Masterboard?

[BGEngineer]

Hi, has anyone had any experience with masterboard by promat. I am installing a hole in the wall gas fire and it recommends using this stuff to face the fire front and then to skim over. I have found sheffield insulations do the stuff and they are near me, but its so expensive looking at £100+ for a single sheet of 12mm. Could go down to 9mm and a thicker skim but still this is around £90. Thought about alternatives such as aquapanel with is also non combustible and fire rated 0, any thoughts?

 

[PrenticeBoyofDerry]

glassroc firecase board is 0 rated and 180min fire protection, this board is smooth and can decorated without plaster finish but can be tape jointed or plastered if required but you may be limited with regards to the output heat of the fire you have to whether plaster finish is recommended.
Gyproc fireline is also 0 rated and will also give you at least 30 min fire protection and cost nowhere near that of masterboard, again can be plastered or tape jointed. but heat output of fire could restrict the plastering.

 

[hotrod]

Hi, has anyone had any experience with masterboard by promat. I am installing a hole in the wall gas fire and it recommends using this stuff to face the fire front and then to skim over. I have found sheffield insulations do the stuff and they are near me, but its so expensive looking at £100+ for a single sheet of 12mm.

Yes I've used it 12mm Promat, but I used the Supalux, still a calcium silicate board class0, but it gives 240mins as opposed to 30mins. I paid £110 a board. I can give you loads of advice / hints if you want for using around a hole in the wall fire - I did one earlier this year. There's a load of photos in my album 'Fire' if you're interested.

 

[BGEngineer]

Thanks for the reply guys, I am going to bite the bullet and go with the calcium silicate board but in 9mm. Would be great to have a look at your pics hotrod. Got a couple of questions: Should I use a high temp silicone adhesive to attach the board to the front of the fire? I spoke to the manufacturer and they said this would be ok, otherwise there isn't really going to be a good fixing for the board?

 

[hotrod]

I've sent you a friend request so you can have a look through that 'Fire' album BG as it's set to friends only at the moment. I fixed the supalux to gyplyner framing fixed to the existing brickwork. Have a look through the photos it should all be pretty self explanatory, each step is detailed, and come back with any questions. I'll do my best to help you out, as long as you take your time, and plan each step it's not rocket science.

 

[BGEngineer]

Thanks for that hot rod, was very helpful, just the one I am fitting is a fair bit different, I will get some pics tonight to show you. Interesting, did you skim the superlux or not bother in the end? I know they don't really advised skimming it because it is like a turbo sponge, but if you do it needs 2 applications of pva.

 

[hotrod]

We plastered the supalux with vitcas heat resistant plaster to about 600mm above the fire aperture. The rest of the supalux was plastered with standard multi-finish. If you look at one of the photos in my album you can clearly see where the plaster changes from grey to pink - this is the change from vitcas to multi.

I followed promats MIs on prep for the boards. IE a 'sealing' coat of 5:1 waterva 24hrs prior to plastering and then a 'bonding' coat of 1:3 waterva immediately prior to plastering. That's not a typo it'll go on like glue - it's to kill the suction in the boards. If you do this you will not have a problem skimming the boards, they will come up just fine.

 

[BGEngineer]

Hi Hotrod. Well picked up the supalux today for £92.00 and as I was trying to get the board in the van it snapped in two (( I could have cried. Luckily I still had a bit big enough for what I needed to do. I have included a pic of the fire I am installing, its on 3.5 kw so am just wondering how hot the surrounding area is going to get and wether to use the viscas plaster or not. http://www.freshstartppd.co.uk/currcase.html They have just used finishing plaster, I am not saying its right, but I still need to do a bit of bonding round the supalux and just finishing plaster will be easier.

To give a better idea here are the fires mi's its the Royal Scenic. http://www.siroccofires.com/help-contact/installation-and-user-instructions.html

If you look at page 13, all that metal face is covered by the supalux and then page 16 shows how you need to attach the supalux to the chimney breast wall. I am worried as you can't really attach the supalux to the fire so there is going to be some flex (not good as I plan to have it skimmed) unless I also fix it the the fire face (screw) as well as the front of the chimney.

