Tips for specifying exterior concrete surfaces

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Brooming large-area placements is a much more difficult task than brooming sidewalks or driveways. Controlling the depth of broom marks is just one of the problems faced by finishers. Photo courtesy CECO Concrete Construction

by Ward R. Malisch, PE, PhD, Bruce A. Suprenant, PE, 
and Frank Salzano, PE, PhD

Based on the information presented in the article, “Specifying Broomed Exterior Concrete Surfaces” by Ward R. Malisch, PE, PhD, Bruce A. Suprenant, PE, and Frank Salzano, PE, PhD in the April issue of The Construction Specifier, the following are recommendations for specifying exterior concrete surfaces.

Appearance (broom finish)
The broom finish should be specified to match the appearance in an existing slab or pavement of comparable size. For instance, one should not specify a sidewalk appearance for a parking structure. Also, a mockup or reference sample should be specified for appearance consistent with the placement size. The limitations of a mockup should be understood; when one is used, there should always be a repair portion so the contractor’s means and methods using the specified repair materials and procedures can be evaluated when repair is necessary.

Texture
A limited-range broom finish—such as light, medium, or heavy—should be avoided because it is hard to distinguish between textures to that degree. One should specify a broom finish as light-to-medium or medium-to-heavy. Further, texture depth should not be specified unless a procedure for measuring depth is included in the specifications.

Flatness
For parking lots and other site paving, a 13-mm (½-in.) gap under a 3-m (10-ft) straightedge can be specified. Use ACI 117-10, Standard Specifications for Tolerances for Concrete Materials and Construction, methodology for measuring with a straightedge. For parking structures, one should specify an overall floor flatness (FF) of 17 and a minimum local floor levelness (FL) of 11. (ASTM E1155, Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers, can be used for its methodology for measuring F-numbers.)

Drainage
Whenever possible, a top-surface one-way slope or a one-way top and bottom surface slope should be specified, with two-way slopes and warps avoided. A two percent slope for water drainage of suspended slabs should be specified. The structural engineer should check short-term and long-term deflections to determine their effect on drainage.

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49 comments on “Tips for specifying exterior concrete surfaces”

  1. I think it;s good to get tips, especially when you don’t really have any experience. When looking for concrete it’s good to talk with an expert, that way you get what you want for a decent price. I would do that sort of research way in advance.

  2. Thanks for sharing this advice on specifying exterior concrete surfaces. I had no idea that you had to do so many things just to have the right type of concrete on your property. In my opinion, checking drainage is probably one of the most important aspects of inspection. You need to be sure that if there is water, it won’t end up damaging other parts of the property.

  3. I agree with Dolores, it is so important to check for drainage on your pavement. If water sits on it, it is only going to last a fraction of the time that it could have otherwise. I never realized that the texture played such an important roll in this. I have always assumed that a smooth driveway was the best.

    1. Thanks, Edmond, I will definitely check for drainage so my pavement does not end up costing me more too soon. And yes, the texture is extremely important for a variety of reasons, one being traction when your car is parked during the winter if you have a sloped driveway. A lot of people do not think of it so do not feel to bad!

  4. Ward, this was an informative post about concrete surfaces. My husband and I have been thinking of installing a concrete porch in our backyard. These tips for working with concrete could come in handy. I will have to show this to my husband and see what he thinks.
    Emily Smith

  5. My father was a construction worker for many years, and I still remember helping him pour concrete in the hot sun. We used a broom to add texture to the surface. It’s been so long I can’t quite remember. What is the advantage to adding a broom finish? Is it for appearance or does it play another role?

  6. I have decided to build a new garage, and I was unsure what kind of concrete would be best for my environment. That is interesting that concrete can be distinguished by texture, I always thought that they were all the same. Thank you for the useful information, I feel more confident in making my decision!

  7. Drainage is a really important part of concrete. The water needs a path to run off so it doesn’t cause any damage to the concrete or foundation. A slight slope will help with that.

