What to check before the walls close

Before drywall is not one day, it is three

Between the day the framing is finished and the day the drywall goes up, every pipe, duct, wire and piece of blocking in your bathroom is in plain sight. After that they are behind a wall, and every one of them costs a demolition to reach.

The mistake almost everybody makes is treating that stretch as one walkthrough at the end. It is three, they belong to three different trades, and a question asked on the wrong day is asked too late.

Each of the three days closes something the next one cannot reopen.

Who answers what, and why it matters which day you ask

Nothing on any of the three lists is yours to carry out. Every line is a question, and every question has a person attached to it. Sending all of them to your contractor on one day is how half of them stop being answered.

That last row is the one people underuse. Ask for the published installation document for the exact model that was bought to be on site.

Framing is done: the openings, and the tub that has to go into one

The item that stops a bathroom for a week is the tub opening, because a tub is ordered to a size and the framing is built to the rough opening the maker publishes, which is not the same figure as the nominal length. It is measured stud to stud, before backer board and tile, and it is not adjustable afterwards.

Manufacturer document. One manufacturer publishes an alcove tub of its own as a 60 by 32 inch (1524 by 813 mm) unit, with the drain on one named side, its center line 16 inches (406 mm) from the back edge, and a stated minimum floor load of 45 pounds per square foot (220 kg per square meter). Those are that model, from that document. Your tub has all the same kinds of number on its own sheet.

• Which end is the drain at, on the tub that was actually ordered, and which end is the plumbing roughed in for on the wall as it is today.
• Has the framed opening been measured against the spec sheet of the tub that was actually bought, at three heights and at both ends.
• Has the floor question been asked of the person who answers it, which is your contractor and, where they say so, a structural engineer.
• Does the tub fit through the delivery route, measured rather than estimated.

Order the opposite hand to your plumbing and the fix is a plumber, a floor, or a returned tub.

Rough-in: the valve, and the depth nobody checks

A shower valve is set once, at a height and at a depth. The height is the one everybody discusses in the room. The depth is the one that comes back after the tile is on.

Manufacturer document. One manufacturer's own rough-in sheet for one trim puts the shower arm at 78 inches (1981 mm) off the floor, the valve between 45 and 48 inches (1143 to 1219 mm) for a shower, and at 32 inches (813 mm) for tub and shower combinations. The same sheet calls the depth the critical measurement, sets the finished wall including tile at 1-3/4 inches (44 mm) from the face of the plaster ground, and puts the supply piping center line between 1 and 2 inches (25 to 51 mm) behind the wall surface. Those are that manufacturer figures for that trim. Your valve has its own sheet.

The proof that depth is the recurring failure is not an opinion, it is a product line. The same manufacturer publishes two handle extension kits for exactly this, covering finished walls of 13/16 to 1-13/16 inches (21 to 46 mm) and 1-13/16 to 2-13/16 inches (46 to 71 mm). The kits exist because this happens often enough to be a product.

• What finished wall thickness was this valve set for, tile and backer board included.
• What is the finished wall going to be, measured on the drawing of the tile.
• Is the height the one for the trim that was actually bought, off that trim own sheet.
• Has anyone put the trim against the rough valve to check, rather than reading two documents.

Rough-in: the ducts, and where they come out of the building

The ducts are judged by their route rather than by the box the fan came in, and the route is drawn in these days.

Manufacturer document. One hood maker publishes the arithmetic for its own hoods as a table of equivalent feet: a straight round duct counts 1 foot (305 mm) per foot, a 90 degree elbow counts 15 feet (4572 mm), a wall cap with a damper or a roof cap counts 30 feet (9144 mm), and the total is not to exceed 150 feet (45720 mm) of equivalent duct. The same document states that flexible duct can restrict airflow by up to 50 percent. Those are one maker figures for its own hoods, and the table in your manual is the one that counts.

The fan duct is settled the same day, and its diameter is a manufacturer figure: one manufacturer asks for no less than 4 inches (102 mm) for one of its own ceiling fans, a second publishes an older model using 3 inches (76 mm).

And the question that outranks all of the above: where does this duct come out of the building, and has anybody stood outside and looked at that point. Many US jurisdictions require a bathroom exhaust duct to terminate outside the building rather than into an attic, a soffit or a roof space, and what applies where you live is decided by your building department.

Rough-in: the services behind the cabinets

A vanity or a cabinet run hides its own services. Every line below is easy to move while the wall is open and a demolition behind a finished one, and all of it follows the current plan rather than where things used to be.

