Ask This Old House S24E18: New Orleans Spanish Cedar Shutters, Fertilizer Labels Decoded, and Hardwired Smoke/CO Alarms That Talk to Each Other

Season 24, episode 18 sends the show to three places that share almost nothing except a rulebook. Nathan Gilbert is in the Bywater neighborhood of New Orleans, where the Historic District Landmarks Commission gets a say in what a shutter is made of and how many hinges it carries. Jenn Nawada and Lee Gilliam stand around fertilizer bags with Kevin O'Connor. Heath Eastman rewires smoke detection with a local fire chief standing in the hallway.

The through-line: none of these jobs begins with a tool. Each one begins with a permit, a label, or a code requirement, and the work is mostly about getting those decisions right before anything gets cut.

Bywater Shutters: Permit Rules, Spanish Cedar, and Two Hinges Instead of Three

Homeowners Lenna and Emily have lived in the neighborhood about a decade and owned their side hall cottage for four. The shutters on the front are soft and rotting, which matters more than cosmetics in a city where closing shutters before a storm is a normal part of the year. You cannot close a shutter that has gone spongy around its hinges.

Nathan calls in Scot, a local carpenter who has been through the permitting process before. In a historic district, the commission reviews the application and approves or denies it, and the guidelines reach down to wood species, hinge style, hinge location, and paint color. The goal is not restoration to a museum state; Scot describes it as keeping what was there originally, just fresher. The new shutters are Spanish cedar, which he calls well suited to the New Orleans climate and its elements. Hardware is a cast-iron replica set: hinges, a slide bolt, and catch latches matching antique historic shutters.

One deliberate change: going from three hinges per shutter to two, top and bottom. The city approved it because the rest of the neighborhood reads that way, and it also makes the shutters easier to lift off the pins when a storm is coming. Nathan had to loosen the middle hinge screws on the originals to swing the shutter out and off, which is exactly the annoyance the new arrangement avoids.

Fitting the Shutters: Dutchman Patch, Plane, Prime, Hang

The old middle-hinge mortises get Dutchman patches, which is carpentry-speak for gluing in a matching piece of wood to fill a void so the surface is whole again. Then the shutters are measured and cut at the bottom to fit the openings; the transcript captures a measurement of 34 9/16 at the bottom. Scot planes the edges at a slight angle so the shutters pull tight against the window when closed.

Here is the part a homeowner will get wrong on the first try: the fit is cut in the closed position, not the open position. Nathan stresses keeping track of orientation and using reference marks. Shutters look symmetrical and are not, especially once you have planed one edge and cut the bottom of one leaf.

New hinge mortises get cut, and every freshly exposed edge on both the shutters and the window gets primer before assembly. That is the durability step. Cut end grain wicks water, and in a humid coastal climate an unprimed end grain is where the next round of rot starts. Hinges are marked, pre-drilled, and screwed in, then the slide bolt and catches go on. The shutters swing open, the hardware works, and the homeowners get leftover homework: touch-up paint on the cut edges and on any nicks from installation.

What the segment does not show is the permit paperwork, the disposal of the rotten originals, or the number of times two people carry a shutter back to the bench. On television the job looks like an afternoon. It is a long afternoon, and the hinge work alone involves more test-fitting than airtime allows.

Fertilizer Without the Guesswork: NPK, Organic vs. Synthetic, and the Case Against More

Kevin walks in on Jenn and Lee mid-argument about organic versus synthetic and asks them to back up to the basics. Jenn recalls Roger's framing of right plant, right place, right fertilizer, which still holds: you need to know your plants, your soil, and your existing lawn before the bag matters at all.

Lee walks through the three numbers on the label. Nitrogen drives top growth and lawn color, so a higher first number is the green-up number. Phosphorus, the middle one, supports roots and contributes to blooms and fruit. Potassium, the last number, handles overall plant strength and structure. Jenn mentions superphosphate when blooms stall, and hitting potassium when roots need attention.

Organic products come from compost, manure, and bone meal, plus pelletized materials. Lee points to Milorganite, which he describes as derived from human waste, and Kevin works through the obvious comparison to manure. The important difference is timing: organics break down slowly through earthworms and soil microbes, feeding soil health over the long haul. Synthetics act fast and hard. Jenn's analogy is a sick plant and an antibiotic, meaning quick-acting treatment rather than routine diet.

