Houses get rained on all the time while being built but why is there no continuing mold problem after this?
In: Engineering
Lumber used in home construction is almost always sealed and treated with biocidal compounds like copper that not only naturally repel/kill pests such as termites but also inhibit the growth of mold or mildew as well.
Additionally, mold requires a favorable environment to grow- dark, warm and damp. This is why showers or bathrooms are often where you find it. That environment doesn’t persist for a home frame under normal circumstances, even after being rained on. So mold is unlikely to thrive there.
Mold and rot and the like take a while to become problematic.
The building envelope goes on the frame fairly soon after the frame goes up, which does not take long. It can only soak up so much water – most rain will just fall off the frame. After the envelope is on they leave the building alone for a bit so the wood can dry out – how long this takes depends on the local climate and how much the wood got rained on during construction.
Once it dries out enough they start putting the finishes on.
The only wood that is pressure treated are the piece that are in contact with the ground or the concrete slab they build the house on, or trim pieces that are exposed to the weather. The rest is just Dey lumber, often kiln dried, and can just handle a bit of rain for a few days before the building gets waterproofing on.
They dry out. Once you wrap the frame in a weather barrier like Tyvek, install the windows… that prevents the inside from getting wet while any residual moisture is able to dry quickly before the drywall goes up.. It only becomes moldy when moisture/dampness festers for a long time. A few days or rain and then it drying out quickly isn’t enough for that to happen.
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