Firmacell

[Dee]

Can I use Firmacell as an alternative to Plasterboard in a bathroom? 

If I can, how do you hide the joins?

There are, as usual a number of different options too, which would anyone advise please?

Thanks as always 

Edited October 14, 2023 by Dee

[Redbeard]

Fermacell Fine Surface Treatment, I think it is called. I have only ever used Fermacell once, for a part of IWI to a kitchen where we needed to hang potentially heavy-when-full cupboards on the wall. Instead of 25mm battens over PIR, then plasterboard, we used 25mm ply, then Fermacell, giving us 37mm (? - can't remember F'cell thickness) of hefty stuff (on v long screws) to screw cupbds to. We just had it skimmed in board finish, the same as the surrounding plasterboard.

[nod]

You can tape and joint Firmacell 

I prefer Habito simalar priced 

[nod]

11 hours ago, nod said:

You can tape and joint Firmacell 

I prefer Habito simalar priced 

Just to add 

Firmacell do there own taping compound Gypsum taping compound is fine on there boards 

[Dee]

I'm concerned about weight of cement board. It's an old house and although I want to use it for walls I'm unsure about load bearing. 

What about 6mm insulated cement board?

Can I paint it too? Trying to find alternative to pb and a plasterer!

[Timedout]

I have used Fermacell many times. Just follow the system. All the guidance is there. Use their screws, joint stick, filler and fine surface treatment. I cannot plaster but I can finish a Fermacell wall myself better than any plasterer can finish any plastered wall without making any mess than I cannot vacuum clean. For mounting stuff to walls like a kitchen, utility or bathroom there is no other choice for me. You can screw kitchen units to it, boilers, radiators, inverters. No pilot holes, no plug just 5mm wood screws. 
Yes it is heavy. It’s harder to cut which is why plasterers slag it off. You don’t need edge bead. It is recommended to put SBR on it prior to tiling in humid areas.

I cannot see why a taper edge version is required at all. I have never used it. Personally, I found it is better not to use the jointstick. Simply leave a small gap and fill it with the Fermacell filler. Sand off and then go over with FST using a squeegee. FST is not a skim, it fills the pores and gives a uniform texture.
If painting a good quality paint helps. The decorating lady prefers Johnson’s Jonmatt. Johnson’s Durable Acrylic is good for bathrooms. 

since it was bought out by Hardy outfit, they have tried to kill Fermacell in the U.K. The necessary materials like filler etc became hard to find. It used to come from CCF and the like but is scarce.
Any plasterer you speak to will say it is rubbish but that is because they don’t understand it and never learn. It takes more words than you can fit on a beer mat to explain how to use it. 

[Dee]

So insulation.....I've put a moisture paper and stuffed some old wool insulation batts between the roof rafters in what will be a bathroom and plan PB ontop of that. Is there anything else I need to add for insulation and or Building regs?

[Dee]

Hi anyone,

We built a dormer window to house a bathroom. It is still unfinished. I have a very simple question. The carcass is 2x4 with 25mm ply and Hardy cladding. 

The face wall rattles when I thump it! so I thought I would add 4 x 2 crosswise to strengthen it. Am I wasting my time?

[markharro]

Hi @Timedout I am thinking of using Fermacell and wondered if I could finish it myself with the FST and save on the cost of a plasterer? From what you say that seems possible. What do you mean using a squeegee? Do you think a first time user will get an acceptable final finish? It terms of the stages is it simply screw on with their screws; fill joints with their filler? Do you have apply tape over joins and add filler over that? then finish with the FST? If the boards are not taper edge do you not find the edges stand out a bit after they are filled and taped?

Where is the best place to source the correct ancillary products? thanks

 

Finally is the board robust enough so you dont need any skirting board on top?

 

[Timedout]

It did take me a bit of practice to get the finish but even I managed it. I think Fermacell has or had instructions and videos showing what to do. A bit if trial and error at first but nothing you cannot fix with some fine abrasive paper on a flat sanding pad. 
No tape needed. Fill the  gap with the Fermacell filler. That stuff shrinks so expect a couple of stages. The wetter you make it, the more it shrinks. Make sure it fills the gap, sand off flat to the surface. The instructions say to use jointstick on the factory edges but leave a gap and fill on cut edges. I found the joint stick could smear on  the face as you locate the board and recovering from that is hard as the joint stick is basically like a glue and has a different texture. Overall I get a better finish just using the filler and no joint stick.

you don’t need edge bead. At external corners cut the outer board a little oversize and sand back level. This stuff is hard and it does not flake or crumble like plasterboard so the edges are ok if sanded square and level.
Fermacell do their own squeegee think but I have never had one. I put the FST on with filling knives, I have a 6” and a 10”, and then scrape off using a normal plastic bladed squeegee that I originally bought for windows and getting the drips off the car on the rare occasions I wash it. The FST fills the pores and any minor imperfections, it is not a skim.

