

Therefore, even though the concrete contractor ordered and installed a six bag mix (4,000 psi), the owner received a product that has a slim chance of performing like a six bag mix should. The corners cut gave the contractor labor savings and gave his customer a potentially defective concrete floor.

This brings me to the point of this entry.  We specify our standard slabs to be a minimum 3000 psi concrete mix and know that when tested, the 28 day strength exceeds this specified number.  I am absolutely sure that we are putting out a much better product using our concrete mix than this competitor who may state they are using a higher strength concrete.  Unfortunately, just specifying the strength of concrete does not give you more as the customer.  You need to choose a contractor with the knowledge to properly install the concrete AND the moral integrity to not take short cuts that reduce the structural integrity of your concrete.

The Green Foundation Contradiction

In our area, there are several contractors considered to be the “green building” leaders. They market themselves as the innovators of the green building movement, but actions do speak louder than words.

After recently seeing several ads in a local publication, I decided to do some online research of the companies touting their green building expertise, especially as it relates to foundation construction. One builder I researched includes an asphalt waterproofing membrane on all jobs. Another indicated that a Platon sheet membrane was their choice of basement waterproofing.

Anyone versed in green building should know that Platon is a better choice when wanting to build “green” because it is manufactured with a high level of recycled content. My impression was the company offering the Platon probably does have the better grasp on how to build in an environmentally friendly manner.

At the same time, I thought to myself, wouldn’t it make the most sense to build a foundation correctly so that waterproofing isn’t a necessity? That’s what makes sense to me and that’s our goal at Coello and Associates.

As far as I know, the same builder using the asphalt-based waterproofing on all projects also chooses to use a foundation contractor that is known for its low cost, not its high quality. This contractor substitutes industry’s best practices with waterproofing as a band-aid to keep the basement dry. These foundations lack the needed steel reinforcement, control joints, and proper consolidation techniques required, so a waterproofing membrane is added to protect the contractors when the walls crack.

Adding an asphalt based waterproofing membrane is not an environmentally friendly practice. To market that sustainability and “building green” are your main objectives, but to make this a standard inclusion, seems wrong on many levels. There are some things in building that are absolutely necessary, but may not be “green”. Waterproofing is not one of these things.

For the sake of full disclosure, I do admit that our company does make waterproofing available to those who want to add it, but this is not a standard inclusion. We see the waterproofing as an insurance policy owners can buy to extend the warranty on their foundation. On a bit of a side note, the product we offer does have a transferable warranty that will cover the repair of the leak. This is a good thing. Not all waterproofing warranties work this way. Others warranty only the product itself, so if a leak occurs, more of the same material would just be applied to the problem area. The term “dry basement guarantee” tends to be thrown around a little too loosely if you ask me.

There’s no denying that having a dry basement is important, but that’s not the only thing to consider. The foundation must support the loads applied to it. In order to do this, the industry’s best practices must be followed and reinforcement in the foundation is a must. The most “green” quality of a concrete foundation is how long-lasting it will be if poured correctly and in a manner that works with the conditions of the building site. Unfortunately, this is often ignored in favor of a focus on the short-term, meaning adding waterproofing to cover up foundation construction flaws.

Homeowners must really do their research when choosing a builder. Some builders are great at marketing themselves, but don’t necessarily build a great house. Just because the builder touts their green principles and can meet LEED guidelines, it does not mean they are following through on the true promise to be green.

Control Joints in Foundation Walls

Perspective is a very interesting concept. Depending on how you perceive something will drastically affect your logical thought processes. What does any of this have to do with concrete? Well, when it comes to the importance of control joints, it relates very well.

Industry professionals and lay people alike seem to get thrown on the importance of control joints in vertical concrete. Almost all parties agree that concrete slabs need joints to help control where the concrete will crack on flat slabs. However, those same people will not relate to the importance of control joints when the concrete is standing up. Their perspective due to the concretes orientation is different.