Mixing is allowed and both of them do it, particularly pairing a synthetic with a pelletized organic on a lawn. The warning that deserves repeating is about quantity. Over-application can burn a plant, and heavy rain can leach excess nutrients into watersheds where they feed algae blooms. Follow the ratio printed on the bag and know the local regulations. Lee notes that this is why you have to be aware of where you live before you spread anything.

Lee was last on the show walking through grass seed selection in S24E16, and this segment is the logical next chapter: what you feed the lawn once it is up.

Hardwired Alarms That Talk to Each Other

Tracy wrote in about smoke detectors, and Heath brings Chief Stephen along to set the placement rules. Heath's opening narration supplies the stakes: a small flame can become a full-blown fire in under 2.5 minutes, and house fires cause more than $10 billion in damage annually.

Tracy's history explains a lot of households. She had a monitored household fire warning system, moved to battery-operated detectors, and lost two things in the process: central notification and interconnection. If a battery detector in a basement sounds at night, the second floor may never hear it, especially with an air conditioner or fan running. Chief Stephen calls interconnected smoke and carbon monoxide alarms the best system in all instances.

On detector type, the chief states that new construction and remodels now use photoelectric detectors only. Ionization units were previously allowed but could not sit within 20 feet of a kitchen or a bathroom with a shower, and they triggered false alarms frequently from steam. The chosen units combine photoelectric smoke detection with carbon monoxide detection and announce the event by voice and tone, so an occupant knows whether to expect fire or CO.

Placement is the segment's real content. One detector per bedroom, ideally 3 to 5 feet from the door. The hallway detector should sit within 10 feet of bedroom doors, but 3 to 5 feet down the hall from the bathroom and kitchen rather than right outside them. Keep units away from ceiling fans and away from HVAC vents, both for dust loading and because air movement can delay activation. Base of the stairs, on the ceiling of the landing, never inside the stairwell. An attached garage gets a heat detector centered on its ceiling. The chief's closing advice is the practical part: call your local fire department. They will tell you what to buy and where it belongs.

Installation and What the Edit Leaves Out

Heath compares three generations of hardware: battery-only detectors, hardwired units with a replaceable backup battery, and hardwired units with a 10-year sealed battery. The sealed-battery version still has a service life, and the manufacture date printed on the back is how you check it without relying on memory. It should chirp at end of life, but the date is the honest answer.

The wiring is straightforward in principle and slow in practice. He cuts round old-work boxes with a 3 3/4-inch hole saw fitted with a dust collection bowl, runs 14/3 NM cable, and makes connections color to color: black to black, white to white, red to red, grounds together. The red conductor is the interconnect, continuous through the loop, which is why the first box has one cable and the subsequent boxes have two. If a segment on conductor color logic sounds familiar, Heath built a three-way switch to demonstrate the same discipline in S24E14. Red traveler there, red interconnect here. Same idea: the wire has a job, and guessing at it is how systems fail.

Fishing the walls is the part that consumes the day. Heath drills from the wall cavity into the attic, threads 5-foot fiberglass fish tape sections together to run an 8-foot wall, wiggles the tape through the top plate, tapes the cable on, and pulls from above. Before cutting, he probes with a pre-bent tie wire through the hole saw opening to confirm there are no obstructions. Once he has attic access, he cuts and installs all the boxes first, then staples and pushes wires through from above. That decision saves time and it is a reminder that access, not skill, usually determines how a job like this goes.

The test cycle is loud and voice-announced, and Tracy keeps hearing protection on for it. That is the point of the whole segment.

DIY Confidence Scale

Reading a fertilizer label: 1 of 10. The NPK numbers, the ratio on the bag, and the organic-versus-synthetic tradeoff are all learnable in one sitting. Understanding local regulations is the only step that requires homework, and it is a phone call or a website.

New Orleans shutter replacement: 7 of 10 for a competent carpenter, higher for a first-timer. The mortising, Dutchman repairs, and fitting shutters in the closed position are all skills built over years. The historic-district permitting adds a layer that has nothing to do with woodworking.

Hardwired interconnected smoke and CO alarms: The placement rules are a 2. Reading the manufacture date on the back of a detector is a 1. Running 14/3 through finished walls and an attic is electrician territory. If you cannot trace a clear cable path, hire the work and ask the fire department about placement before anyone cuts drywall.

Additional Resources

• Watch on PBS
• Official This Old House episode page

Two of the three jobs this week come down to a decision made before anyone picks up a tool. Worth a walk through your own hallway this weekend: how old are the detectors, and can you hear the one in the basement from your bedroom?