Recently, we had a concrete slab installed in the yard. Our installation came out very well, but there were a few “hiccups” along the way, which could have been avoided with a little foresight.
The concrete pad we had installed – February 2017.
There’s quite a few items that are worth considering for folks that are planning on installing a concrete slab in the new future. Before soliciting a contractor, it’s best to get an anticipated budget. Figuring out a rough budget will require a tape measure, temporary markers, and basic math/geometry skills. A temporary marker can be a screwdriver inserted into the soil or a brick. Use the temporary markers to lay out the area you would like to install a new slab. For computation purposes, you’ll want to have enough bricks to lay out basic geometric areas, i.e. square, triangle, etc. Once the area is laid out, find the total square foot (sqft) area of the proposed layout.
For a basic 4″ thick slab, you’ll want to multiple the total area by $5 per sqft to obtain a very rough approximate of what a contractor may quote you. There area many variables that could inflate this cost: the job is too small to offset contractor costs, additional work required to build up the foundation, location of site isn’t easily accessible, different job markets, etc. The idea of running preliminary numbers is to give the homeowner a ballpark idea of the level of effort that will be required.
Although some of the following topics may be assumed, it is worth having a conversation with the contractor concerning your expectations. The following discussion points should be covered so that you both have an understanding of what is being provided and what is deemed as acceptable.
Qualifications: I’m assuming that you will solicit contractors based on references, business license, etc. Every job is unique, but it does help to have an understanding of the contractor’s capabilities. The contractor should be able to identify other projects that you may be able to review.
Concrete depth: 4″ is the typical depth for light foot traffic (sidewalks). In the event that you’re looking for something more than light foot traffic, you may want to consider going thicker. You should anticipate a higher cost for thicker slab requirements.
Rebar and metal mesh: If you’re pouring concrete next to an existing concrete foundation, you’ll want the contractor to drill into the existing slab and connect the two slabs via rebar. In the event that the land starts to shift, the slabs are less likely to pull apart from each other. The metal mesh inside the concrete serves the same purpose, but only to assist in sections of the new slab peeling away from other
Expansion Joints: Expansion joints are installed in concrete to control cracking. If you’re walking down a public walkway, you should notice horizontal grooves that are perpendicular to the flow of foot traffic. These “grooves” are considered the concrete expansion joints. Concrete expansion joints are areas where the slab has been intentionally weakened (groove) or intentionally broken (wood form separation) where cracks in the concrete are intended to run along these lines.
Top finish: Concrete can have finished surfaces that vary greatly from very smooth to very rough. The issue with smooth finished concrete is that pedestrians are susceptible to slipping on the wet surface. By asking for a brushed finish, the top layer will have better traction. Some concrete contractors can be very creative in the type of finish. Please feel free to inquire about the different finishes a contractor can install (there may be extra labor associated).
Side finish: Commercial concrete installation typically involves utilizing a cement vibe to help minimize the internal “honeycomb” effect. During the pour, the contractor can help minimize the effect of the honeycomb showing on the external walls by tapping the forms with a hammer. Another option is for the contractor to refinish the edges by dressing up the sides with mortar. From a work perspective, I would rather tap the side. This topic should be approached if there is any issues accepting an installation with visible honeycomb on the side of the new slab.
Top and Side edges: Concrete is not a material that should be left with sharp edges. Over time sharp edges are points where the material will break off. By asking the contractor to “round all edges”, you’re giving them the direction that there shouldn’t be any “hard 90 degree edges.” There are forming tools to round off an edge. One potential option is a chamfered edge. The chamfered isn’t as popular in residential applications as commercial applications. The chamfered edge consists of a flat plan 45 degrees relative to the two walls of the slab.
Concrete corners: Corners of a slab can be an angle (hopefully with a rounded off edge) or a rounded corner. The rounded corner is typically specified in inches. The best way to explain a rounded corner is to draw two different sized circles. Take a 90 degree section of each circle. By stating an X” rounded corner, you’re requesting that the edge be installed similar to the outline of that particular circumference.
Under-Form seepage: When a contractor is installing forms on grade, there is a possibility that there may be concrete that seeps out from under the form work. For some, the seepage may occur below the surrounding dirt and there isn’t an issue. In some cases, the under form seepage may be deemed as unacceptable. There’s two paths that the contractor can take to minimize this seepage. One option is to install a base barrier (an oversized garbage bag under the form. The base barrier is pulled up along the outside form work and stapled to the form. After project completion, the forms are pulled off and the contractor cuts the barrier with a razor. The other method is by having a laborer use a cold chisel and knock the excess off the perimeter. It’s likely debatable to opinion, but I feel that the barrier method may be the better approach.
Wash-out: Most contractors will need an area to wash out their tools, wheelbarrows, etc. By designating a “wash-out area”, you’re giving the contractor the direction of the area where concrete may reach the ground. Keep in mind that water saturated with runoff may reach the ground in this area. An additional option is to ask for a barrier to be laid down prior to any runoff. Most contractors are willing to work with you as long as you’re willing to engage in the conversation.
Clean-up: You should always mention that your expectation is for the contractor to clean up all debris, forms, etc. that is related to the installation of the slab. From my own personal experience, I find that I’m rather easy going and wasn’t as worried about the clean-up as the woman of the house. In future endeavors, I’m planning on handing over the contractor’s check to the woman and letting her decide if the site is restored to an acceptable condition. Regardless of gender, you should identify which family member has more of a stake in the anesthetics of the project and have that member oversee the final stage of the installation.
-Mick