A floor that looks dry after parish flooding can still hold water in the subfloor, the joists and the pad beneath the finish. Surface water is only the visible part of the problem. The subfloor is read with moisture meters and dried until its readings return to normal, and the finish is not laid until then.
Key takeaways
- The surface of a floor dries first, while the subfloor and the pad beneath it can stay wet for much longer.
- Water that wicks up a wall base can wet the subfloor edge and the joists even when the middle of the room looks dry.
- A new floor laid over a damp subfloor can trap moisture and cause the boards to cup or the adhesive to fail.
- Moisture readings at marked points show whether the subfloor is drying, which a look at the floor cannot show.
- Where a raised floor has a space below it, the joists and the underside of the subfloor are read from the access point.
Why does a floor look dry when the water is still in it?
A floor covering can shed surface water and look dry while the materials beneath it still hold moisture. The pad, the subfloor and the joists act as a reservoir, and they release water slowly. A homeowner who judges by the surface alone will often be wrong about how wet the floor still is.
Hardwood, laminate, vinyl and carpet all sit on top of other materials, and each of those materials can keep water. Carpet holds it in its fibers and pad, and a wood subfloor holds it in its grain and its fibers. Once the surface is dry to the touch, the water inside can still be high enough to cause damage if the floor is closed up.
The moisture also moves. Water that is in the subfloor migrates toward drier areas, including the surface, so a floor can feel dry one day and damp the next. Readings at the same points over several days show the trend better than a single touch.
How does water reach the subfloor in a parish flood?
Water reaches the subfloor through the surface, through the wall base beside it, through the threshold and through the space beneath a raised floor. In a flood the water may come from several directions at once, and the subfloor can take water from below as well as from above.
A threshold or a door sill lets water spread across the floor and under the boards at the edge. The wall base then wicks water upward into the drywall and downward into the subfloor. The edge of the subfloor, where it meets the wall, often reads wetter than the middle of the room.
A raised floor can take water into the space under it, where the joists and the underside of the subfloor are wet even when the room above looks normal. A slab floor can take water through the slab edge, and the moisture can rise through the slab into the floor covering above.
How does a crew read a subfloor it cannot see?
The crew reads the subfloor from the surface where the finish is removed, from an access point beneath a raised floor, or from a small opening it makes for the purpose. Moisture meters are used on the subfloor, the joists and the wall base, and the readings are marked on a sketch of the floor.
A small opening in the floor is kept to the size the reading needs. The opening is explained before it is made, and it is closed again once the subfloor is confirmed. The crew does not open a floor on a guess, because each opening adds to the time and the materials.
Where the space under the floor can be reached safely, the crew reads the joists and the underside of the subfloor directly. Where it cannot be reached, the readings are taken from the edges and the access points, and the crew says which points it could not read.
| Where it is read | What a high reading suggests | What the crew does |
|---|---|---|
| Floor surface | Water on or in the finish, or a damp pad under it | Removes or lifts the finish where the pad is wet |
| Subfloor at the wall edge | Water wicked up from the floor or in through the threshold | Opens a small area and dries the edge first |
| Subfloor in the middle | Water spread under the floor from a wide flood | Dries from below where the space allows, or opens the floor |
| Joists | Water in the space under a raised floor | Places equipment under the floor and reads again on each visit |
| Slab edge | Ground moisture or water entering at the slab edge | Checks the ground outside and the slab edge before drying |
Can a wet floor be dried in place, or does it have to come up?
Some floors can be dried in place once the water is removed and the moisture is brought down. Others cannot be saved once the boards have cupped, the adhesive has failed or the subfloor has softened. The crew decides from the readings and from the state of the boards.
Solid hardwood that has taken water at its edges may recover if the subfloor dries and the boards flatten. Boards that have swollen badly, lifted from the subfloor or split along the grain are less likely to recover, and the crew says so. Sealed tile over a sound subfloor can often be dried and kept.
Carpet pad that has soaked is generally removed, because it holds water against the subfloor. Vinyl and laminate that have lifted at the seams may need to come up so the subfloor can be read and dried. The crew explains each decision and shows the readings behind it.
Why is a new floor a risk if the subfloor is still damp?
A new covering laid over a damp subfloor traps the moisture below it, and that moisture can cause cupping, adhesive failure, staining and mold. The subfloor must read dry at the marked points before the new finish goes down, so the damage is not hidden under the new floor.
A floor that is closed up while it is still wet cannot be checked from above. Water that is trapped below a new floor can move slowly toward the seams and the edges, where it shows only after the floor has been in use for some time. The homeowner then has a second problem to fix.
The homeowner can ask the crew when the readings will allow the new floor. The crew can say which materials are ready and which are not, and it can share the readings with the flooring trade so the new work starts from a dry subfloor.
What should a homeowner check during the drying?
Check the floor edge along the walls, look for new soft spots or boards that are lifting, and notice any musty smell. Ask for the readings at each visit and keep the marked sketch. Report any change to the crew, because a new change can mean the drying is not keeping up.
A soft spot that grows or moves is a sign that the subfloor is still wet or has been damaged. Keep heavy furniture off that area until the crew has checked it, and avoid walking on boards that are cupped or springy.
Keep a dated note of what you see. A short record of the edges, the smell and any soft spot, made on the same days each visit, helps the crew see the trend and helps any insurer follow the damage.
How does the drying of a floor fit into the rest of the cleanup?
The floor is dried together with the walls, the framing and the air in the room. The crew sets the equipment so that the air moves across the floor and into the wall cavity, and it checks the floor against the same readings as the rest of the building. A floor is not finished until the whole room is confirmed dry.
Air movers and dehumidifiers dry the room and the floor together. Where the joist space can be reached, equipment is placed beneath the floor to dry the subfloor from below. The two areas are checked on each visit so that one does not finish while the other is still wet.
Drying is one part of the cleanup. Removal, demolition and rebuilding follow the readings, and the floor is one of the last parts to be closed up. The crew explains the order to the homeowner at the start of the job.
What does a homeowner need to know about the cost of floor drying?
The cost depends on the area of floor affected, the floor covering, how far the water reached into the subfloor and whether the floor must be opened. No price is published on this site, and the scope and the cost are confirmed in writing after a walkthrough and before the work starts.
A small area of carpet that dries in place is a different job from a whole floor of solid hardwood that must be opened and dried from below. The number of rooms and the number of boards removed also change the time and the materials.
The replacement flooring is a separate cost and is quoted by the trade the homeowner chooses. The drying and removal in the crew's scope are separate from the new floor, and the homeowner should ask for them to be shown on separate lines.
Frequently asked questions
Why does my floor feel dry but smell damp?
The subfloor, the pad or the space under the floor can still hold moisture, and the smell comes from there. The crew reads the subfloor to find out how wet it is.
Can I lay a rug over a floor that is drying?
Not while the floor is still wet. A rug traps moisture against the surface and slows the drying. Wait until the crew confirms the floor is dry.
Will the subfloor need to be replaced?
Only if it is soft, rotted or delaminated when it is read. The crew records what it finds, and any repair is decided by the homeowner's chosen trade.
How do I know when the floor is ready for a new covering?
When the subfloor and the boards read dry at the marked points, and the crew confirms it in writing. Ask for the readings before the new floor is ordered.
Does wet carpet always have to go?
Not always. Carpet can sometimes be dried and kept if the pad is replaced and the subfloor reads dry. The crew explains the choice from the readings and the type of water.
This guide is general information for Jefferson Parish homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.