 

[hotrod]

Hi Hotrod. Well picked up the supalux today for £92.00 and as I was trying to get the board in the van it snapped in two (( I could have cried. Luckily I still had a bit big enough for what I needed to do. I have included a pic of the fire I am installing, its on 3.5 kw so am just wondering how hot the surrounding area is going to get and wether to use the viscas plaster or not. http://www.freshstartppd.co.uk/currcase.html They have just used finishing plaster, I am not saying its right, but I still need to do a bit of bonding round the supalux and just finishing plaster will be easier.

The one I did was 6.5 kw and I tested it after boarding with supalux but prior to plastering. I cranked it up to half 'flame' and left it for 20mins, then turned it off. The supalux board directly above the fire aperture was VERY hot even after the fire had been turned off. That convinced me to use heat resistant plaster. The fire MIs specified heat resistance plaster but they wouldn't specify a brand when asked - so I was, like you a little sceptical. However, if you are going to actually use the fire I have no doubt that the area ~150mm directly above the aperture would fail using a normal gypsum finish plaster. In the example you show above (freshstratppdetc), imho it's a wrong detail.

To give a better idea here are the fires mi's its the Royal Scenic. http://www.siroccofires.com/help-contact/installation-and-user-instructions.html

If you look at page 13, all that metal face is covered by the supalux and then page 16 shows how you need to attach the supalux to the chimney breast wall. I am worried as you can't really attach the supalux to the fire so there is going to be some flex (not good as I plan to have it skimmed) unless I also fix it the the fire face (screw) as well as the front of the chimney.

The fire I did, the supalux doesn't actually touch the appliance at all. There is a 2mm 'expansion' clearance between the edge of the board and the frame flanges. This is an installation requirement as the metal expands and contracts as it heats and cools and obviously if you have the boards touching the appliance there is a chance the plaster can crack as the boards move....I've not read through the MI's to your appliance yet. Leave it with me, it'll be similar to the one I put in I bet. I'll take a look tomorrow.

 

[BGEngineer]

The fire I did, the supalux doesn't actually touch the appliance at all. There is a 2mm 'expansion' clearance between the edge of the board and the frame flanges

The fire I did, the supalux doesn't actually touch the appliance at all. There is a 2mm 'expansion' clearance between the edge of the board and the frame flanges

Exactly this is what I am worried about, although the faces don't seem to be directly affected by heat. I will go and try it out and see how hot it gets.

 

[BGEngineer]

Hotrod, just ran the fire for half an hour on hi flame and the front panels only got slightly warm. it appears they have attached the front panel with the 2mm air gap between the firebox and the front face, so this must be what is keeping it cool, so looks like normal gypsum based plaster should be ok.

 

[hotrod]

If you look at page 13, all that metal face is covered by the supalux and then page 16 shows how you need to attach the supalux to the chimney breast wall. I am worried as you can't really attach the supalux to the fire so there is going to be some flex (not good as I plan to have it skimmed) unless I also fix it the the fire face (screw) as well as the front of the chimney.

Just had a look at this BG, it's pretty similar to the one I did. I would try and get a mechanical fix into the masonry through the masterboard. What about using the gyplyner system (like the one in my album) or similar? I wouldn't try and 'dot n dab' the boards. Are you going to use plasterboards above the masterboard? Would be good to see the install environment so I could advise further / maybe give further advise an how you are going to finish off the adjacent plaster work. I think it's essential you leave a min 2mm expansion gap between the masterboard and the fire flanges though. Don't worry about the board flexing can you not design a suitable frame - first pic in my album is a good example.

 

[hotrod]

Hotrod, just ran the fire for half an hour on hi flame and the front panels only got slightly warm. it appears they have attached the front panel with the 2mm air gap between the firebox and the front face, so this must be what is keeping it cool, so looks like normal gypsum based plaster should be ok.

Fair enough - it' your call, I did note your MI's didn't make reference to heat resistant plaster (mine were quite specific). As a % of the project cost it was 1-2% to use vitcas, so it was a no a brainer for me for peace of mind. BUT it is a pain to use so if I was certain multi would be ok I would definitely use multi. What say you Rich ?