This Old House S47 E25: Walpole ADU Luxury Vinyl Plank, MDF Wainscoting, and 12 Smart Switches in the Snow

A blizzard dropped 21 inches of snow on Walpole, Massachusetts, and the two-building project on that 1970 ranch kept moving anyway. Season 47, Episode 25 is built around three subjects that don't normally share a page: how luxury vinyl plank is manufactured, an MDF wainscoting assembly in a mudroom, and a smart lighting system that runs on ordinary wiring. The connective tissue is material selection. Every choice in this episode is an argument about where a durable, low-maintenance product earns its place and where it doesn't.

Kevin O'Connor also delivers the ceiling on the ADU: 900 square feet, which he says is the maximum Massachusetts state law allows. That number matters for everything downstream, including why the laundry room has a full-size washer and dryer and why the second bathroom had to be shoehorned into leftover space.

Walpole After 21 Inches: Two Buildings, One Snowbank

The ADU is well past framing now. Cabinets are in, full-size appliances are sliding into place, and the quartz counters are still on order. Dan walks Kevin through the mudroom and laundry, which does double duty with a utility sink alongside the washer and dryer hookups. Dan's reasoning is practical: his father-in-law comes in from the yard covered in grass and dirt, and the sink is right there. "If you make the in-laws work, they should also be clean," he says. Hard to argue with the logic.

The partition wall separating the ADU from the bonus space and the original house is the same firewall assembly from earlier in the season, mineral insulation and extra-thick drywall, and Kevin points out that it's still doing its job. That assembly was the main event in the E24 post on the firewall recipe and the Dorchester attic ADU, where a rated wall between two dwellings under one roof stopped being an abstraction.

Inside the main house, the primary suite has been rearranged since the demo phase. The wall Kevin cut through a couple of months back added about 10 feet for Jill's closet; Dan gets his own. A small half bath got infilled and turned into a linen closet. The bath itself now has a double vanity, dual showerheads, and radiant floor heat. Nobody is sharing anything anymore, which is roughly the point of a renovation like this one.

Inside the North Georgia LVP Line

The factory segment is the most useful 10 minutes of the episode, mostly because it answers a question most flooring aisles don't. Luxury vinyl plank is PVC plus calcium carbonate, and Daniel Green, the plant's director of operations, says the limestone runs 50 to 60 percent of the formulation. Kevin notes that PVC is already familiar territory: siding, windows, doors, pipe.

Here's the part worth remembering. The extruder pushes that blend through a slot die, and two nip rollers control the gauge. The line runs a 4-millimeter product, starting around 5 millimeters and compressing down, which Daniel says improves density and impact resistance. Cooling fans handle the rest. Edge trim brings the sheet to roughly a 1/8-inch tolerance so it yields exactly seven boards across. The trim waste gets ground up and fed back into the formulation, which is a reasonable thing for a product sold on cost to be doing.

Printing is where the older method falls apart and the newer one doesn't. Offset printing lays color down with a roller, and you're limited by the circumference of that roller, which typically means the pattern repeats every seven boards. Direct digital printing sprays each pattern instead, and this line produces 35 unique planks, about 80 square feet, before anything repeats. Wood doesn't repeat. That's the whole trick.

The print line itself runs cleaning station, primer (which Daniel confirms is paint, not ink), a putty station for filling extrusion imperfections, then UV lamps. Kevin asks about VOCs and gets the answer you'd want: solvent-free, UV-cured, low VOC. The wear layer is multiple passes of aluminum oxide, which Daniel calls the second-hardest mineral on earth, right behind diamond. An Evertuff topcoat adds stain, chemical, and fade resistance. Profiling cuts the click edges with a six-blade setup, male on one side, female on the other, and the sound-deadening pad is already attached to the back.

Two Floors, Two Different Arguments

Jay and his crew have LVP nearly finished through the ADU and its basement. Kevin calls it a click floater, no adhesive, and Jay demonstrates on a scrap: click, tap, snug. He's not overselling it. That's the install.

The main house gets something else entirely. Kevin and Jay look at a 6-inch flat-sawn white oak, engineered with a plywood backer and a 4-millimeter wear layer. It arrives unfinished, which means it goes down, gets sanded in place, and takes three coats of water-based poly. That's the difference in one sentence: the LVP is a finished surface you click together, and the oak is raw wood you finish on site.

Why that split makes sense: LVP goes where water resistance, durability, and budget carry the most weight, which in this project means the ADU, its basement, and the mudroom traffic path. The engineered oak buys a real wood surface with the dimensional stability of a plywood core, and because it's site-finished, there are no beveled click edges catching light across the floor. It can also be sanded and refinished later, which the vinyl cannot.

