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How to attach new cornice with existing corners?

One side done!Hello all,

<< Firstly, this is an update, I managed to use the left side as a template to cut against, photo doesn't do it justice but I think it's a nice fix, just a template at this stage but I will transfer to the final piece. >> Photo attached

I am trying to attach some new cornice to my study ceiling wall. Its 65mm cove cornice, horsehair plaster. I have had some new stuff made up here in Canberra, 65mm with fibreglass or something, so dimensions are all the same. I took care when removing old cornice but it was on there tight! I have a mitre box and understand how they work now, 65mm up the side wall and 65mm width on the bottom, I made some spacers to make it work. Anyhow, I think the angle is more like 50 degrees maybe because I cut it that way and it was way off. I tried to make a 50 degree cut in the mitre box and did a test cut, it's just not right! For something so seemingly simply I have always put off cornice, before I fork out I thought I'd try for this 2.7m piece myself!!

My question is, how do I work out with the "angle" is of the current remaining corners, I used a sliding bevel on the old piece and it came out at 50 degrees, I still have the old piece for the left side, either way it doesn't seem to help me! I have a coping saw, I got closer but still off. Anyone got any ideas please for how to "scribe" or something so I can get this new piece up! This is my last bit of renovation I am doing on this house, I just added insulation to the final wall! That's all done and dusted, sheets back up but this cornice!! Thanks,

Geoff

left Left right Right Length Length

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MitchellMc

Great job @geoff_70. Neat trick using the template.

Just so you know, cornice is typically not that neatly joined. It just needs to be reasonably close, and then Spakfilla is used to fill the gap between them. There's normally a bit of a gap unless you can get the angle perfect. A specific cornice mitre box like the Intex Cornice PlasterX® Plastic Dual Mitre Box (55/90/135°, 55/75/90mm) makes life easier, but as yours is 65mm, it likely would still take some trial and error.

Have you managed to do the other cut now, or are you still looking for a method to scribe the final cut? Typically, I'll cut the angle oversized, offer up the new piece and check my angle. I then make small adjustments to the angle until it fits just right.

Please let me know if you have any questions.

Mitchell

geoff_70

Hello Mitchell,

Thanks for the great reply! I got that nice cut/join on the left by accident//luck, I was not aiming for anything, I had the old piece and simply held it and cut along it, it worked! The right hand side is being somewhat tricky but I reckon with your advice I will get this cut tomorrow, I had a few goes tonight but I am going slow, then of course I will need to transfer to the real piece which will be nerve wracking at $65 a pop (I only have 1!!)

Thanks,

Geoff

geoff_70

OK I have managed to cut the angle more or less ok for the right corner. I think with a bit of cornice cement jammed in there will suffice surely? All I need to do now is transfer these to the real piece and put it up! I am hoping if I go slow this will work!

MitchellMc

That's looking good, @geoff_70. Add a bit of Spakfilla and sand, and you'll be good to go.

Mitchell

geoff_70

Thanks Mitchell, so do I use spakfilla or cornice cement?

MitchellMc

Cornice cement is a more specific product for that usage, so probably better to stick with it, @geoff_70.

Mitchell

geoff_70

Hello all, Been awhile! I finished this cornice back in June I think. I ordered an Exact match here in Canberra and cut to size etc. This can be done! I only replaced a single bit but I reckon (lol) I could do a whole (small) room but it would be tricky! I used cornice cement, just the DIY stuff, used a small spatula to fill in the gaps and corners, smoothed it all over with a cloth/sponge and gave it a sand a few days later. Looks fantastic and has been painted fully only a few weeks ago! Just thought I'd post for other people to see it can be done! Length is 2.7m, was good to have to the old bits so I would advise to at least keep the corners to try and match them up. I used a Japanese saw to cut the angles, sort of a 45 degree tilt, anyhow! Cheers!Completed pieceRighht hand corner

JacobZ

Hi @geoff_70,

I have only done a little bit of cornice in my life, and there is a bit of an art to it. For a first attempt, you have done a magnificent job, and now that it has been painted, it looks like it has always been there.

Thanks for the update.

Jacob

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