Why isn’t water damage from rain a big concern when new homes and buildings are under construction?
In: Engineering
The wood frame is treated wood, it’s not going to get damaged by water in the amount time it’s exposed before the house is done. You just have to make sure the wood is dry before you put up the drywall, which doesn’t happen before a roof is on the house.
If building was dependent on the site being dry the whole time it’s under construction nothing would get built.
It is quite the concern, but stick framing will only absorb so much water so quickly as it has about 12-15% moisture content already. Things like plywood/OSB have a rating about how long they can stay uncovered or get wet before they become unusable, but that lumber is used well before those dates come. Good contractors will also sweep/blow off the water after rains when building the houses.
It is a concern. Thats why we try to avoid wet weather in the time between getting the frames delivered from the factory to to the roof being finished. Sometimes it is not possible and we have to dry out the frames before cladding the house. I was on a job where it rained non stop and the frames still didn’t dry out enough by the time the inspector came around to moisture test, so we stapled on the vapor barrier and rented a bunch of electric heaters and dehumidifiers to heat the house and dry out the timber.
For larger concrete buildings they just let the rainwater run down through the building as new floors are being built up. They just don’t install any moisture-sensitive materials like drywall until the roof is on.
Another user already explained it for stick framing.
While water is a problem in housing especially for wood there are two kinds of water. Water that can easily leave through evaporation and water that can’t leave. The second one is the cause of rot as it gets stuck in contact with wood for several years keeping an area damp. While a building is under construction its very easy to air out, you want to make sure before sealing everything in that it is dry again and everything will be ok. Obs and plywood can have problems with water but tend to be part of the sealing in process of building that happens when it’s dry.
Short exposure to water isn’t a problem. It’s long-term exposure that allows decomposers (primarily various forms of fungus, like mold & mildew) to gain a hold.
So builders generally try to avoid the wettest weather, but if wet weather has been unavoidable then one of the first things done after there is a roof and walls on the building is to put commercial dehumidifiers inside and dry out the buildings interiors.
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