What the episode doesn't cover is the unglamorous half of any flooring job. Subfloor flatness, moisture testing on concrete, and the perimeter expansion gap that a floating floor needs are all skipped here, and they're skipped in most TV installs because they eat time and produce nothing photogenic. "Waterproof" on the plank label describes the plank. It does not describe the assembly, the seams, or the slab under it.

MDF Wainscoting in the Mudroom, With Zack and Adrian

A delayed door has jammed up the mudroom schedule, and the painters need to close out their scope, so Zack Dettmore jumps in with Adrian, the carpenter, to get the wainscoting moving regardless. Zack opens with "can I get stuck in here and help you today," which Adrian accepts, and then they draft Dan into the work so he understands what he's living with. This was a tour-heavy episode for Kevin, so the running helper scorecard (our tally of whether the host is useful on site or just narrating) doesn't move this week. Zack, however, is on the tools.

The layout is the teachable part, and Adrian walks it methodically. Start from the rough frame and hold 1 inch: three-quarters for the jamb, a quarter for shim space. Mark where the door casing terminates. Then the bottom rail lands 4 inches above a 5 1/2-inch baseboard, because the baseboard is going to sit in that gap. On the 75-inch panel, mark center, then measure 2 inches on either side of center for the center stile. Transfer every mark around the board so the faces stay consistent.

Everything is MDF. Zack points out that MDF moves about half as much as solid wood, and Adrian likes how it paints, "like glass." In a mudroom and laundry, dimensional stability is not a small thing. Solid wood rails and stiles would be fighting seasonal movement in a room with a washer, a dryer, and a utility sink. Worth flagging as interpretation, not episode content: MDF swells badly if it gets wet, so the baseboard detail and a proper paint film are doing real work here, and the show doesn't get into which MDF or whether the edges get sealed.

The rails and stiles go together with biscuit joints and glue, which Zack notes keeps the joints from opening up over time. Nail gun, chair rail, then sand in place. Adrian cuts the rail at 42 5/8 inches and the panels come together quickly, which is exactly the kind of speed that hides how much layout happened before the first cut.

Two Panels, Twelve Smart Switches, and One Dad Button

In the basement, Sean confirms a 400-amp total service with two 200-amp panels, one for the main house and one for the ADU. That arrangement goes back to the E22 post on the Walpole ADU framing and the 400-amp service for two meters, and Sean explains why the second panel exists: kitchen appliances, the garage, and the condensers would have filled a single one.

Then the smart lighting. This is the most actionable technical segment in the episode, and it's actionable because almost none of it is exotic. The hub is wired like a traditional system and plugs into the router by Ethernet, wherever the router happens to live. The switches talk to it by radio frequency. Sean confirms that smart breakers aren't part of the picture.

The retrofit point is the useful one. A smart switch looks like a paddle switch, takes the same conductors, and adds one requirement: a neutral. Standard switches don't need one, which is the gotcha in older homes, where switch loops sometimes run without a neutral in the box. Sean says these can go into anybody's house as a straight swap, and that's true where the wiring cooperates.

At the front door, a four-gang box holds one traditional switch for the interior lights and three smart ones for porch recessed lights, sconces, and a wireless remote. The wireless unit controls low-voltage landscape lighting on the stair treads, and it's wireless because the transformer lives down in the mechanical space, out of the weather. Dan asked for one button that turns every exterior light on or off at once. Kevin calls it a dad move immediately, and Sean agrees. Total install: 12 smart switches, with two still to go in the basement.

DIY Confidence Scale

Roughly a 6 out of 10 this week, and the split is clean.

The wainscoting is the approachable project. It's patient layout work, careful marking, and a biscuit joiner, and a confident DIYer with a miter saw and a level can absolutely build a mudroom panel. If you're going to try it, spend an hour on layout before you cut anything, because Adrian's whole method is measuring twice and letting the baseboard height drive the bottom rail.

The electrical and the flooring are not DIY work. Adding circuits, sizing a 200-amp panel, and wiring smart switches with a neutral requirement belongs to a licensed electrician, and in many jurisdictions a homeowner pulling permits for that work isn't allowed at all. Site-finished white oak is its own trade. Sanding in place and applying three coats of water-based poly without leaving lap marks, drips, or a visible sheen line is a skill, and floor finishers earn their rate. If you want wood in a basement or a mudroom and you're doing it yourself, buy prefinished.

Additional Resources

• Watch on PBS
• Official This Old House episode page

Season 47's Walpole project has spent the winter in the mechanical, structural, and finishing stages, and the episode's own preview points to moving day next, with a double homecoming for the family in the ranch and the grandparents in the ADU. Wrap episodes compress a long stretch of punch-list work, system commissioning, and cleaning into a short segment, so if next week looks effortless, remember that the last few weeks on a job like this mostly don't photograph well.