Whether concrete is vertical or horizontal it shrinks and cracks during the hydration process. Just because it is vertical does not mean the concrete is under some other mysterious force of nature that prevents it from cracking. A foundation crack is more serious due to the fact that now a place for water to get from the outside is present. Therefore, the installation and drainage details are vital to the performance of the concrete foundation wall.

I have encountered two examples of people realizing the importance but not willing to actually follow through with the details. One example was in a discussion with a vendor a few months back. The vendor was a national corporation selling asphaltic based waterproofing membranes. He called to explain the benefits of his product over our current Tremco Barrier Solutions Tuff N Dri product.

His first sales pitch was delivered in a question. He asked how many foundations we did, how many were waterproofed and what percentage had water intrusion call backs. When I gave him the answer of about five to ten percent were waterproofed and less than one percent had a call back I heard total silence. He then began to query me on how our company could have such great success compared to all other areas of North America. I explained to him about our “Integra” foundation system with the steel reinforcing, concrete mix design, consolidating techniques, and the control joints with the water stop system. Once complete with the explanation he stated that there was no need for him to call us anymore. His waterproofing membrane could not add any more value because we had developed a fool proof effective system. The key, he said, was the control joints and water stop and most people’s perspective is to add the waterproofing band aid and transfer the risk of failure to someone else instead of doing it correctly.

The second example came during a site inspection of one of our foundations. We had just completed a foundation in a newer subdivision and a competitor did a foundation next door. I went over and checked it out. The foundation had just been completed a day earlier and the job was ready for backfill. The thing that jumped out at me was that there were no control joints in the foundation walls. I knew the competitor and that practice was fairly common. A few weeks later when I was in the same subdivision again I stopped back at the freshly backfilled site. Someone must have requested control joints to be cut into the foundation.

Now control joints are good when done per industry standards. However, these were not. What they amounted to was a faux control joint. The joints were only on one side of the foundation, were a total of less than three eighths of an inch deep on a nine and five eighths inch thick wall, and no water stop or waterproofing was done. Standards call for foundation wall control joints to be either formed in or cut in within forty eight hours of the pour, the joint needs to be as deep as twenty five percent of the total thickness of the concrete, should be on both sides of the wall if possible, and some type of water stop or waterproofing should be done so the foundation does not leak when the joint cracks. Now in the eyes of the owner he got a control joint. How effective it will be will be determined over time.

No matter what your perspective, the only way to do concrete right is to put in control joints. If the control joints are in a concrete wall, please make sure they are not an illusion but actually are a functioning part of the overall foundation system.

We've Found The Bottom

Each day new reports continue to surface sighting data that suggests the real estate market is beginning to rebound. I, like many others in the industry, try to read the signals to gain a better understanding of where the market is headed. Once the winds of change reveal themselves, the industry can chart a course for recovery.

One of the most critical things to watch is the state of existing home sales. In our area, we continue to see progress. It may be slow, but at least it is occurring. The inventory is decreasing and the average time homes are spending “on the market” has also gone down. These macroeconomic signs are beginning to breathe life into what was a market on life support.
Whether it is the low interest rates, affordability index, or outright great deals on real estate, people are beginning to feel comfortable with the current value. As the market begins to climb the mountain of recovery, there will now be new challenges and pitfalls to face.

More and more contractors and builders are on the brink of insolvency. The increase in work may actually be a curse instead of a blessing. When new home construction picks up, so does the need for working capital to fulfill the labor and material liabilities. In the process this uses up the cash on hand. Due to the rapid change in risk evaluation from lenders, it is almost impossible to get financing once the cash is used. In many cases this is putting the final nail in the coffin.
It will be prudent for anyone purchasing a product or service currently to seriously consider the long term health of the organizations they will be purchasing from. If the builder or contractor cannot finish the project or is not around to service the warranty, it will not do much good for the consumer. Many of these construction companies are privately held and currently show no signs of financial distress making it very hard for the consumer to be aware of any potential problems. My suggestion is to ask other people in the industry and also trade organizations they belong to in order to acquire good background knowledge on the company’s health.