I do have a Fermacell cutting knife. It’s just a blade with a single tungsten carbide tip. You scape out a deep line by repeatedly going over with the cutting knife and then snap off. I also use and trash a few hardpoint saws every time. One thing that works for long cuts is one the cheap and nasty circular saws with a multi purpose blade, the ones that can cut through nails. Used with a guide (mine does not have a riving knife so is a bit wayward) it is a quick but messy way of doing a long cut. When you do a snap off edge you get a raggy finish when needs sanding off a bit. I also use one of those little block planes with the replaceable blades but I have seen a contractor using a surform for the same task.

All this is why plasterers hate Fermacell. It puts a lot of the work up front. For me though, it eliminates their messy wet finish and I can screw things directly to it without having to insert extra support in the walls prior to boarding. 
I use it selectively. There is no real point using it everywhere, just use it where it is an advantage. I have only used the 12.5mm boards. The 10mm boards may be easier to handle.
I have usually got the stuff through Travis Perkins but they source it from CCF (Contract Ceiling Factors) who are part of the same group. I have bought Fermacell compatible screws from a seller based in the Netherlands. They worked just as well and were less expensive. I think Toolstation’s European arm used to sell them, I have also bought Fermacell stuff from the big insulation outfits. I think one was Minster (part of Sant Gobain) but I may be mistaken. I just have recollection of going to their Truro depot. Another of the insulation sellers was selling it online and delivered, I recall being impressed that the boards were all in perfect order and the driver understood how to handle it. They are so heavy they can break under their own weight so do not go to wild when moving them.
A good TP branch willing to talk to their partners at CCF should be able to help. CCF are a good source of dry-lining metal profiles too. I am an advocate of Gypliner type products, very useful stuff.
 

[markharro]

Hi @Timedout I am interested to know if you think Fermacell is robust enough to use right down to our concrete floor without a skirting board to get a simple clean look? thanks

[markharro]

Can no one comment on whether Fermacell is robust enough to use right down to our concrete floor without a skirting board to get a simple clean look?

 

Also I have another question. We are using 12mm ply on the bottom half of a wall as a feature secured with quite big screws - again as a feature. The screws are 6mm diameter I think and have concentric ridges under the head designed to allow you to adjust the plane of the board so you can easily match up boards. I intend to use Fermacell over the ply and want to use the same screws to maintain the "look". Will this cause any issues ie could I destroy the edges of the Fermacell with these large screws? Would it be ok if I predrilled a hole first and maybe also a taper at the surface?

 

thanks

[Jenki]

The main reason for skirting boards is to creat a nice finish , board up to ceiling, packed at bottom, then skirt to finish.

I'd see the main issue getting a nice finish at both ceiling and floor.

I can't comment on if the  Fermacell will wick any moisture from the concrete.

[Nick Laslett]

On 28/10/2023 at 10:17, markharro said:

Hi @Timedout I am interested to know if you think Fermacell is robust enough to use right down to our concrete floor without a skirting board to get a simple clean look? thanks

I don’t think it would be recommended, but you could do it. Their Orange Book wants the boards with at least a 6mm gap from the floor. The boards are more water resistant than standard plasterboard, but are still designed to be kept dry, might need to seal the edges or something similar. A 12.5mm board, after FST and painting is easily robust enough to not need the addition of a skirting board. 
 

 

[Nick Laslett]

On 14/11/2023 at 21:03, markharro said:

Can no one comment on whether Fermacell is robust enough to use right down to our concrete floor without a skirting board to get a simple clean look?

 

Also I have another question. We are using 12mm ply on the bottom half of a wall as a feature secured with quite big screws - again as a feature. The screws are 6mm diameter I think and have concentric ridges under the head designed to allow you to adjust the plane of the board so you can easily match up boards. I intend to use Fermacell over the ply and want to use the same screws to maintain the "look". Will this cause any issues ie could I destroy the edges of the Fermacell with these large screws? Would it be ok if I predrilled a hole first and maybe also a taper at the surface?

 

thanks

Not sure if the screws will be a problem, as long as you are 12mm in from the edge, it should be okay. 
 

Fermacell is nothing like plasterboard, I would describe it as being a cross between cement board and chipboard. It is less brittle and less hard than cement board. The fibres are finer than chipboard, but not as fine as MDF. It does sand nicely and most woodworking techniques work on it. It holds a screw better than chipboard or Mdf. 12.5mm boards can take a weight of 30kg on a single screw.  
 

Basically you need to buy a sheet, and have a play with it. 

[markharro]

1 hour ago, Nick Laslett said:

Basically you need to buy a sheet, and have a play with it. 

I just have - and used it high up a wall. As others have said its very dusty to cut but it is pleasingly robust - and heavy! Not tried one of my oversize screws yet - will experiment once I am down to wastage scraps. Yes I understand the logic behind skirting boards but just don't like them. Am going to try the fermacell with a 10mm gap at bottom as shadow gap I think.