Norcross structural drying, explainedfrom wet framing back to normal

Structural drying is the controlled process of getting moisture out of a building's materials: studs, subfloor, joists, drywall, plaster and slab. Once the standing water has gone, what remains is water inside these materials, and that water leaves in only one way. It evaporates into the air, and then the air has to be dried or replaced.

Three things move that process along: air movement across wet surfaces, low humidity in the room and a reasonable temperature. Air movers supply the first, dehumidifiers the second and, where needed, heat the third. Getting the balance right is what separates a controlled job from a hopeful one. Too little dehumidification means the air simply soaks up water and passes it to dry rooms; too much heat without it can make humidity worse.

The word "controlled" matters here. The process has a measured start, a daily check and a defined finish, set out in the industry's ANSI/IICRC S500 standard. ^[5] What decides whether the job is finished is a moisture reading compared with a dry reference, not the date on a schedule.

Relative humidity is a measure of how close air is to holding all the water it can at that temperature. When the air is nearly full, water in materials has little reason to leave. On a muggy Norcross afternoon, that is the condition just outside the door. Opening up the house to "air it out" brings in that heavy air, and can raise the indoor humidity rather than lower it.

Experienced operators work with a closed building for this reason, using refrigerant or low-grain dehumidifiers to pull water out of the air and pipe it to a drain. In cold, drier winter spells, things are reversed somewhat: outside air may help, yet cold rooms slow evaporation and many dehumidifiers lose efficiency, so a contractor may have to add heat. Good practice takes a reading rather than assuming either way.

The EPA suggests keeping indoor humidity below 60 percent and ideally between 30 and 50. ^[1] During a drying job, the room itself is usually pushed lower, for a time, in order to pull the moisture out of materials more quickly.

Much of Gwinnett's housing is suburban frame construction, including crawl space homes and those with daylight lower levels. A two-level home built into a slope has one side against the soil, so a wet wall there may keep taking on moisture from outside unless the exterior drainage is addressed. Crawl space homes add a second problem: damp air under the floor can feed moisture back up into the joists even after the rooms above have been dried.

Downtown Norcross is different. The National Register district at the heart of the city lists 194 contributing buildings, with late Victorian and revival styles among them. ^[2] Some of those homes have plaster, old wood floors and wall cavities that behave differently from modern drywall. Drying has to be slower and more careful, and aggressive cutting may be neither needed nor welcome. Multi-family buildings along Buford Highway pose another challenge, because a dehumidifier in one unit cannot deal with moisture moving through shared floors and walls. ^[6]

Long rainy periods add to all of this. Atlanta's annual total varies widely from year to year; the National Weather Service recorded 66.99 inches in 2020 and 53.81 inches in 2021. ^{[3] [4]} A wet spell during a drying job can stretch the timetable simply because the building is fighting damp air at every opening.

A proper handover includes the log of readings, showing each measured point coming down to the target. You should be able to see where the dry reference reading came from. If readings are not available, or if equipment is being removed although some are still high, ask why. Sometimes materials are being removed instead of dried, which is reasonable as long as you are told.

The feel of a surface is a poor guide. Paint films and tile can stay dry while a wall behind them is wet. Temperature can mislead too: a dry-feeling room may simply be warm. Thermal images can help find remaining cool, damp areas, but they are a way of deciding where to take a reading, not a replacement for one.

High-speed air movers can spread whatever is in a room. If there is sewage contamination or visible mold, the area needs containment and cleaning first, and an air scrubber may be used. Ask how they will prevent contaminated air travelling into clean rooms, and whether your heating and cooling system should be shut off while this happens.

Old materials need attention too. Disturbing paint in a pre-1978 home can raise lead concerns, and federal Renovation, Repair and Painting rules apply to certain paid work. ^[7] Many historic Norcross homes are well within that age range. Older insulation, flooring and joint compound can also contain asbestos, so ask about testing before anything is cut or sanded.

Drying in place makes sense when the water was clean, the job was started early and the materials are structurally sound. Hardwood, plaster and built-in cabinetry are often worth the extra effort. Removal tends to be the better choice when materials are contaminated, have lost strength, are holding wet insulation or have been wet so long that mold is likely.

A good contractor will explain the choice in terms of water category, readings and the condition of each item. The decision should not be automatic in either direction. The soaked drywall guide on this site walks through the most common version of this question.

A big house with one wet room does not need the whole building dried. Contractors often hang plastic sheeting to make a drying chamber around the wet area, so dehumidifiers work on a small volume of air and equipment is not wasted on rooms that were never wet. Containment also limits dust, and it keeps moist air from moving into clean areas. If there is sewage or mold involved, it serves as a safety barrier as well, usually with filtered air exhausted from the space.

You may see a zipper door taped to the plastic and hear the sheeting pull inward as the air moves. Ask the contractor to explain how you get through the house while this is up. Bathrooms and kitchens may be inside the chamber, so that conversation is worth having at the start rather than on the second evening.

Whether to run central air during drying depends on what happened. If the unit and ducts stayed dry and the water was clean, cooling can help hold down humidity in unaffected rooms. If water reached the air handler, or if a duct in the crawl space or attic got wet, the system could spread moisture and contaminants, so it should be checked first. Contractors often close supply vents in the drying area to keep a chamber stable.

Wet ductwork is easily missed. Flexible duct with soaked insulation usually needs replacing, and sagging runs in a crawl space may hold water. Ask the contractor or an HVAC technician to inspect any ducts in the affected area before the job is signed off, and replace the filter after equipment has been running for several days, because the dust load is often unusually high.

Base cabinets are a classic trap, because the toe kick hides a closed space above a wet floor. Contractors can remove the kick and blow air in, or drill small holes in a hidden location and inject dry air. Upper cabinets rarely need any of this, unless water came from above. Bathroom tile over cement board is slow to give up water behind it, and shower pans may need to be evaluated by a plumber if they were the original source.

Vinyl flooring, sheet goods and thick laminate act as vapor barriers that stop the subfloor from drying upward. They may have to come up even when they look undamaged. Wallpaper and oil-based paint on an older wall create a similar barrier, which is one reason a wall may stay wet longer than the equipment plan allowed for. The decision to remove finish or to wait should be based on readings over a couple of days.

Drying a shop, office or apartment follows the same physics, but the planning differs. Equipment may have to work around trading hours, and electrical circuits may not be available in the amount a large setup requires. Multi-unit buildings need someone coordinating access to several homes, because a wet wall may be shared with a neighbour who has not noticed anything. It helps to keep a separate log for each unit.

Owners and managers should decide early who communicates with tenants and how. Short written updates on what has been done and when equipment will leave can prevent a lot of confusion, particularly in a building with several households or several languages.