The signs point to the beginning of a long and slow recovery, but this may just bring an end to many of the companies that have struggled thus far to stay alive. It is an era of great opportunity but also of increased risk for those who do not do some homework. I know our organization is optimistic about the future and will begin to navigate forward with a road map clearly marked to avoid these obstacles.

Lessons Learned from the Decline in New Home Construction

Consumer’s motivation to buy is not always done with long term value in mind. The buying patterns of the consumer have been developed over time to not consider long term repercussions of a bad purchase. We have learned through purchasing more and more consumables (i.e. food, paper products, clothes, cell phones, etc…) that if a product does not perform to our expectations, we just choose a different brand next time. Our lifestyles have become more hectic and products of convenience are more available thus developing a consumer that is very seldom punished for poor decisions. A hard lesson is now being learned by many owners of newly constructed homes that large purchases need to be done with a different strategy.
If you buy paper products that do not perform, there is not much risk because the product was not that expensive to purchase. We make low-risk purchases on a daily basis, so our skills are not honed in on choosing more sophisticated products. When it comes time to make a much more sophisticated purchase like a car or home, some consumers apply the same principles as they would for simple buying decisions. They may not base their decisions on craftsmanship, history, reputation, quality, or experience and instead focus on getting a great deal. Oftentimes these great deals are too good to be true.
During the rapid growth of the new home market which occurred in the first half of this decade, I observed two disturbing trends. Buyers seemed to put aside rational buying practices and chose newly established construction companies or very large national builders to build their home. Choosing a new builder over an established one just doesn’t make sense to me in most situations.
I witnessed many new builders spring up during this period that were great marketers, but had little experience building homes or running a construction business. Not all of these builders failed; some chose good subcontractors to help them along the way and others were saved by patient homeowners. In the end, most of the builders that repeatedly sacrificed quality have all but vanished. This has left behind many disappointed homeowners with no support.
I hate to make a blanket statement that choosing a national builder was a bad idea, but it’s more that I would not have made that choice. These companies were in fact run by very seasoned business people. It’s not so much a matter that they didn’t know what they were doing, it was more of a matter of priorities. Along with high demand came a large potential for profit, so the bottom line often took precedence over fulfilling customer’s needs.
What’s worse, the marketing used by many national builders, as well as some of the local builders in our area, seemed to prey on the illogical consumer. The ad programs created a “buy now” mentality that clouded the judgment of many people. Perceptions that if one housing development sold out, the next would be much more expensive caused knee-jerk reactions. Waiting lists and lotteries were even held in some of the overheated markets. At face value, it may have been an accurate assessment to believe prices would rise if they waited. However, when the cloud of overzealous buying ended, the consumer has found that the value they received was much different.
What most consumers did not do was their homework. Like any big organization, national builders have set procedures across the country to keep control. In most cases, each division is not allowed to act independently. Therefore, they were not adjusting their specifications or using subjective reasoning when determining the products or craftsmanship that would be best in each different region. Mandates were given, such as getting three bids on each discipline, with the lowest bid usually being the basis for their decisions. If the contractor missed something or bid it incorrectly, it was the homeowner and trade partner that suffered and not the builder.
National builders tend to rely on their specifications and give no credence to whether the contractor or vendor can or will deliver on the specification. What made this even worse was that in a booming market, production moved quickly with missed specifications often going unrecognized. Due to a lack of knowledge and often access to the site, many customers moved into their homes without even realizing they didn’t really get what they had paid for. Project specifications do not normally affect the structural integrity of the home, but can still greatly influence the joy, livability, and value over time.
Now that the building industry has slowed down, I really hope some lessons have been learned. For the builder, I hope they all take this time as one to focus on rebuilding their companies to be ones that create high-quality homes that fulfill the needs of their customers. Even homes being built on a budget need to be built with solid building principles in mind. As for the consumer, I think we must also learn from this lesson. We must understand the consequences of making high-risk purchases on a whim. Our due diligence is importance not only to protect ourselves, but because that is what holds builders accountable.
As the new home market begins to work through and regain steam, I hope a league of builders will surface that not only have the required knowledge and experience, but also honesty and integrity.

