How are floor joists normally dealt with when putting in can lighting?

September 13, 2022 1:29 PM

We asked electricians to put in can lighting. They suggested we put in wafer lights instead because they're easier to install. After reading up on wafer lights, we decided we didn't want them and still want can lights. The electricians mentioned that can lights were tricky because if they find a floor joist where a can is supposed to go, they have to put it elsewhere. But wafer lights are a new thing, so people must have had to deal with the floor joist issue before. How did they do so?

The electricians seemed hesitant to go forward, giving caveats about how there may be gaps after their cuts, etc. Searching tells me that it is indeed hard to find floor joists without actually cutting into ceilings, so maybe installers used to just cut probe holes all the time, and modern electricians just don't want to do that anymore.

posted by ignignokt to Home & Garden (18 answers total)

Stud sensors and common joist spacing can help identify where they are. The challenge with traditional can lights is working within those constraints while still putting in lights with appropriate spacing that works for the space
posted by walkinginsunshine at 1:41 PM on September 13, 2022 [3 favorites]

There are electronic stud finders and floor joists have a distance between them, like maybe16 inches, I know that is the spacing for wall joists. You have to want your can lights between joists. Cutting joists is bad for structural integrity. You might need to employ a carpenter to determine spacing and then use electeicians for wiring them in place. Then a finish carpenter or interior person would finish around the can lights after.
posted by Oyéah at 1:42 PM on September 13, 2022 [1 favorite]

You just have to work out the spacing of them, so you don't put one where a stud is, which will kill your look and drive you batty. Get a good stud finder and you can draw them out yourself and tell them exactly where to put them.
posted by The_Vegetables at 1:52 PM on September 13, 2022

Best answer: I spent a day and a half crawling around in my attic installing cans for my bedroom. It was a giant pain in the ass. The cans have to go between the joists and though they have adjustable brackets, they need to be a couple of inches away form the joists. So if you're installing multiple cans, getting them evenly spaced on the ceiling is really, really tricky.

If I were to do it all over again, I'd use flush mounts or wafers or anything but cans. I used what was basically the first gen of LED cans though so they've probably improved somewhat.

I was fortunate to have access from above so I could tell where the joists were. Punching through drywall when you don't exactly know where the joists are will result in a lot of false starts and holes where you don't want them to be.

In my experience stud sensors are almost useless, even more so on a ceiling because there is often strapping between the joists and the drywall that runs perpendicular to the joists. Insulation, older structures, and other factors also throw off stud sensors.

That said, a good electrician should have a few tricks up their sleeves to find the joists. It's going to take them longer to do this though, and they're going to punch a few extra holes, so if you have a price budgeted for this job (and they agreed to it) I don't blame them for not wanting to put in the extra work unless they up their fee.
posted by bondcliff at 1:53 PM on September 13, 2022 [10 favorites]

The difficulty is in locating the joists. Depending on the age of your house and/or the work done by the framers, this may be a tricky proposition. If it is a modern ceiling of drywall on standard joists spaced at 16 or 24 inches on center, all they have to do is find one joist.
posted by slkinsey at 1:54 PM on September 13, 2022

The best stud finder in the world won't tell you there is a hvac duct, drain pipe or some sort of cross blocking a couple inches above the gyproc. Cans are a pain in the ass to retro install and easily 30% of the time you end up either changing the pattern or cutting a big hole to change existing infrastructure when you are installing in a floor space once you find out what is in there. Keep in mind that not being able to place even a single recessed fixture means changing all of them.

Lights need to be evenly and symmetrically spaced and require several inches on each side of the centre line. Doing that in a space designed for surface lighting can be difficult to impossible.

