In a previous article (October 2006), we discussed substrate preparation and material selection. We will continue this discussion with material installation.
Self-Leveling Materials FlowOnce the substrate has been deemed to be sound, clean and properly profiled, one final step is required prior to priming. Self-leveling materials are very flowable. Therefore, holes or gaps that would allow the SLU to run or leak must be filled or sealed. Patching compounds and caulk are most often used. Floor drains and other cut outs must be sealed and protected. Duct tape and plastic can be an effective barrier.
JointsIdentify and maintain, or create joints where appropriate. Expansion (isolation) joints are designed to move. Walls and columns are good examples. They will move differently than the floor slab and must be allowed to move independently. Therefore, do not bond to the wall or column and maintain or create a joint. Plastic sheeting may be hung to help create this separation. When the SLU has hardened, cut the plastic at the surface. A ¼” gap is suggested for the expansion joint.
Helpful Hint: Hanging plastic can also be a part of the protection of the wall from splatter of the SLU.
Most manufacturers of SLU recommend maintaining control joints. Control joints will often telegraph into the new layer. The most common way to maintain control joints is to re-cut the joint once the SLU has hardened. Maintaining a clean crisp joint is very important when installing a self-leveling wearable topping.
Plan the PourRegardless of the size of the job, give some thought to the layout of the area and how the floor will be poured. The very first question to ask should be, “Is the goal to truly level the floor or simply smooth it out?” There is a significant difference. The floor may be very rough and the profile is unacceptable. Self-leveling can be the most economical method to correct this problem. If the levelness of the floor does not meet the floor covering’s requirement, the installation has just become more costly. Different floor coverings will have different tolerances. For example, ASTM F710, Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring, recommends that the surface to be flat within 3/16” in 10 ft. The TCA recommends ¼” in 10 ft. Be careful to follow the floor covering recommendations. Floors from edge to edge may be out of true level by 1 or 2 inches. Is complete levelness required?
Other questions need to be addressed. Is the entire floor to be poured or an isolated area? What is the working time of the product? What is the logical maximum width of the pour? If this is an occupied area, what will remain that needs protecting – woodwork/ trim, walls, windows, etc? Is the installation to be completed in one pour or is it a large open area that will require multiple pours? Are there elevation issues at doorways?
When preparing the area for leveling, consider those things that have an effect on the performance of the material. The temperature should be controlled. Warm temperatures will reduce working time. Most manufacturers agree that the ideal temperature range is 60 – 80 degrees. Prevent premature drying by closing doors and windows which will prevent significant air movement or wind. Direct sunlight can also be a problem. Plan the pour so that you are unaffected by direct sunlight through that large bay of windows.
Floor LevelingSo, levelness is an issue. The best way to attack this problem is with the use of a laser. Identify high spots on the floor. Set the laser on the floor and project a line onto a target or two across the room. On a small area marking the wall may be sufficient. Larger areas will require the use of pins to set a grid across the floor. Screws, nails, or plastic pins may be used. A plastic pin is easily snipped or cut at the laser identified spot. Pins are usually set every 3 square feet or so. The material is then placed to the tops of the pins. This is a time consuming process. Make sure that you are being fairly compensated.
ToolsThe following list of tools helps to achieve a successful installation:
Mix Barrel (minimum 10 gallon capacity), Mix Paddle )appropriate for barrel), and ½” drill or Mixer & Pump
Screed or Gauge Rake
PlacementThe substrate is prepared (clean, profiled, patched and primed) and the jobsite is secure. You are ready to place the material. Select the best location for a mix station. If mixing by pump, this location will likely not change. If barrel mixing, try to make it so there is little travel time with the mixed material. This station may move as the floor is being placed. What is the source of water? Be sure that water temperature is appropriate. If the water hose runs outside in the sun and warm water is delivered, working time and workability will be reduced. Keep the water cool. Bags of ice in mix water will do wonders.
Be very careful to follow the manufacturer’s recommendations for water demand. Too little water will result in lack of flow and heal and too much water can result in a dusty, weaker product. If mixing by barrel, use a device that will be consistently accurate. Pour the water into the barrel and then slowly add the powder. Mix the material. Take care to scrape the sides to ensure that all the material is mixed. Do not use an up and down motion where the paddle is pulled out of the material. This will result in excess air in the product. On the pump, dial in the water demand and double check it throughout the pour. As material is delivered to the floor, check consistency. It may take a couple of bags to produce the desired flow. It is important to time the delivery of material so that it is consistent.
Begin the pour in the low corner. Pour the product in an even ribbon across the floor. Pour a sufficient bead that can easily be worked. Do not dump into a pile because it will be difficult to move. Then use a gauge rake to help set the depth of the pour. The next pass of material is poured up against the previous. It is very important to maintain a wet edge. This will help the material create a smooth transition. The screed or smoother may be used across transitions to assure perfect mergeing.
Pull the smoother across the pour. The smoother will break the surface tension allowing the material to relax, heal, and allow any entrapped air to release. One or two passes may be needed with the smoother and then move on. Do not over work the material. From time to time air bubbles may appear. If this becomes troublesome, check to make sure that the substrate is properly primed. Also, a spiked (or porcupine) roller can help knock out the air. Some may prefer to use the smoother after the spiked roller to alleviate the dimpled appearance.
If forming is needed to end your pour or to tighten the width of the pour, a 2-by-4 may be used. Either screw into position or place bags of material on it to temporarily hold in place. Another approach is to use insulation tape or weather stripping. Pull the form and pour to create a smooth transition.
As previously mentioned, check the elevation at doorways. If not pouring past the door or if the door does not allow the entire pour thickness, stop the pour a foot or two away and beyond the door’s swing if in that direction. Either feather the edge with the SLU or plan on creating a smooth transition with a trowel applied patch once the SLU has hardened and dried.
If deep pockets exist on the floor consider pre-pouring these areas. For most SLU, once the depth is greater than one inch, they may be extended with larger aggregate or pea gravel. Check with the SLU manufacturer on their specific recommendations. In many cases, weigh up ½ the weight of the SLU bag and slowly add it to the mixed product. This mix will not flow so you will have to work to move the product into place. Another option is to pre-place about 1/3 to ½ the desired thickness with pea gravel on to the prepared substrate. Pour the SLU into the pea gravel and then use a stiff broom or rake to work the product into the pea gravel ensuring complete consolidation. Either continue to pour up to the desired level or let the material harden and re-pour. When re-pouring it is important to prime the original pour.
It is important to keep other trades off your work. Coordinate schedules and give them notice of when you will be pouring a certain area. Keeping good relations can help make a successful application. Also, schedule the pour so that you leave yourself an exit. You will need an area to clean up your mixing equipment. It’s always wise to have a couple empty 55 gallon drums to pour out waste.