Cutting oiled plywood

[unionworkeruk]

I am lining a ceiling with birch ply that I have stained and sealed with matt finish hard wax oil
The sheets ,which are full size, need to be cut to fit so what is the best way of cutting the 4mm sheets without damaging them or the wax/oil finish.
In case anyone asks I cannot water stain the sheets after fitting as I needed to mix different oil waxes to get the finish I want This would be impossible working on a ceiling as I need to sponge as well as roll them. Any advice ?

 

[big-all]

best option is to face with say 6mm ply when cutting so you wont get breakout on the front face
do you have a circular saw?
how are you fixing the ply into the ceiling ??

 

[unionworkeruk]

I will be fixing them to the joists through the existing plasterboard.
A carpenter mate will be helping fix then I want to make sure he does it in the best way to protect the finish. I can make sure we have some 6mm ply and he uses the saw you suggest. Thanks

 

[big-all]

are you fixing through the face off the boards or by sealant or glue on the back ??

 

[unionworkeruk]

Screws through the face of the board

 

[big-all]

not sure how that will work with 4mm boards
a screw head will need about 2mm
you are worried about splintering but are happy with screw in the face so a bit confused as you want a clean clinical face ??

 

[JohnD]

You can blend in the colour of the screws.

I looked at phosphor-bronze boat screws, but you could spray the heads of a box of screws with a dark bronze car paint.

 

[unionworkeruk]

Its going to be a grey ceiling so I am using black headed screws. I have used similar boards on walls without any problems but,yes, it might be an idea to glue the boards to the battens as well because of the weight.

 

[justbigboned]

A decent track saw will minimise tear out on the top. The finish would be mostly unaffected although if you've sealed the edges you'll need to redo. Support spacing is going to be critical for the fixing as 4mm is very thin and is likely to sag over time. I doubt the spacing between existing joists would be close enough to prevent this. I'd be tempted to use a sort of lattice work behind the boards if possible to give the face board some support.

As always, it depends on the finish you're wanting to achieve.

Be aware that ply is not immune to movement. It will bow, cup and twist. A latticework will help control that, but the method of fixing is critical, particularly with gravity working against you and such thin board.

Acclimitise it for a good while, several months ideally in the room you wish to use it in. Use as small sections as you can get away with for your project. Oh and, if not obvious, store flat, not on end! (you'd be amazed how many people store ply propped against a wall!)

Once you've fixed the latticework/support batons, make sure you seal the rear of the panel itself, around the batons, not including them. Be sure not to use wax oil on anything you want to apply glue to!

This will help to stop the board cupping as it dries over time. If you only finish one face, moisture will be lost only through the unfinished face, causing movement.

 

[unionworkeruk]

Thanks for all the info. I have laid the boards flat for over a month now and they are stained and oiled in one side. What do you suggest for the reverse? Is there anything I can use that wont reduce the effectiveness of glue as I need to do as much as possible before I am joined by the carpenter. (I am a painter).

The joists are about 30cm apart and we have another 9m of 2 x 1 so I think the carpenter is thinking of some sort of lattice work. I will check. Also make sure he uses glue as well as screws.

I am using 4mm ply because I thought it would be better being light..

 

[justbigboned]

Thanks for all the info. I have laid the boards flat for over a month now and they are stained and oiled in one side. What do you suggest for the reverse? Is there anything I can use that wont reduce the effectiveness of glue as I need to do as much as possible before I am joined by the carpenter. (I am a painter).

The joists are about 30cm apart and we have another 9m of 2 x 1 so I think the carpenter is thinking of some sort of lattice work. I will check. Also make sure he uses glue as well as screws.

I am using 4mm ply because I thought it would be better being light..

The glue relies on penetrating the surface so not really. If you could get an idea of the support work the carpenter intends to use, then do the areas around where it will be fixed perhaps? The weight is low, so screws would be enough if theres plenty of them. You could always fill the holes but you havent got a lot of thickness to work with so choice of screw will be important too.

 

[unionworkeruk]

I want to use black japanned round headed screws so no issue about hiding or disguising them.
I will find out how he will do the support work but what do you reckon I should use on the reverse? thanks

 

[justbigboned]

I want to use black japanned round headed screws so no issue about hiding or disguising them.
I will find out how he will do the support work but what do you reckon I should use on the reverse? thanks

A couple of coats of waxoil around where the batoning/latticework is I think.

 

[unionworkeruk]

OK. Thanks a lot for all your help.