Want to build a home? The time really is now!

Everyone loves a great deal. From finding a highly sought after item on sale to receiving better service without paying more, American consumers appreciate the value in getting more for less. Anyone buying a new home right now is getting a great value. Most material costs have risen dramatically over the last twelve months, yet the cost of a new home has either fallen or remained steady in most markets.

Commodity prices, shipping costs, energy costs, insurance premiums, and other cost drivers have risen in double digit fashion. In order to survive in the current market, efficiency has become the path to survival. New technologies must be embraced and properly executed. In many cases, this will improve the overall quality of the projects.

Specifications and building timelines have tightened dramatically as expectations for what is produced has climbed. The buildings being constructed today are more energy efficient, safer, and require less maintenance than any time in our country’s history. Yet, the cost of a newly constructed home is at its lowest level in half a decade.

Due to the prolonged new home market correction, a cleansing has occurred in the market place. The better builders, subcontractors, and tradespeople have survived. Therefore, now more than ever you have the best chance of having the best craftspeople working on your new home project. The project should go more smoothly at this time and should be constructed well above industry standards if a reputable builder is chosen for the job.

If the time works for you financially and logistically, there really isn’t a downside to building now. Waiting to build; now that’s where I see the risk. There are quite a few people out there planning to build once their homes sell. As the market turns, these homes will inevitably sell, and the demand for building new is going to rise at a rapid rate. As the demand grows, the pricing should finally grow to account for the increased costs that have been building over the last couple years.

The level of quality will also not be where it is now. As I mentioned, the best of the best in the trades are working right now. As demand grows, the less experienced and lower quality tradespeople will be added back into the mix.

In terms of value, it really is a great time to build a home!

What I Learned on my Spring Vacation...

I am just trying to decompress from my trip home from Austin, Texas. I was away on Easter break with my three sons and wife. Like most passionate construction professionals, I am always intrigued to see how our building practices in Southeastern Wisconsin compare to other areas of the country.

We were fortunate to stay in a nice development built by a leading national builder. It is about two to three years old in what is known as Texas Hill Country, just on the shores of Lake Travis. The mixed use community consisted of multi-unit condos, cottages, and million dollar estates. Overall, my first impression was positive as we drove through the luxurious complex. It was obvious that the designs were put together by excellent planners and architects. Everything from flow patterns and colors to the natural landscaping all worked together to create a true Texas feel.

The developers obviously had great expectations with planned kayak marinas, a camping area, numerous walking and hiking trails, and other amenities. Most were started, but it appears that as sales slowed, so did the capital expenditures needed to complete these projects. Most will not suffer from neglect, but it brought into question when they will ever get completed per the original lofty plans. I also caught glimpses of this in the construction of the condo type units.

I viewed a number of buildings in various forms of construction. It was not that the structural integrity of the buildings was compromised, but more the fit and finish. For instance, the decks were built of high-end composite decking. However, the floor joists were not level and a hump lifted the deck by 3/8 of an inch or more. This difference was just short of creating a tripping hazard. The pre-manufactured box cabinets in our master bath had poorly done miters which left gaps at the base. The poorly executed caulking left infiltration points for ants and other insects in many areas. So while my breath was taken away by the woodwork, granite, and furnishings, the longer I stayed, the more it felt like something was lacking.

As the current downturn in the housing economy persists, I hope the consumer educates themselves and learns about the difference between just doing the job to the minimum versus really following through on the details. Even with licensed contractor requirements or required inspections, it will still always be the general contractor’s responsibility to insist on perfection.

I truly believe that the contractors with a dedication to building a flawless product will be the ones that endure through the current dip in our economy.

I have heard that many contractors in our area have been choosing to switch subcontractors in an effort to save money. We all know you most always get what you pay for and this has had an effect on the overall quality of the homes being built. In order to build a home that will yield homeowner satisfaction for years to come, contractors cannot compromise quality through the building process. Following these principles will also help to ensure that the value of the homes appreciate over time.