Also if the space is insulated, even just for sound, you need bulky insulation contact cans which make things worse. And you can't easily see what is in the space.
posted by Mitheral at 2:37 PM on September 13, 2022 [3 favorites]

Drill a small hole in the ceiling. Bend a piece of coat hanger wire at a right angle. The bent piece should be as long as the radius of the can. Insert the wire into the drilled hole. Rotate the wire. If you can swing it all the way around, there is enough clearance for the can.
Oops, wrong place? A tiny dab of spackle will cover the hole.
posted by H21 at 2:50 PM on September 13, 2022 [1 favorite]

Response by poster: While I appreciate the tips, I'd like to focus on this aspect of the question:

But wafer lights are a new thing, so people must have had to deal with the floor joist issue before. How did they do so?

A fine answer would be "generally people didn't install can lights after the place was built" if that's the truth!
posted by ignignokt at 3:51 PM on September 13, 2022

They would move the location of can lights. You can't cut structural members.

A wafer light is shallow enough to not impinge on the structure
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posted by nickggully at 3:57 PM on September 13, 2022 [2 favorites]

A fine answer would be "generally people didn't install can lights after the place was built"

There are differences in can fixtures for new construction vs. renovation. Generally the reno ones are designed to sit on top of the ceiling drywall rather than be bracketed to the joists. You still have the issue of spacing them between the joists however. They dealt with it by doing what your electrician doesn't want to do, and that is spending a lot of time figuring out where the joists are located and designing the layout of the lights based on that. It's a lot of work, and generally isn't as simple as some might have you believe. While I've never hired an electrician to install lights in a renovation, I'd guess that installing multiple cans in a room are usually done during a major reno, when the ceiling would likely be replaced anyway.

How much looking around have you done? There are many, many options for LED fixtures, including low voltage ones that would be a lot easier to install.
posted by bondcliff at 4:36 PM on September 13, 2022 [3 favorites]

Best answer: Yup, sometimes installing can lights in a renovation, you cut a hole in the ceiling, find a joist, and have to make a new hole somewhere else.

We did a renovation where we placed can lights and had to adjust the placement because our original location had a joist in the way. It was fine! But this was a big renovation so we had painters and plasterers in anyway, they could make as many holes in the ceiling as they wanted and patch them and it was no problem. If you are planning on hiring *just* an electrician, they probably aren't planning on patching your ceiling, and they may be reluctant to leave you with extra ceiling holes (though usually you end up with at least some extra holes to fish wires through, etc...) especially since you might have to adjust other lights that don't conflict with joists to get a symmetrical arrangement.

I wonder if there are particular symmetry/placement issues the electricians are worried about? For instance, we have a room where the lights are aligned with the windows and if we had to do them slightly offset from the window centerlines it would look pretty noticeably bad.

That said, if exact placement isn't an issue and if you are comfortable patching ceiling holes or hiring someone to patch ceiling holes, just tell the electrician it's OK if they find a joist, you can just cut new holes. If your electrician won't do it, you can find one who will!
posted by goingonit at 6:57 PM on September 13, 2022 [2 favorites]

Best answer: A fine answer would be "generally people didn't install can lights after the place was built" if that's the truth!

It sort of was. Recessed lighting really had a surge in popularity in the 80s but renovation installation would command a premium especially since there was less variety and the housings were much more sturdily built. I can retro a surface light on a ceiling octagon in less than 15 minutes in most cases for simple fixtures. A single recessed can is going to run at least double that (but who installs a single recessed fixture?). Doing say a recroom with half a dozen general lighting cans plus a couple wall washers or accent lights is going to take you all day even if everything goes right and could take a couple days if things don't. That is a lot of money in labour and most homeowners are cheap. And at a certain point it is actually cheaper to just pull the gyproc down to install the lighting. I've done exactly that in a few kitchens where the ceiling area to number of lights ratio justified it.

I don't think it would be an exaggeration to say that a large percentage of can retrofits historically and currently are done by homeowners or handymen rather than electricians because of the cost factor. Few people are willing to insist on the features that a can can provide verses a puck light in a retrofit situation once they find out how much it will cost.

Of course I've also installed fixtures in homes that cost 10K-40K dollars so there are also definitely people who will pay. It's not too bad of a week when you get to spend it laying on your back on scaffolding installing a fixture.