  8. I really need to get a driveway installed in front of my house. I’m so sick of having a driveway made of gravel. It’s loud and it’s really annoying. Maybe I should find someone in my area who can take care of it for me.

  9. These are some great tips, and I appreciate your advice about drainage. Having a place for water to drain is very important, because not putting this into consideration can cause problems later on. I recently moved into a new home, and the concrete on the back patio doesn’t have proper drainage, so when it rains, the water collects in a huge puddle outside the door. I’ll have someone adjust the slope, but it’s definitely better to plan this out when first putting the concrete in!

  10. I really like all of your information about different concrete surfaces. Specifically, you talk about how the appearance should match any existing slab or pavement, and I agree. Not only will this help make the end product look more uniform, but it will help your job go faster because you already know what kind of concrete you need to use, too. Thanks for sharing such great information!

  11. When dealing with concrete, it is important to know what you are doing. In the article, it lists different ways that you can specify the surfaces. Depending on what you are building, you might want to have a certain texture as opposed to another one. Either way, it would be a good idea to get the help of a professional contractor. This way, you can have the peace of mind that it will be done right and done properly.

  12. Thanks for explaining so thoroughly when and how to specify each of these concrete surfaces. I’m rather new to all of this, and articles like this help me to better understand how to communicate about it all. I’ll have to show this to my husband as well so he can learn along with me!

  13. I like how you say that the structural engineer should check short-term and long-term deflections to determine their effect on drainage. I feel like there’s such an advantage that we gain when we make a plan for the future. We have to see how what we do now affects the what will happen in the future. It takes a good drainage contractor to figure that stuff out.

  14. Hello, I am about to lay concrete in my driveway and while I liked your tips, I had a question for you. How can I find a good concrete supplier? I don’t want to be stuck with low quality concrete for my project. Any information you could give me would be a big help.

  15. That’s good to know what you can specify when it comes to these paved surfaces. Knowing what kind of drainage setup they are going to install is very important. If it doesn’t have sufficient drainage, that can cause a lot of problems. I’ll have to ask about the type of slope that they plan to put into our driveway.

  16. The first insight you give about the appearance you should have to your concrete. Specifically, you talk about how the broom finish should be specified to match the appearance in an existing slab or pavement of comparable size and how there should be a mock up made and understood. Overall, I think that doing these things will help you to know what the appearance of your surface should look like, which will ensure that it is accurate and done correctly. Thank you for sharing!

  17. I know firsthand how frustrating it can be to receive either vague or impossible instructions from a client. Since we’ll be paving a large patio next year, I loved reading your tips here on how to specify outdoor concrete work. I’ll be sure to explain what direction we want the drainage to send the runoff water and keep in mind a realistic expectation for the broom texturing. Thanks so much for helping me be a good customer for concrete contractors!

  18. This is really helpful information about concrete. I am wanting to have concrete put in for my patio this Spring. I didn’t know that there were so many specifications to consider. I will remember to ask for light to medium broom finish. Thank you for sharing.

  19. You make a great point about how flatness can be an important aspect to keep in mind for parking lots. This can help minimize water pooling and make your parking area look professional. It can be a good idea to hire a parking lot contractor to make sure that your parking lot is up to code and will be a good investment.

  20. I’m concerned about drainage for our new concrete driveway, because our home is at the bottom of a hill. Will the engineer have to design a steeper slope to compensate? Also, thanks for the information on finish. I think I’ll ask for a medium-to-heavy finish.

  21. I didn’t know there was so many little rules and things to follow with cement. I thought you just had to have it flat and level. I just hadn’t really thought about it before, but it makes sense you would want the math to be correct.

  22. The measurement of a 13 mm gap under a 3m would be somewhat similar to that of my driveway. My plan is to do paving work on it during the summer time. I guess my steps are to get some of my father’s tools for this project of mine.

