Fixing 8x4 plaster slabs to wall

mayoman1973

Going to dab and slab kingspan onto the inside walls and then mechanically fix plaster board slabs over this. How many screw fixes do you need roughly per 8x4 sheet? Would 6 suffice?

Maudi

mayoman1973 wrote: »

Going to dab and slab kingspan onto the inside walls and then mechanically fix plaster board slabs over this. How many screw fixes do you need roughly per 8x4 sheet? Would 6 suffice?

Why kingspan at all.why not just blob the 75mil slabs..anyhoo nine mushrooms per board.three top.middle and bottom.

yop

Just get the insulated slabs! I have 100mm in the office here in the garage. Got then as "Seconds" from DD.
A LOT handier than what you are planning and fec all diff in price.

mayoman1973

Having spoke to two builders they have told me doing the insulation seperatly is better for several reasons
- Less waste, you can have any size sheets of insulation and it won't matter as you are boarding over them.
- Less waste because if you damage a sheet where both are bonded then you waste both insulation and plaster board.
- Along external corners you have no waste of your insulation where you have to taper both sheets if you have bonded sheets to get them to meet properly.
- 25% price diff between bonded sheets and gettinig them seperately.
- You can mix up the joints of the insulation boards so they are radom and won't line up with your plaster board sheet joints and tends to crack less.

Al Capwned

mayoman1973 wrote: »

Having spoke to two builders they have told me doing the insulation seperatly is better for several reasons
1- Less waste, you can have any size sheets of insulation and it won't matter as you are boarding over them.
2- Less waste because if you damage a sheet where both are bonded then you waste both insulation and plaster board.
3- Along external corners you have no waste of your insulation where you have to taper both sheets if you have bonded sheets to get them to meet properly.
4- 25% price diff between bonded sheets and gettinig them seperately.
5 - You can mix up the joints of the insulation boards so they are radom and won't line up with your plaster board sheet joints and tends to crack less.

I've fitted probably thousands of insulated slabs... My thoughts on the above.
1. If it's measured up and the slabs cut properly, you should have no more waste than doing it seperately.
2. Takes a lot to damage a slab beyond repair - even if you hit it with a hammer along it's edge for example, you'll do maybe 80/100mm damage - just cut any damage off.
3. No need to cut insulation - slabs will butt up tight against each other with any cutting.
4. No idea of exact prices, tbh.
5. If sheets are fixed to wall properly, and joints scrimmed, you'll not get cracks.

You should speak to a plasterer really, not a builder in my opinion.

Good luck, Al.

mayoman1973

@ Al Capwned
Will there not be insulation exposed on the edge where the boards meet on an external corner , ie around a window reveal for example?

Al Capwned

mayoman1973 wrote: »

@ Al Capwned
Will there not be insulation exposed on the edge where the boards meet on an external corner , ie around a window reveal for example?

If your using a 50mm board for example, cut the insulation back with an old handsaw on the back of one of the slabs 50mm from the edge, ie eseentially leaving the insulation 50mm narrower than the slab.

By doing this, the plasterboard will meet giving a nice, easily beaded corner.
Just something to consider - Make sure that any slabs fitted to reveals dont cover too much of the window/door frame,or interfere with any window sashes or doors. (Also, not forgetting the 3mm approx of skimcoat.)

mayoman1973

I had planned to just fill the joints, sand em and put wall paper liner on the walls. Would that work? Thing is there are a lot of walls that are fine ( A renovation ) but have doorways moved, opened, closed, and I figured the easiest way to avoid having to do a full reskim was to just put liner on the walls.

Al Capwned

mayoman1973 wrote: »

I had planned to just fill the joints, sand em and put wall paper liner on the walls. Would that work? Thing is there are a lot of walls that are fine ( A renovation ) but have doorways moved, opened, closed, and I figured the easiest way to avoid having to do a full reskim was to just put liner on the walls.

Well tbh mate, I would always completely skim a room/wall/ceiling if there is any work done to it, but that's just me. Probably because I'm a plasterer and I like the clean lines etc.... For me, the sign of a good plasterer is not how smooth a wall is (although important), but that all beads and corners are plumb, level and straight. Also that skirting board or picture rails or cornices or whatever can be fitted without any filling behind them, or at least very little. Re-skimming makes sure that I can achieve all that ya know?

I can understand people taping and jointing slabs if on a budget, but for me, I'd always fully skim new slabs. 1 bag of skim will cover approximately 3 slabs fyi.
I've no idea of the cost of wallpaper liner, but my advice would be to gauge that against the cost of the skimcoat and a plasterer.

mayoman1973

Good point,
One last question, if an old doorway has been blocked up and you reskim the entire wall , will you see the track of the newly built blocks against the rest of the wall? My thinking was using liner would be better at covering the newly blocked wall than skim would be?

Al Capwned

mayoman1973 wrote: »

Good point,
One last question, if an old doorway has been blocked up and you reskim the entire wall , will you see the track of the newly built blocks against the rest of the wall? My thinking was using liner would be better at covering the newly blocked wall than skim would be?

Never skim directly on to blockwork.

Couple of options, depending on space available - you could put a sand/cement coat on first, stick a slab to the block, or put bonding plaster down as a basecoat, then skim over the entire wall.

Exact situation would dictate what option to use.

UngratefulWhelp

Lot of interesting info here. Just wondering if I might pose a question of my own. Thinking of going DIY on applying 62mm slabs directly on to the wall with steel mushroom fixings.

Had a guy fit one slab already so I could put in a wardrobe and he just stuck it directly on after drilling the required holes. All my walls are clean and plastered and any unevenness could be dealt with by skim plastering I reckon.

My main concern is dampness getting behind the slabs after reading all the horror stories online. So how do you seal around air vents?

I take it reveals are dealt with in the way already mentioned?

Many thanks in advance