It is important to seal your toe ups in order to stop the flow of air through your walls. This is not the same thing as “breathing walls” which we straw balers like to talk about as a good thing. That is entirely different. In a breathing wall, the concept is that air, pressurized from the interior of the house will slowly make it’s way through the walls, starting with the interior plaster, moving through the bales and finally escaping through the exterior plaster.
That’s all good because the interior plaster removes the majority of the moisture from the air and releases it slowly, back into the room, and through into the bales. It does that release in a slow and controlled fashion, so the system stays in balance. More on this process at another time. This blog post is about something entirely different: stopping moisture laden air from moving directly from the interior, conditioned space, into the bales.
The most common places for such infiltration is through the back of electrical plugs and other wall penetrations, at joints around partially exposed framing (picture interior timber frames exposed, yet also in contact with the plaster), and the floor to wall joint. For the back of the electrical plugs, either use a sealed electrical box typically used in exterior installations or shoot some minimally expanding foam into the box after the wiring has been completed but before the switches and plugs have been set. For the joint along the timber frame, be sure to reinforce the plaster with blood lath where it meets the wood and then consider using either a bead of caulking after the plaster has been applied and has cured, or a seal similar to the one used at the floor to wall joint.
As you can see in the picture above, the floor joint is covered with an adhesive flashing that folds from the floor to the toe up, sealing the gap that would otherwise be left to move moisture into the walls. This works very well, but there is one draw back…okay, maybe two. First, the floors and toe ups have to be very clean to allow the material to stick and seal the joint properly. That’s hard to accomplish on a job site. Secondly, if the floor is finished slab, or some other finish material, you risk installing the adhesive material where it will be seen or leave a sticky residue on the floors.
A material I like to use in place of the adhesive flashing is a sill sealer. It’s a simply roll of foam that is installed underneath the toe ups at the time of their initial installation. Because it is a malleable foam, it fits any shape (within reason) and seals it tightly. It’s also really easy to install, and the floors don’t have to be so clean you could eat off of them either.
Sealing these areas will increase your building envelope’s efficiency greatly and will extend the life of your bales. Two really good things to have in your house and for your peace of mind.