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There is a new house under construction near me. I pass it daily. The foundation is done and they are working on framing now. We had a big storm recently, and so all the framing and presumably the basement were exposed to the elements. How do builders mitigate water damage from weather before there is a roof?

I am imagining all the boards warping, or harboring mold, or a foot of wet snow in an exposed basement.

I don't know much about construction and I can only share what I see as I drive by, but still it makes me wonder.

Peter Mortensen
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nuggethead
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    It will dry out before they finish, if construction proceeds at the normal (glacial) pace... – Jimmy Fix-it Dec 22 '22 at 03:40
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    Wood gets wet; wood gets dry. Wood that’s been nailed into a structure doesn’t warp much. If it does, the taper will fix it. – Aloysius Defenestrate Dec 22 '22 at 03:46
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    Not many buildings are perfectly square, vertical or straight… – Solar Mike Dec 22 '22 at 06:23
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    The big problem is the subfloor. Depending on what material they are using, standing water is bad. OSB subfloor will start to swell and plywood will start to delaminate if the water isn't addressed quickly. Fortunately there are waterproof subfloors now where it doesn't matter (roof decking too). – RetiredATC Dec 22 '22 at 06:55
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    On the subfloor... In my son's new house, they installed the plank flooring before the subfloor had a chance to thoroughly dry out. Result was several day of re-work to fix cupping and bowing problems. – SteveSh Dec 22 '22 at 15:18

5 Answers5

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The ultimate goal in construction is zero water intrusion, and they're not using treated wood. This seems counter-intuitive. Why would you expose framing lumber to water?

The answer is simple: limited water exposure will not hurt the wood.

Water will inevitably destroy wood. Wood is porous and will readily absorb water like a sponge, causing it to expand. Sooner or later, the water will evaporate and the wood will shrink back down. It's this constant process that will inevitably destroy even pressure-treated wood. It's why waterproofing on a regular basis will extend the life of the wood.

How do builders get away with this without pressure-treat or waterproofing? It takes months (or years) for this process to take hold, and typically the framing and OSB are only exposed for a few weeks at most. Watch the color of the wood. The yellowish color fading to grey is the first sign that water damage is happening. I bet none of the wood even fades a little before they enclose the walls and put a membrane on the roof.

What about termites? Termites need for the wood to remain wet for them to dwell there. Remove the water and the termites will usually move on in short order. The rain won't last forever and the finished house should not provide them any water sources.

Machavity
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How to prevent water damage during construction

Don't expose construction to water.

How do builders prevent water damage during construction?

They don't; at least not in regards to framing and the foundation. A foundation literally sits in wet dirt, a little rain isn't going to do anything.

Framing is allowed to get wet but electrical, sheetrock, and insulation is not. That's why construction happens in steps. Interior work basically has to wait for windows and a roof.

A plywood subfloor should also wait for a roof at minimum.

The house you live in underwent the same exposure to elements when it was being built.

MonkeyZeus
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    Subfloors can't wait for a roof. Modern framing has the walls of each level built over it. We routinely drilled drain holes in OSB subfloor and used used drum sanders to flatten out swollen joints once the roof was "dried in". Otherwise it's not a problem in climates with intermittent rain. – isherwood Dec 22 '22 at 14:22
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The next day standing water is swept off. It takes a lot for water to get deep into wood. Once a house is dried in humidity is addressed. Often it isn't big rains that cause problems is a lot of little bad habits that build up the moisture content in materials.

Sparks McGee
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One way is to wrap the building, as we did. This sped up the construction time and prevented damage to the framing.

I am not sure if this is worldwide. Some years ago, New Zealand moved from the tried and tested way to treat framing timber by dipping. At this point in time, it was sprayed on and was supposed to last a few weeks in the rain. Less, if you have made any significant cuts to it. In New Zealand, we have all 4 seasons in one day. Realistically, the framing could stay in the weather getting rained on for a couple of months.

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The slot/flap you see, is for materials to be delivered in from outside.

Rohit Gupta
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Interesting discussion! We're in the NW and it has been almost non-stop rain, very heavy storms at times. Our house is currently getting an addition and parts of its west wall have been demoed and are sealed by plywood and tarps, with tarps on roof and side of house too. Subfloors are in and wall framing too + some roof trusses. Roofline between trusses has been demoed and temp shingles applied. The crew has not been tarping adequately -- there are huge gaps and holes in the tarps, and sometimes tarps have blown up or off. The roof edge didn't have proper flashing or other water diversion until today when we got other advice and insisted it be added + a huge hole-free tarp.

Anyway, consequently, our subfloors have gotten very wet, repeatedly, and sometimes have become saturated. They are rated for 6-months in the elements, but water has been pooling -- we sweep it off whenever possible. Wood is still the normal, fresh color, but one spot is starting to peel a little. Roof should be done within the week. We also had water intrusion last night, dripping through windows and French doors around the demoed roof side. Internal wet areas will be demoed later, but we're worried about the amount of moisture that may be inside walls that we'll be breathing for a few months, and repeated exposures on subfloors and framing. Hoping dry-in can solve most of these issues. Any other advice would be appreciated. Thanks to all for what you've already shared!

EDIT TO ADD: Sub-floors have been exposed for 3+ weeks now and framing for 2+ weeks

user180459
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