PS: LED wafer lights are fairly (10-15 years) new but pucks have been around for at least 40 years mostly in halogen form. Mostly used for under cabinet lighting but some are/were available with somewhat attractive trims and I've seen them in spaces like hallways or bathrooms where there wasn't a lot of installation space above the ceiling. The drivers would be remote mounted so the actual fixture didn't require as much room.
posted by Mitheral at 8:33 PM on September 13, 2022 [2 favorites]

I never thought I'd be the one to warn on a thread but PLEASE if you follow H21's approach, find some way of insulating yourself - I've worked on a ton of buildings and exposed live wires is common ime.
posted by unearthed at 10:01 PM on September 13, 2022 [1 favorite]

The other option for retrofitting canned lighting was to use drop ceilings. That's where you just bring the ceiling down the height of the lighting. This is another fast and easy (so cheap) method to get all your lights lined up without needing to work around joists. This comes at the expense of room height, which most residential spaced don't have in abundance. My house certainly didn't, which is why the best part is that they are super easy for someone rando like me to tear out.

The electrician is steering you towards the better solution - I have exposed joints on one floor and I'm still going to install 'wafer' style lights. Originally I was going to use cans, and it would be very straight forward to do so. But cans were only necessary to house old fashioned bulb lights, and I have warmed to how some of the wafer lights can be styled, and there is many choices.
posted by zenon at 7:16 AM on September 14, 2022 [1 favorite]

Response by poster: OK, I think I now have a sense for how things used to be done, pre-wafer lights. Anyone in the future looking at this question for the answers to that can stop here.

There does, however, seem to be an appetite for talking about the value of wafer lights, so we can steer to that now, if the mods are cool with that.

Are there wafer lights that are replaceable without having to do wiring? Because that is our main concern.

How much looking around have you done? There are many, many options for LED fixtures, including low voltage ones that would be a lot easier to install.

I've looked quite a bit, and the one thing I can't seem to get around is that all wafer lights seem to be impossible to replace without having to do wiring. We want the electrician to do the wiring, and we don't want to have to call the electrician when we want to change a light.

I do see wafer lights that have a junction box and a modular connection between that and the light module. When I see that, I think, oh maybe you can change those lights by leaving the junction box alone and plugging in a new light module. But the manuals I can find for these seem to imply that there is significant operational stuff inside the junction box, so we're back to taking it all out and rewiring.
posted by ignignokt at 1:03 PM on September 14, 2022

Usually the high voltage goes to the junction box and from there it's low voltage to the lights, so you could replace them yourself in that case. The trouble is, if one of them burns out in five years, will they still make the same lights and will the low voltage plugs be compatible? I don't have an answer for that. You could always buy a couple extra lights and keep them on hand. While I have had a lot of LED bulbs go bad on me, the fixtures I installed ten or so years ago are still going strong, as are some I put in my basement two years ago. It's very possible you'll never need to replace a light.
posted by bondcliff at 4:17 PM on September 14, 2022

Yeah the LEDs are often rated to 50 years, but how long have they been around so who really knows? The problem is that it’s entirely possible for the power supply to go before the LED itself so even if you could replace the LED there’s still no guarantee you’d be able to fix a dead fixture.

The good news is that replacing these from the power supply on should be a really really really easy job. It’s just connected to mains power with wire nuts and not affixed to the ceiling at all so you pop out the fixture, disconnect the power supply, and pop in the new one. Technically this calls for an electrician but I promise you have the skills to do it yourself.
posted by goingonit at 4:24 PM on September 14, 2022

I think you are thinking that cutting a few extra holes in walls is a bigger deal than it is. I had can lights installed in a reno, and they just cut some extra holes and a 2nd drywall crew came and fixed them up. They also used a few that don't need to be attached to joists, but I'd not recommend those.

Some crews are more interested in some jobs than others, some have different skills, and that is true across all construction trades. I have installed some too myself, replacing some florescent lights. It's not that difficult a job.
posted by The_Vegetables at 2:23 PM on September 15, 2022