This article will focus on a Gypsum Overpour application when installing a radiant heating system. All the pictures and videos used here are our own from a project for Will Gonell, with tubing and manifolds installed by Blackrock HVAC, and the overpour installed by Mack Constructions Inc.

WHAT IS GYPSUM OVERPOUR?

Many Toronto homes like this one are removing old cast iron radiators and creating more room by installing/hiding the heat source into the floor. In the case of new construction, the gypsum overpour is already calculated into ceiling heights. Gypsum overpouring can be a cost-effective and efficient way to create a smooth, level surface for finished flooring, especially in situations where the subfloor is uneven. However, it is important to ensure that the subfloor is structurally sound by consulting with your structural engineer, and free of any moisture issues before applying the overpour.

The overpour is usually around 1 1/2 inch thick, and it can be used with a variety of finished flooring materials, including carpet, vinyl, wood, or tile. The gypsum material used is a self-leveling light-weight compound that is mixed and poured onto the prepared subfloor. The gypsum compound is typically fast-setting and can be walked on within 24 hours after application, allowing you to quickly get back to construction.

WHAT ABOUT THE HEATING PIPES?

Before beginning the overpour there’s work to do. Your framer, heating contractor, and gypsum team need to be on the same page. The framer should be installing double bottom plates for all the walls to accommodate for the 1.5″ of gypsum. This allows a 2×4 to still be there for drywall and baseboard installation. Just before our team were scheduled to install the tubing, the team at Mack Constructions Inc did a fantastic job prepping the floor with a plastic sheet and a foam perimeter so the self-leveling compound stays within the area and doesn’t escape through all sorts of cracks. Your heating contractor then needs to install the loops using staples or PEX clips and not leave the site until it’s all pressure tested.

The advantage of using the staple-down method is that it provides a secure and reliable method of installing the radiant heating piping. The staples hold the pipes in place during the pouring of the gypsum overpour, ensuring that the pipes do not shift or move. A common newbie mistake is to not use enough staples. This creates a tripping hazard AND the piping will actually lift and float on top of the overpour causing a headache and panic.

The staple-down method is a common way to install radiant heating piping before pouring gypsum over the top. In this method, the radiant heating pipes are stapled to the subfloor to hold the pipes in place. The radiant heating piping is typically installed in a serpentine pattern, but at Blackrock HVAC we do it better and try to always install them in a reverse-return pattern. Once the pipes are in place, a pressure test is always performed to ensure that the system is free of leaks, and to sound an alarm incase the tubing gets accidentally punctured during the overpour process.

It’s important to note that the use of a plastic slip sheet is not always necessary. On occasion, you will pour on a plastic slip sheet and/or styrofoam insulation, but more often, you’ll pour “bonded,” where a primer is supplied and installed to the existing floor just prior to the pour to enhance the bond between the gypsum concrete and existing structural substrate. The primer also helps to decrease moisture penetration in the existing subfloor. Ultimately, the choice of whether to use a slip sheet or bonded method depends on the specific jobsite conditions and other factors that may be present.

WHAT TO DO IN THE BATHROOMS?

Typically bathrooms take up very little square footage and they don’t require their own heating loop unless it’s a large ensuite. In this project, we ran a bedroom loop inside the one of the smaller bathrooms where your feet would be, and a separate loop for the ensuite. You can skip installing pipes under the vanity since it won’t have a noticeable effect. Wether or not to install it under the shower needs to be discussed with the builder. It depends on their plan for the shower floor, here we skipped both showers.

THE MANIFOLD LOCATIONS

The use of a water manifold allows for precise control of the flow of water to each individual loop of tubing in the radiant heating system. This allows for greater flexibility in controlling the heat output of the system and can help to improve overall efficiency. It is important to ensure that the water manifold is installed correctly and that all connections are properly tightened and secured. That’s all obvious. What isn’t obvious to some are how and where to install them!

1. Consider hiding the manifold and tubing connections inside a closet to optimize space. Since your mechanical room is likely already crowded with equipment and located far from the upstairs manifold, installing a separate 3/4″ supply and return from the mechanical room can save over 100 feet of 1/2″ tubing. Ideally, have your framer construct one closet wall using 2×6 lumber.
2. To prevent hot spots near the manifold, it is important to insulate the tubing in the vicinity. While your furry friend may enjoy the warmth, it may not be comfortable for the human occupants of the room. To ensure proper insulation, extend it a few feet away from the manifold and organize the pipes neatly.
3. Embrace the opportunity to add style to even the most hidden parts of your project! At Blackrock, we believe that attention to detail is key, even when it comes to the interior of a closet wall. In this project, we took a creative approach by painting the plywood black and installing perforated aluminum sheets behind each manifold. The result is a visually stunning effect that adds a touch of sophistication to the home, even in areas that are typically overlooked.

TIPS FOR A SUCCESSFUL PROJECT

As a company that specializes in installing overpour, Mack Constructions Inc offers their clients essential prep work to ensure a successful project. They provide and install the floor primer and discuss the predetermined heights for features such as staircases, windows, fireplaces, and door heights with the client to avoid confusion. Mack Constructions requests to seal all gaps and holes, which is outlined in their quotes and discussed with the client. However, their team will still ensure that it is done sufficiently to their standards to prevent any leaks to the floor below. During the actual pour, their team checks that the correct mix ratio of sand, gypsum product, and water is used to achieve a consistent and strong mix throughout the entire job. Their goal is to provide a smooth floor surface for every client!

At Blackrock HVAC, we believe that working with other companies that have a proven track record of successful projects makes all the difference when it comes to hiring us. With our experience and expertise, we can easily collaborate and work with other teams towards a common goal!