Habito, Fermacell, OSB & Plasterboard, Ply & Plasterboard, or…..

[G and J]

Earlier this week I visited Nick Laslett’s build and he was very generous with his time and patient with my myriad questions.  And as a bonus I now feel I’m not the only Makita obsessed diy-er.  
 

I also realised it has never occurred to me that there may be alternatives to plasterboard other than plaster on blockwork.  How dumb do I get? (No replies on that subject needed, thank you!)

 

Because I’m mildly neurotic, occasionally obsessive and always annoying, and because we have a narrow plot that we want to make the most of we are trying to build with relatively thin walls.  I also like the idea that we could hang pictures and mirrors and stuff anywhere, so I’d focussed on an internal skin of OSB or ply inside my plasterboard.  We have a possibly irrational preference for skimmed walls as well.

 

The benefits of the wood layer beneath the plasterboard are feeling of solidity, maybe a bit better sound attenuation (from outside, internal sound transmission is less of a concern),  and of course the ability to hang stuff on the walls.

 

Nick is using fermacell and he mentioned that habito might also be worth a look.  So after visiting Nick I read all I could find on here about each of those.  

Are there other types of board I should consider?

 

It looks to me like the materials cost is not all that different, and if so, the driver will be optimising the ‘feel’ of our little house.

 

What do you think folks?

[Iceverge]

11mm OSB then 12.5mm plasterboard and skim gets my vote. 

 

You could increase spacing of your studs to 600 cc then. 

 

If you were to move the airtightness layer to the outer sheathing as per my previous post then you could install all wiring in the main stud bays, fit the OSB with whatever depth back boxes suited your electrician, drill a 70mm hole for the cellulose blower in the top of each bay, blow full of insulation and plasterboard over the top. 

 

Then just use slightly longer screws to fit the socket face plates as needed to account for the depth of the OSB and plasterboard. 

 

 

 

[Nick Laslett]

Hello Geoff, I enjoyed your visit. 
 

Here are some good threads from when I was looking at this topic. 
 

 

 

Another product that might be of interest is OSB3 SmartPly from Medite, this has an airtight membrane already attached. 
 

https://mdfosb.com/en/products/smartply-airtight

Forum top tip, you can tag someone to a post by using the @ symbol and their user name, e.g. @G and J, @Nick Laslett, this will then send them a notification. Not something to abuse, but when you are trying to get a specific subject matter expert it can be useful. 

 

 

[G and J]

4 hours ago, Iceverge said:

11mm OSB then 12.5mm plasterboard and skim gets my vote. 

Noted.  Would love to understand the reasoning.

 

4 hours ago, Iceverge said:

You could increase spacing of your studs to 600 cc then.

Presumably you mean my service void studs rather than the main frame studs.  Mind you, I’d love to do the frame on 1200mm centres, it does wonders for the u value.

[G and J]

4 hours ago, Iceverge said:

Then just use slightly longer screws to fit the socket face plates as needed to account for the depth of the OSB and plasterboard. 

One thing I’ve never liked about backboxes for plasterboard is that they become loose when the face plate is unscrewed. Even if fitted before skimming this can happen and it makes a mess.  It did occur to me that the OSB layer may enable me to fix metal backboxes by screwing through side walls into the OSB to avoid that issue. 

[G and J]

Thank you @Nick Laslett (oooh look at me getting all technical!) - added to the reading list.

 

I presume from the existence of airtight OSB that standard OSB isn’t airtight then?

[Kelvin]

OSB can be airtight enough for standard building regs testing. The concern, I think is the sheets can be a bit variable during production. When the walls are pumped with blown cellulose much of the airtightness comes from that. However OSB  is vapour permeable so some people use a different board on the inside and OSB on the outside. There’s a very good thread on here on this very subject. I’ll try and find it. 

Edited June 28 by Kelvin

[Kelvin]

Here it is: 

 

 

[SteamyTea]

5 hours ago, Nick Laslett said:

Medite

I only have experience if their water/moisture proof MDF.

It is an excellent product.

(People may remember I weighted a lump of it, put it in a tub of water for 13 months, left it outside, removed it, wiped the slime off, weighed it again and it had the same mass)

[markharro]

I have used fermacell in our utility room. Just leaving it exposed here but going to experiment using it elsewhere with the fine surface finish

 

[Mike]

On 28/06/2024 at 13:16, G and J said:

Are there other types of board I should consider?

I'm using Gypsotech GopsoLignum, often in 2 layers. It's somewhere above Habito in properties, on the way towards Fermacell. They do have a UK office, but not sure how easy it is to find (I'm using it in France)

 

 

On 28/06/2024 at 19:06, G and J said:

I presume from the existence of airtight OSB that standard OSB isn’t airtight then?

It depends on the brand. Some are, others are not.

[Nick1c]

We went for fermacell walls & PB ceilings due to both the weight of fermacell & the lack of requirement for impact resistance. The insulated timber frame was supplied by PYC & used smartply on the inner face. 
It feels really solid, is great to hang things off & adds to the racking….but the edges aren’t as clean as I had hoped. I am not sure how to make them super sharp, maybe FST on all the edges would work. 
The house is remarkably quiet, the combination of warmcell, a CLT first floor & (possibly)the fermacell) really works. 

[markharro]

Thats just what we are thinking @Nick1c  Did you fit yourself? When you say edges do you mean corners rather than where the boards butt together? I take it you didn't use an edge bead?