  23. Thanks for sharing on texture of concrete. I would have assumed all cement was simply spread out and leveled off. Also having a slight slope to the cement makes sense so the water will drain a specific direction. Thanks for your research.

  24. I had no idea that so much decision making went into pouring concrete. I have a lot more respect for the job now. Thanks so much for sharing.

  25. One of the most important variables that need your attention is the moisture content in the concrete at the time the stain and sealer are applied. Moisture in concrete can come from two main sources. The first is the volume of water used to mix the cement into concrete.

  26. You mentioned that whenever possible, a top-surface one-way slope or a one-way top and bottom surface slope should be specified, with two-way slopes and warps avoided and a two percent slope for water drainage of suspended slabs should be specified. Do most concrete contractors know when a slope needs drainage? My brother noticed a lot of cracks in his driveway and needs to have a new one installed. Finding a reputable contractor to install it might be a good option.

  27. I found your blog to be very informative. I am greatly inspired by your posts and thinking of writing mine now. Thanks for being an inspiration to me as I was also trying to write blogs but was not getting the appropriate genre.

  28. I like the topic of this article. I never knew there were so many aspects that have to be discussed for concrete surfaces! I would hope that the contractor I am looking for would explain all of these things to me before he begins working, but if not, at least I can bring it up because I know, now. I think texture will be one of the more important topics to discuss with the contractor I hire. There are so many different options, but I’m sure some work better than others. Hopefully, they will know which ones are better than others and can tell me.

  29. I like your idea on considering texture when considering concrete. I would imagine that finding someone who has other textures would be really nice. This would allow you to find someone who is able to give you the concrete you want.

  30. We use a depth measuring gauge if needed, randomly select an area and carefully measure from original surface and press the plunger. For a driveway or small lot, we might test 3-4 areas depending on design. Good idea to specify light to medium or medium to heavy broom finishes. Making it more complicated than it needs to be can be a waste of time.

  31. My concrete around my pool is already cracking and is only 2 years old. Wish the company I had hired would have read this article before doing the work in my backyard. lol

  32. Love how detailed you get about the different types of surfacing and not only that but when each is applicable or best present in varying situations. Recently, our city installed a splash pad for the kids. They selected a smooth finish with no drainage and a slick sealant. As you can guess, it wasn’t ideal for a wet slippery surface full of running tots. They had to resurface and luckily no one was hurt before they realized their mistake.

  33. My wife and I have been looking into getting some concrete services, and I think that being able to specify what finish we want would be helpful. I like that you talked about having concrete services do a textured finish, which I think would be good looking for our patio. I’m going to have to talk to my wife once we figure out some concrete services and see what finish she wants!

  34. I know too well the perils of poorly surfacing concrete. We have seen some pretty horrific jobs in our days (we resurface pool decks all day). As you can guess, poorly selected finishing is what keeps me in business but at the end of the day, we don’t want anyone to get hurt.

  35. Thanks for letting me know that I should use a broom finish that is light-to-medium or medium-to-heavy. My current driveway is a mess; there are cracks everywhere and weeds growing up through them. I’ll have to find a good concrete contractor to help me get a new one.

  36. We’ve had various client projects related to resurfacing exterior concrete, I can appreciate the insight. Here in the desert, anything outside really gets beat up with the heat. I loved your recommendations for the finishes, especially the heavy broom. We will definitely be passing this info on to our clients.

  37. Interesting that after all this time we find the same techniques still being used. It definitely is the skill that gives the technique the magic that really makes a project look amazing. Using a heavy broom definitely is great for a finish, and to add – if you add some more weight to it you can actually accentuate the finish even further. It’s all a matter of taste at the end, but improvisation and innovation are great things!

  38. Exterior concrete surfaces is a craft not easily mastered by anybody. You must be skillfull and you show your expertise in the particular area of service. Thank you for sharing!

  39. I agree with the writer when you have a large surface it’s hard to control the depth of the broom. I do enjoy the look though.

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