What type of drywall compound works best in Toronto's humid summer conditions for taping and finishing?

Setting-type compound (commonly called "hot mud") is the best choice for drywall taping and finishing during Toronto's humid summer months, because it cures by chemical reaction rather than evaporation and is therefore far less affected by high humidity. Pre-mixed all-purpose and topping compounds rely entirely on moisture evaporating from the compound into the surrounding air — and when that air is already saturated with humidity during a GTA summer, drying times can double or triple, delaying your project and increasing the risk of mould growth in the wet compound.

During July and August in the GTA, indoor humidity in homes without air conditioning can easily reach 60–80%, especially in basements and rooms without adequate ventilation. At these humidity levels, a standard coat of pre-mixed all-purpose compound that would normally dry in 12–16 hours can take 24–36 hours or longer. In poorly ventilated basements — the single most common drywall project location in GTA homes — the compound can remain damp for days, creating ideal conditions for mould growth right inside your wall joints before the project is even finished.

Setting compound solves this problem. Products like CGC Easy Sand and Durabond are sold as dry powder that you mix with water. Once mixed, the compound sets through a chemical reaction (similar to how plaster sets) in a predictable timeframe regardless of humidity. Easy Sand 45 reaches its initial set in approximately 45 minutes, Easy Sand 90 in about 90 minutes, and Durabond 90 in roughly 90 minutes. This means you can apply a coat, let it set, and apply the next coat the same day — even in the most humid GTA summer conditions. A professional finisher using setting compound can complete all three coats in a single day, whereas pre-mixed compound in humid conditions might require three separate days with overnight drying between coats.

Choosing the Right Setting Time

For the bedding coat (first coat over tape), Easy Sand 45 or 90 is the most practical choice for GTA summer work. The 45-minute version gives experienced finishers enough working time to tape a room before the compound starts to firm up, while the 90-minute version provides a more relaxed working pace that suits homeowners attempting DIY taping. Durabond in the same set times also works well for the bedding coat, but Durabond sets much harder than Easy Sand and is significantly more difficult to sand — a consideration that matters greatly for the finishing coats.

For the second (fill) coat, Easy Sand 90 is ideal. It gives ample working time for building out the joints and feathering the edges, and it sands reasonably well once set. Avoid using all-purpose pre-mixed compound for this coat during humid summer conditions — the thick fill coat takes the longest to dry and is most vulnerable to humidity-related problems.

For the final (skim/finish) coat, you have two good options during GTA summers. Easy Sand 210 (the longest setting time) provides a smooth, workable consistency similar to pre-mixed topping compound, with enough open time for careful feathering and finishing. Alternatively, if humidity is moderate (below 60%) and you have air conditioning or a dehumidifier running, pre-mixed topping compound (CGC blue-lid) can work well for the final coat — it sands more easily than any setting compound and produces the smoothest finish. Many experienced GTA finishers use setting compound for the first two coats and switch to pre-mixed topping for the final coat, running a dehumidifier to manage drying conditions.

Practical tips for summer finishing in the GTA. Run a dehumidifier in the room during and after compound application — even when using setting compound, a dehumidifier helps with the residual moisture that needs to evaporate after the chemical set. Keep the space at a consistent temperature with air conditioning if available; cooler temperatures (20–22°C) slow the set time slightly but produce a stronger bond. Mix setting compound in small batches — once mixed, you cannot extend the working time, and throwing away hardened compound in the mixing pan is expensive and wasteful. Clean your tools immediately after each batch, as hardened setting compound is extremely difficult to remove.

One important caution about mesh tape and hot mud. If you are using fibreglass mesh tape (self-adhesive), you must bed it with setting compound — never with pre-mixed all-purpose. Mesh tape relies on the superior bonding strength of setting compound to resist joint cracking. Paper tape works with both setting and pre-mixed compounds, making it the more versatile choice. Most GTA professionals prefer paper tape for all applications, reserving mesh tape for quick patches and repairs.

For homeowners tackling summer drywall projects in the GTA, Easy Sand 90 is the most forgiving all-around choice — it gives adequate working time, sets reliably in any humidity, and sands well enough for competent finishing. A bag of Easy Sand 90 runs $15–$22 at GTA building supply stores.