Fireboard

[Johny London]

I've been researching the install of my stove and have found a number of very good guides. One of them recommends the use of 25mm calcium silicate board with a 10mm air gap behind it, for the sides of where the stove is, and I like the sound of that. I can't find that type of board anywhere other than online (TP though, do a 9mm full sheet for silly money) but did find Wickes have Knauf Fire Panel (a kind of better version of plasterboard) in 12.5mm, so I could double that up. My question is - should I hang out for the calcium silicate or would the Wickes stuff be suitable?

I'm going to use 300mm slate tiles for both under the stove and on the fireboard surrounds.

 

While I'm at it - unsure whether to remove the ply floor and build up in brick all the way from the boat base plate, (for the hearth) or whether I can use a similar method (25mm fireboard and an air gap) under the stove.

 

thanks in advance!

[Richard T]

Midland Chandlers and Sheffield Insulation sell it. A vermiculite board would also probably work. It is insulation that is required as well as being non combustible.

[BargeeSpud]

Most stove insulation on boats is done using Promat Masterboard which is available at TP at a reasonable price & you should be able to double up enough for your surround to give a thickness of 12mm from a single sheet if thats what you want to do.

 

Most of the time a single layer is used which is then covered with ceramic fire tiles which is adequate as the objective is to prevent heat from the stove raising the temperature of the underlying wood to its flashpoint which depending on its type can be between 200 & 300 degrees C. Now under most conditions when using a solid fuel stove on a boat, you will be able to get a kettle sitting on top of one to boil, but not to boil so that its screaming its whistle out, it'll be more simmering than boiling, so not getting much above 100 degrees C. Therefore, I would suggest that a normal 6mm layer of Masterboard covered in fire tiles is more than adequate.

 

The same applies to the hearth & there shouldn't be any need beyond doubling the thickness of the floorboard for any extra floor reinforcing, In fact building the hearth from a standard 15/20mm ply board should do it.

 

Don't forget that all these guides for installing solid fuel stoves are as for installing in a domestic situation & tend to be over "engineered".

 

Edited to add:

 

Forget the air space. not only unnecessary, but wastes a lot of space. See my point re the kettle above, you'll rarely get your stove up to full output if ever. I never have after nearly 20 years of using stoves on boats.

 

Edited again to amend my kettle example!

Edited October 9, 2016 by BargeeSpud

[Sea Dog]

Now under most conditions when using a solid fuel stove on a boat, you will be able to get a kettle sitting on top of one to boil, but not to boil so that its screaming its whistle out, it'll be more simmering than boiling, so not getting much above 100 degrees C.

Spud, I don't wish to contradict, but you're a bit low with your potential stove/flue surface temperature. A stove thermometer will show that the optimum burn will give a surface temp between 150 and 250 degrees C (something like 250 to 450 F) and higher is quite easily achieved given a strong enough draw.

[Chewbacka]

Be careful as a fire surround designed for your stove gently burning away keeping the boat warm may not be enough if you fall asleep whilst getting your stove going with the air vent wide open. To wake to a stove roaring away will be frightening, but not to wake up at all because the wood behind the fire place is overheated and smouldering and emitting lots of CO is not what you want. The fire surround has to be able to cope with the occasional accident as well as normal operation.

[BargeeSpud]

Spud, I don't wish to contradict, but you're a bit low with your potential stove/flue surface temperature. A stove thermometer will show that the optimum burn will give a surface temp between 150 and 250 degrees C (something like 250 to 450 F) and higher is quite easily achieved given a strong enough draw.

 

Fair enough, I stand corrected, my summation was based purely on observation under the stove settings that I normally use.

 

Your figures still indicate, IMHO, that a single thickness of Masterboard covered in fire tiles will provide more than adequate protection to the underlying wood provided that the recommended distances from the sides of the stove to the surround can be achieved.

[BargeeSpud]

Be careful as a fire surround designed for your stove gently burning away keeping the boat warm may not be enough if you fall asleep whilst getting your stove going with the air vent wide open. To wake to a stove roaring away will be frightening, but not to wake up at all because the wood behind the fire place is overheated and smouldering and emitting lots of CO is not what you want. The fire surround has to be able to cope with the occasional accident as well as normal operation.

 

Fair point well worth raising, we've all been distracted whilst getting the stove stoked back up & found it roaring away later.

 

However, you can take safety to extremes if you allow for every potential eventuality & you can make the installation highly impractical (& hideously expensive) as a result. You have to weigh up the chances of hazard & if you think risks will be too great, then leave well alone.