[Nick1c]

We had them fitted. Where the sheets butt up is great, it’s the cut edges I am referring to. We have no architrave or skirting which obviously massively exacerbates the problem. As far as I could see if you use beads to clean up the edges you would then have to use a conventional skim rather than the FST. 

[markharro]

Thanks @Nick1c thats very helpful. What you have done is exactly what I am planning and trying to figure out - using Fermacell and a small shadow gap at the bottom where it meets the concrete slab rather than skirting and also a shadow gap detail around doors ie no conventional architrave.

 

I also was hoping to try applying the FST myself rather than getting a plasterer in to skim but I dont know how realistic that is. Have you done the FST skim and if so how did it go?

 

I wondered about using a bead with the FST....is the problem the fact that the FST layer would be too thin to cover the bead properly? I did see a blog where an architect self-builder had used Fermacell and a bead at the bottom but he had then had the boards skimmed by a plasterer.

 

This has got me thinking whether Fermacell could perhaps recommend a bead product that might be compatible with their FST!?

 

PS I dont suppose you could post any photos of how your edges have ended up looking? Thanks

[Nick Laslett]

I am away this weekend, but happy to post pics of various edge finishes, just board, aluminum bead, paper bead. 
 

I did the corner bead and FST for our plant room. I had a tape & jointer do the FST for the rest of the house. 
 

Applying the FST and joint filler to finish fermacell boards is very straight forward. It is just hard work. 

https://www.belmoretools.co.uk/levelline-drywall-corner-tape-2-75-in-x-100-ft-roll.html

[G and J]

1 hour ago, Nick Laslett said:

I am away this weekend, but happy to post pics of various edge finishes, just board, aluminum bead, paper bead. 
 

I did the corner bead and FST for our plant room. I had a tape & jointer do the FST for the rest of the house. 
 

Applying the FST and joint filler to finish fermacell boards is very straight forward. It is just hard work. 

https://www.belmoretools.co.uk/levelline-drywall-corner-tape-2-75-in-x-100-ft-roll.html

Most importantly @Nick Laslett are you happy with the finish?  And was the cost of having tape/jointing/FST done very different from a traditional skim?

[markharro]

Hi @Nick1c and @Nick Laslett sorry to hassle but it would be great to see some photos showing the Fermacell edge finish with and without bead.

 

And @Nick Laslett are you saying you used a bead and then the FST to cover it? How did that work out? Could you apply it thickly enough at the bead to cover it properly?

 

thanks

[Nick Laslett]

5 hours ago, markharro said:

Hi @Nick1c and @Nick Laslett sorry to hassle but it would be great to see some photos showing the Fermacell edge finish with and without bead.

 

And @Nick Laslett are you saying you used a bead and then the FST to cover it? How did that work out? Could you apply it thickly enough at the bead to cover it properly?

 

thanks

No, you use the fermacell joint filler to fix and feather the corner beads. The levelline bead is about 1.5mm thick. 

I will get so pictures after the F1 qualifying. 

[SteamyTea]

I have just been reading about OSB4, which I think meets some airtightness standard or other.

Anyone know more than the marketing BS on the websites.

[Nick Laslett]

My tape and jointer guys used aluminium corner beads. He stapled them onto the fermacell, then used joint filler to create the corner and hide the beads. He used the joint filler over all of the staples/screws and over the jointstick where the boards meet. We did all the boarding ourselves and followed the Fermacell installation instructions to our best abilities. After the joint filler and FST was applied all the boards were lightly sanded.

 

Here are some pictures:

 

1. Ceiling showing stapled aluminium corner beads, with joint filler and FST

 

2. Wall showing joint filler to cover joints and staples with the rest of board covered in FST.

 

3. Corner bead 1.

 

4. Corner bead 2.

 

5. Raw fermacell boards, showing routed corner and fermacell jointstick for the board joints.

 

6. Corner beads before joint filler and FST. Just the screws and joints have been joint filled.

Edited August 31 by Nick Laslett

[markharro]

Thanks @Nick Laslett thats really helpful. Can I ask did you consider omitting a bead at external corners and instead creating a rounded edge with a rasp or similar......just wondering if that is feasible with Fermacell?

 

And did you leave a shadow gap at the bottom of walls? That is the detail I am most interested in seeing with and without a bead. 

[Nick Laslett]

46 minutes ago, markharro said:

Thanks @Nick Laslett thats really helpful. Can I ask did you consider omitting a bead at external corners and instead creating a rounded edge with a rasp or similar......just wondering if that is feasible with Fermacell?

 

And did you leave a shadow gap at the bottom of walls? That is the detail I am most interested in seeing with and without a bead. 

I am going with traditional skirting boards. Never considered a shadow gap, it would also not suit the house style. 
 

You could create rounded edges with a router bit. Never considered leaving the Fermacell without corner beads. Although the boards are strong, I would still worry about the long term wear and tear at corners. 

[JohnMo]

So overall just like dry lining with plasterboard. Dry lining done properly has zero issue with knocks or bangs or scruffs. Personally I am not sure I would use anything else other than plasterboard.

 

Use the correct fixings you can hang whatever you want from plasterboard. We are using 12.5mm plasterboard and have big mirrors hanging from it no issue. Same mirrors were in the last house - no issue in 10 years. 

 

 

[Russell griffiths]

@markharro you can buy a rounded corner bead made purposely for drywall 

you can also get a bead that goes from round back to square for the skirting junction. 
 

look up profile store. 
if you can imagine it then it’s been made and used, it’s only this country that is stuck in 1886, most of the stuff on there is american made for the drywall business.