• The waste and the supplies come up where the current plan puts the basin or the sink, not where the old one was.
• If it moved, somebody has confirmed the new waste still runs where it has to.
• Water, waste and power for a dishwasher are provided inside the cabinet that will hold it, and not in the one next to it.
• Every outlet and switch has been checked against the tile layout and the backsplash height, not only against the floor plan.
• Nothing lands where a drawer box or a cabinet back will be, checked against the cabinet drawing rather than against memory.

Outlet positions belong on that list too. The code text quoted by the guidelines carries figures for receptacles near a basin, a tub and a shower, required in many US jurisdictions, verify locally. That is your electrician to carry out and your building department to decide, and the point here is only that you ask where the outlets are going while asking is free.

Before insulation: the blocking, and the niche

Blocking costs almost nothing while the wall is open and cannot be added later without opening it again. A grab bar nobody planned for is not a fitting, it is a tiling job.

• The horizontal grab bar, and a vertical bar at the tub or shower entry.
• A seat in the shower, if the plan has one.
• The towel bars and the robe hooks, which pull on a wall the way a grab bar does.
• A wall hung vanity, a wall hung toilet and the frame that carries it.
• A mirror or a cabinet heavier than a screw into drywall.
• The shower niche.
• The jamb of the shower glass, which is the one everybody forgets and the one that ends up anchored into finished tile.

Two published figures describe the wall behind a bar and they answer different questions. The planning guidelines ask for tub and shower walls to be reinforced at the time of construction so that a grab bar can support a static load of 250 pounds (113 kg). One maker separately rates its own hollow wall anchor for a user of no more than 300 pounds (136 kg) and wants 3.5 inches (89 mm) of space behind the wall. Ask your contractor which of the two the wall in your bathroom is built to.

Neither document says how big the framing lumber is or where exactly it goes, and this page does not invent that either. A few of the bar dimensions circulating alongside these come only from an accessibility standard. That standard was written for certain public and commercial buildings, it does not normally apply to a private home, and following it does not make a room accessible.

The niche is a conversation, not a published figure. No planning guideline publishes a height or a size for one. One maker prefabricated niches start at 12 by 6 inches (305 by 152 mm), which is a product range rather than a recommendation. Where it goes and which stud bay it lands in are decided with your contractor, on the wall, before the backer board goes on.

Mark it, do not describe it. Photograph the open wall, mark the blocking on the photograph, and give the marked photograph to your contractor. A list of heights in a message is read once. A marked photograph is on the wall when the work is done.

The wet wall, and the thing nobody publishes a number for

Waterproofing is decided in a conversation that happens once, on the day the backer board goes up, and it is invisible from the day after.

Two published figures apply and they are not the same kind of figure. The planning guidelines recommend a waterproof material extending at least 3 inches (76 mm) above the shower head rough-in. The model code text they quote sets a minimum height of 72 inches (1829 mm) above the finished floor, required in many US jurisdictions, verify locally. The first follows a shower head that you place, the second does not move, and on the same wall they can give different answers.

• What waterproofing system is being used, by name, and whether the whole of it is from one manufacturer.
• How high it goes on each wall, and whether that is above the shower head rough-in.
• What happens at the curb, at the bench and at the niche, which are the three places it has to turn a corner.
• Who photographs it before the tile goes on.

And then the honest gap. Where the toilet drain comes up relative to the vanity, the door swing and the baseboard is not published by anybody, because it depends on the toilet, the vanity and the room. We looked for a figure and there is not one, so this page does not invent one. Instead: photograph the floor with the drain visible and a tape across it, put that photograph next to the bathroom plan, and ask your contractor to mark the toilet, the vanity and the door swing on the photograph rather than on the plan.

The photographs, the last walk, and what you are not doing

This is the set you will want in five years, when somebody asks what is behind the tile. It takes twenty minutes and it is the cheapest thing in the whole project.

1. One photograph of each wall, square to it, with the whole wall in the frame.
2. One of each wall again with a tape extended along it, so the photograph carries its own scale.
3. One of every valve, with a tape showing its height off the floor.
4. One of the ceiling in each room, showing where the ducts run.
5. One of the blocking on each wall that has any.
6. One straight down at the floor where the plumbing comes up.

Name every photograph with the room and the wall letter it shows: A is the wall on your left as you stand in the doorway looking in, and the letters run clockwise. A folder of unnamed photographs is a folder nobody opens, and the set belongs somewhere that is not only your phone.

Look, photograph and ask. Nothing here asks you to open, move, test or work on anything, and the work itself belongs to the trades who are licensed to do it.

This is not a code check and it is not an inspection. What applies where you live is decided by your building department, and your inspection is carried out by the person your jurisdiction appoints. A no on any of these lists is not a failure. It is something raised while it still costs a conversation.