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Measuring for mouldings - laser measurer accurate enough?

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Measuring for mouldings - laser measurer accurate enough?

I'm going to be installing many feet (ordered over 200') of crown moulding. Just wondering if a laser measurer is accurate enough? Or if not accurate, better than a tape measure over the span?

Looking at a Bosch GLM30 for $60.
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Lasers are generally accurate enough for this kind of measuring (ie room dimensions), the one you linked appears to be accurate to 1/16th so that should be good enough. Generally I use stabila lasers and they do a good job for what I use them for.

That said, whats your plan for joints? If you're doing mitres you're probably fine with this approach, however if you do coping you may end up using your tape in the end. Idk if the laser will be able to shoot the top of your crown so you know what length to cut the coped piece too.

I have lasers and will usually use a tape for all my "final" measurements. If you're going to do all your measurements solo, then maybe you need the laser to start off with, and then switch to tape for smaller runs. Again, this depends on if you're coping or using mitres.
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I was planning to mitre joint. Not sure if I have the skills to cope joint such a complex (to me) profile and given that it is a crown too. We're using the same moulding that was already installed (upside down?) and it is a bit complex. UL MDF for what it's worth.

I think there are only 3 or 4 runs where I can tape measure by myself. One run will require the whole 16' piece and then some.
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An amateur tip that doesn't require accurate measuring at all:

Cut it long, check the fit on the wall, then shave off what you need. It'll take longer but there's less chance of screwing up.
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FWIW, what is the order of doing things?

Cut to fit
Paint
glue & brad nail
caulk corners,
paint and touch up as necessary
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RCGA wrote: An amateur tip that doesn't require accurate measuring at all:

Cut it long, check the fit on the wall, then shave off what you need. It'll take longer but there's less chance of screwing up.
I pretty much do this already.
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thriftshopper wrote: I was planning to mitre joint. Not sure if I have the skills to cope joint such a complex (to me) profile and given that it is a crown too. We're using the same moulding that was already installed (upside down?) and it is a bit complex. UL MDF for what it's worth.

I think there are only 3 or 4 runs where I can tape measure by myself. One run will require the whole 16' piece and then some.
Coping isn't as hard as people thing, just takes a bit more time. Also, if you screw up you can just cut off a bit more and start again, its not like you will have wasted pieces.

If you do choose to go mitres, get an angle gauge, something like this: https://www.atlas-machinery.com/l-s-starrett/505p-7/ I'm sure most hardware stores will sell something like it. It will help you a lot in getting tighter mitres and avoid you having to do emergency surgery and filling up gaps.

If possible I would recommend getting a 2nd pair of hands for some critical points.
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thriftshopper wrote: FWIW, what is the order of doing things?

Cut to fit
Paint
glue & brad nail
caulk corners,
paint and touch up as necessary
Generally I think you have the idea. Depending on the size of your molding, you're not going to have joists on 50% off your walls to nail into, so you need to think about some backing/blocking for something soil to nail into.

If you're looking for some videos to watch to get a better idea, I would recommend this guy: https://www.youtube.com/channel/UCYU9ct ... gNPfEzL6dg
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Cut a pair of 6” -12” pcs inside corner and outside corner to check and find angles. If you cut them at a known angle, you can kind of figure what cuts you need to make.
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Do I need the gauge if I have an adjustable a mitre saw? Have a Hitachi and a Rona brand (double compounding). The Rona has the finer blade but I can move them.

There's only 2 (outside) angles that are not right angle (should be 135 degrees), but I guess I shouldn't count on the supposed right angles being right angles especially with big moulding pieces.



Totally forgot about no joists to use where they run parallel. Unfortunately the attic has been filled with ~2' of fiberglass. Will glue hold the pieces in place?



Thanks for the tip. So use the short scraps for such?
Last edited by thriftshopper on May 21st, 2020 6:15 pm, edited 1 time in total.
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So one thing about trim work, is that your corners will never be perfect 90s, or 135s or whatever. They will always be a few degrees off. This is where the angle finder helps, so you know to cut to 46.5 degrees right off the bat.

Alternatively, if you're not doing too many corners, you can just install your first piece, and then on your second piece just do it by trail and error. Cut it 45, test fit it, and if its too open or closed, just adjust the angle till you have something that works.

Generally for places where you have no joists, what I usually do is put some blocking or longer strips ripped at 45 behind. I sink them into the top plate so its nice and sturdy, then nail into that. Always leave yourself a bit of space between the blocking and the crown so it never pushes the crown out. Alternatively, I know depending on the size of trim, or just regardless, a lot of people will just double nail at opposite 45 degrees into the ceiling if there is no joist. Ie, put in 2 nails, which will be at 90 degrees to each other, and both angled at about 45 degrees to the vertical.
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SubjectivelyObjective wrote: 're looking for some videos to watch to get a better idea, I would recommend this guy: https://www.youtube.com/channel/UCYU9ct ... gNPfEzL6dg
Just spent an hour+ watching that video. The person uses a battery-powered angle grinder with 80 grit sander to cope the moulding. Says MDF is too brittle for cope sawing. I have a corded one one speed. I imagine it would not be a good idea for the profile?

Annotation 2020-05-21 174653.jpg


Moulding is what is in most of the main level of the house already. Fussier than what I'd like personally, and it was installed upside down from the picture to boot.
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SubjectivelyObjective wrote: So one thing about trim work, is that your corners will never be perfect 90s, or 135s or whatever. They will always be a few degrees off. This is where the angle finder helps, so you know to cut to 46.5 degrees right off the bat.
Got myself a "cheap" Sterrett. The made-in-China one was 1/3 the price of the made-in-U.S.A. one (same brand, different colour, U.S.-made one a bit heavier.
Generally for places where you have no joists, what I usually do is put some blocking or longer strips ripped at 45 behind. I sink them into the top plate so its nice and sturdy, then nail into that. Always leave yourself a bit of space between the blocking and the crown so it never pushes the crown out.
1"x3", 2"x2"s, 2x3"? What does one use?

Delivery has been pushed back a week because the lumber shop or its supplier screwed up so I don't have a physical piece to look at.
Alternatively, I know depending on the size of trim, or just regardless, a lot of people will just double nail at opposite 45 degrees into the ceiling if there is no joist. Ie, put in 2 nails, which will be at 90 degrees to each other, and both angled at about 45 degrees to the vertical.
That is what was suggested in the video above.
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SubjectivelyObjective wrote:
If you're looking for some videos to watch to get a better idea, I would recommend this guy: https://www.youtube.com/channel/UCYU9ct ... gNPfEzL6dg
This guy has fantastic videos, you can really go down a rabbit hole when you start watching them he has so many useful ones.

I second coping with an angle grinder with a flapper wheel. It chews through mdf like butter and I get MUCH nicer, smoother edges then i do with a coping saw.

I just got a all time low pride notification from 3camel for that angle finder on amazon.ca as well.
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Alternatively, I use a Dremel with a cut-off wheel and sanding drum bit for tight tight joints.
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LOOSEWHEEL wrote: Alternatively, I use a Dremel with a cut-off wheel and sanding drum bit for tight tight joints.
Thanks. I have one so might as well put it to good use.
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I would say that a laser measure is NOT accurate enough to measure long moulding pieces. Regardless of the accuracy specs, they are subject to some jitter and slight miscalibration errors. But you should experiment: take a bunch of sample measurements, see how repeatable they are, then compare to a physical tape measure. If you can establish repeatability, and calibrate the accuracy compared to the tape measure, then you may be able to use the laser measure. But if you use the same tape measure to measure both the room and the moulding, then you are guaranteed to be accurate.

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