How Do You Properly Seal 2 Containers Where Their Center Pieces Are Cut Out?

. The method we use to create a seal is with roofing cement, thin sheets of metal and welded corner posts. Once the two containers have been set side by side on their foundation then you can begin to weld the units into the foundation and the adjoining corner posts. Before applying the roofing cement you must first install the rolled roof flashing inside and outside the opening. The combination of these three should create a perfect seal.

On some other homes we use "backer rod". Backer Rod is sold in most hardware stores and is very inexpensive. It can be found in the plumbing section and is sold in different thicknesses.
We stuff this in the gap of the container and then squeeze in Duritan. This is a sealant sold in Costa Rica. In the states you will want to ask your local store which material is the best to seal these boxes. They will have exactly what you need and all you will have to do is apply the substance on top of the backer rod.