Polystyrene coving

[Jupiter01]

I’ve brought a new saw, plastic mitre box and even preformed coving corners to make the job easier. I’ve scoured YouTube for videos on how this is done. What could possibly go wrong!

one problem: none of my comers are 90 degrees!! Are the ever?

unless I’m wrong, none of the above works.

a hammer to crack a nut may be but can I use a angle bevel and the set my makita mitre saw to this angle to chop out the corners from the polystyrene coving?

 

[johnny2007]

Yes, that's what i do all the time.
The mitre saw will cut a very clean edge in the polystyrene.
I usually take a 90 degree perfect cut, offer it to the inevitable ****ed wall and see how much more or less of an angle to cut.
Try that with small pieces and you will see that by the third corner your first guess will be right.

 

[Jupiter01]

Awesome. I was concerned that the makita mls100 may obliterate the lightweight polystyrene coving.

Also, what do you recommend for sticking this on please? I don’t have too much to do. It’s going onto a ceiling with woodchip paper (emulsioned over) and the walls are painted

 

[KenGMac]

How about using lengths of cove, you set the cove in place between wall and ceiling mark a pencil line from wall [A] on the ceiling then place the cove on wall again mark the position of the coves on the ceiling in the two directions.

OK so far??

if you then draw another pencil line from the wall corner, either internal or external to the position that each previously marked lines on the ceiling intersect, you can transfer this intersection point on to the length of cove you are trying to fit. from there use the marked cove to cut an Off 90 degree cut??

Hope this all makes sense?

Ken.

 

[johnny2007]

Coving adhesive.
I like the wickes own brand, but with polystyrene everything works as it is lightweight.
As long as it is solvent free it should work.

 

[johnny2007]

How about using lengths of cove, you set the cove in place between wall and ceiling mark a pencil line from wall [A] on the ceiling then place the cove on wall again mark the position of the coves on the ceiling in the two directions.

OK so far??

if you then draw another pencil line from the wall corner, either internal or external to the position that each previously marked lines on the ceiling intersect, you can transfer this intersection point on to the length of cove you are trying to fit. from there use the marked cove to cut an Off 90 degree cut??

Hope this all makes sense?

Ken.

Unfortunately it doesn't work properly on curved surfaces if the two halves are not cut at the same angle.
Works on skirting though.

 

[sparkwright]

There is a technique to mitre coving - when I tried it back in 1900 and something, I used a mitre box, and ended up with massive holes in the middle of the corners. I was doing it wrong, but I can't describe how - it should have worked bit it just didn't!

 

[johnny2007]

The trick is to keep the coving square to the mitre saw without bending it.
Practice makes it perfect.

 

[Jupiter01]

@KenGMac i read you response last night and again, this morning. I am still struggling to grasp the approach. That’s me and not a reflection of your helpful suggestion!

Can I not use the bevel square to measure the exact angle and then set my makita mitre saw to this angle and cut the coving?

This is the approach I would use with skirting or architrave. Am I overlooking anything?

 

[johnny2007]

It should work but I prefer the empirical approach.
2 bits of coving cut perfectly at 90 degree,
Offer them to the corner and see how much + or - angle to cut,
(Usually it's not more than 2 degrees per cut, unless your walls are really bad),
Cut 2 more scrap bits to the assumed angle (always conservative, can cut more later),
When they fit, use same angle to cut the final coving which you will stick to the wall/ceiling.

 

[Jupiter01]

But if you have a angle bevel, why not grab the exact angle rather than the trial-and-error approach?

 

[johnny2007]

Because you can only get the angle from one point while the coving is at least 90mm.
So if your plaster is curved or indeed angled vertically, you will end up with the above mentioned gap.
Tried and tested many, many, many times.

 

[johnny2007]

I forgot to add that with the chop saw you can cut different angles on 2 different axes.
For example, if you have an internal corner of 88 degrees, you'll cut 44 on each bit of coving but it opens up at the top.
This means that you will need to adjust the vertical angle on the saw to make the 2 pieces meet perfectly.
Cannot do this with manual saw.
However, on many commercial jobs i have cut all at 90 and left the rest to the decorators who would fill the gaps with cove adhesive and finish off with flexible caulk.
Good decorators will make the joint look perfect.

 

[opps]

However, on many commercial jobs i have cut all at 90 and left the rest to the decorators who would fill the gaps with cove adhesive and finish off with flexible caulk.
Good decorators will make the joint look perfect.

As a decorator, I groan when presented with coving that has external corners that meet at the bottom but not at the top. Yes, I can sort it out but given that I am filling a void, I need to fill, sand, fill a bit more, sand a bit more, fill a bit more, etc.

Sorry, not having a dig at you but sometimes the trades before me do not appreciate how long it will take me to rectify things that they should have done properly in the first place. I am at the end of the proverbial chain. I totally get the whole "the decorator will sort it out" mentality but as a self employed decorator, I tend to be the one that ends up out of pocket. I quote a job and then discover that the chippy didn't bother sanding the door edges after planing it or that he he has a chip in the planer blade that is only evident after I have applied the first coat of primer and that I then need to belt sand the door edge. Or the plasterer who has bucket loads of dimples in the finish that need filling and sanding, the electricians who don't know how to was their hands before pushing the light fittings up. The tilers who slop specks of adhesive all over the walls. The list goes on.

We are the people that can make or break a job. By that I mean that a cruddy decorator will make the best job look pants. Show us some luv...

 

[johnny2007]

I have a lot of respect for you decorators.
I try to keep the joints as perfect as possible and in my primary trade (chippy) i was always complimented by the decorators about the neat joints and good jobs in general.
Then came this 5000 homes pledge aka 5000 badly built dormitories and we were given 15 minutes to fit every door and frame.
Clearly they would be all over the place but the bosses preferred speed to quality work.
Also they started giving us extra stuff to do, for example coving which had to be done at the speed of light.
So, unfortunately today's commercial built are a mess not to last and the decorators have the hardest job of all to make very poor accomodation look decent so they can be sold to unscrupulous investors or desperate working class souls.