What to put behind the wall before the drywall goes up

Sometime in the middle of a bathroom renovation, the walls are open. You can see the studs, the pipes, the back of the tile on the other side. It lasts a few weeks. Then the drywall goes up, the tile goes on, and whatever is behind that wall stays there for as long as you live in the house.

This is the cheapest week of the whole project, and most people don't know it's a decision point. Here is the one thing I'd put behind every bathroom wall while it's open, what it costs now, what it costs later, and exactly what to say to the person doing the work.

The problem with drywall

Drywall is a half-inch of chalk between two sheets of paper. It holds a picture frame. It does not hold a person.

A grab bar has to take body weight, and not gently. You grab it on the way down when your knee goes, or you pull on it to get up from the toilet on a bad day. The standard most bars are built to says the bar and whatever it's screwed into have to hold 250 pounds of force (STD). Screwed into drywall alone, a bar pulls out of the wall the first time you need it, and it takes a piece of the wall with it.

So a grab bar needs wood behind the wall to screw into. That wood is called blocking.

What blocking is

A piece of lumber fixed between the studs, flat against the back of the drywall, so that when a screw goes through the wall it hits solid wood no matter where along the bar it lands. Some contractors use a two-by-six or two-by-eight on edge. Some use a sheet of three-quarter-inch plywood across the whole wall behind a shower, which is what I'd ask for, because then you can put the bar wherever you turn out to need it (PRACTICE).

While the wall is open, it's a few dollars of wood and ten minutes with a nail gun. Your contractor may not charge for it.

What it costs a year later

After the tile is on, adding the same wood means opening the wall, putting the wood in, patching the drywall, retiling, regrouting, repainting, and finding a contractor willing to come out for a job that small. You pay for the room twice, and you live with a hole in your bathroom for however long the second job takes.

The bar didn't change. The week did.

Where to put it

Put blocking wherever a hand might go when a body is changing position. In a bathroom that means:

• Beside the toilet, on the wall you'd reach for to stand up.

• Inside the shower or tub, on the long wall and the wall with the controls.

• At the edge of the shower, where you step in and out.

• Behind where a shower seat might go, even if you're not putting one in yet.

For height, the published standard puts the center of a grab bar between 33 and 36 inches off the floor (STD). Blocking should cover that whole band, plus a few inches either side, so the bar can go where it works for your body and not where the wood happens to be.

I'd also add it in two places nobody thinks of: beside the bed, at the height of your hand when you sit on the edge, and next to any step inside the house (PRACTICE). You don't have to put a bar there. You're keeping the choice open for a few dollars.

What to say

You don't need to explain any of this to your contractor. You need one sentence, said before the drywall is scheduled:

"Please add solid blocking for future grab bars on these walls, covering 30 to 40 inches off the floor, and let me know before the drywall goes up."

Then one more thing, and it matters more than it sounds. Before the drywall goes up, take photos of every open wall with a tape measure in the frame. Two years from now, when you're ready to put a bar in, those photos tell you exactly where the wood is. Without them, you're drilling holes in your tile and hoping.

If the walls are already closed

Then this week has passed, and that's fine. There are ways to fix a bar to a finished wall. They cost more, they limit where the bar can go, and they're a different post. What you can do today is check whether any other wall in the house is about to close, because the same rule applies to all of them.

The bigger list

Blocking is one of about fifteen things that disappear behind the drywall in a renovation. Doors, outlets, the shower valve, where the drain sits, the width of a hallway. Every one of them is nearly free while the wall is open and a construction job afterward.

I wrote a short free guide to which decisions close when. It's called The Decisions Your Renovation Makes Without You, and it's set in large print so you can read it on a bad day. Sign up and the download is yours.