 

As an aside, the 6mm thickness of Masterboard is claimed to withstand fire for 30 minutes, so I guess it would be reasonable to suppose that the time increases incrementally with each successive layer. I'd be interested to know how much this time is increased, if at all, when the material is covered in fire tiles.

[Chewbacka]

 

Fair point well worth raising, we've all been distracted whilst getting the stove stoked back up & found it roaring away later.

 

However, you can take safety to extremes if you allow for every potential eventuality & you can make the installation highly impractical (& hideously expensive) as a result. You have to weigh up the chances of hazard & if you think risks will be too great, then leave well alone.

 

As an aside, the 6mm thickness of Masterboard is claimed to withstand fire for 30 minutes, so I guess it would be reasonable to suppose that the time increases incrementally with each successive layer. I'd be interested to know how much this time is increased, if at all, when the material is covered in fire tiles.

Interesting points. This is more complex than it first appears. Fire board is to prevent the rapid spread of fire, so may be rated for 3omins before fire breaks out on the other side. But for a boat you are looking at long term heat. In the case of wood it can degrade over a long period of time and then catch fire at much lower temperatures than in a house fire situation where the wood is undamaged. Look up pyrolysis which shows that wood degrades at about 200c which is not very hot. So whilst I agree that the 25mm thick calcium silicate board design has a good safety margin, I would be wary of using a 6mm not very insulating fire board to protect my wood unless there was a large air gap on both sides for ventilation.

[BargeeSpud]

I've had Masterboard on 2 boats now with no apparent issues. In fact, on my 1st boat, I rebuilt & slightly enlarged the original fire surround and found the underlying wood behind the masterboard had no signs of scorching from the stove, even where it was about 10cm from the surround at the stove rear corners. I will say however, that the tiles were made by Stovax & had been fitted with silicon blobs - an absolute b*****d to get off, so maybe the small 2mm or so air gap between the tiles & Masterboard helped even though there was no ventilation. Anyway, I was lucky to be able to get some more of the same tiles & fixed them to the new masterboard & surround with a silicon adhesive as before.

 

Personally, I think that any really effective air gap would need to be so large as to have too much of an impact on the cabin space & the OP's guide is talking about 35mm + any backing board & decorative tiles which could easily double this to 60mm +, far too much IMO. My own fire surround is 30mm which includes 15mm backing board, 6mm Masterboard, cement & fire resistant tiles, which to me is just about right.

 

I also have to say that Masterboard is used by a lot of boat builders & is really good stuff in my experience and I'd have it as a 1st choice every time, so don't rule it out.

Edited October 9, 2016 by BargeeSpud

[rjasmith]

I went for the 25mm calcium silicate and bought some from John Opies (see their website via Google) They sell it as Skamolex Blue which is a Scandinavian trade name. John Opie used to be almost the only UK importer and I don't think their prices were too bad but it was a while ago. There may be other suppliers nowadays.

 

I regret to say that I still haven't completed the installation but it will be fully compliant with the BS 8511 fire surround recommendations when I do!

 

Richard

[BargeeSpud]

I regret to say that I still haven't completed the installation but it will be fully compliant with the BS 8511 fire surround recommendations when I do!

 

Richard

 

Interesting, but BS 8511 is a code of practice (Isee you've correctly referred to them as "recommendations") which does not seem to be a requirement under the BSS. HOWEVER, the BSS does give BS8511 the caveat that "The code isn't compulsory, but will always be referred to if an accident occurs".

 

The bottom line is that you, me, the OP or anyone else has to do what they feel is right for them. If that means sticking rigidly to BS8511 or ignoring it totally, then thats great. All I've been saying is that there are other materials out there that will do a great job. You pays your money & takes your choice.

Edited October 9, 2016 by BargeeSpud

[Dave Payne]

Picked mine from eBay, not cheap though. 25mm x 1000mm x 610mm think it was £36 a sheet, search eBay for skamotec.

[ditchcrawler]

 

Interesting, but BS 8511 is a code of practice (Isee you've correctly referred to them as "recommendations") which does not seem to be a requirement under the BSS. HOWEVER, the BSS does give BS8511 the caveat that "The code isn't compulsory, but will always be referred to if an accident occurs".

 

The bottom line is that you, me, the OP or anyone else has to do what they feel is right for them. If that means sticking rigidly to BS8511 or ignoring it totally, then thats great. All I've been saying is that there are other materials out there that will do a great job. You pays your money & takes your choice.

But what about this http://www.canalworld.net/forums/index.php?showtopic=81090#entry1711589

[BargeeSpud]

But what about this http://www.canalworld.net/forums/index.php?showtopic=81090#entry1711589

Forgive me, but I don't see what point you're trying to make. I read nothing in that article that hasn't already been raised here. In fact it confirms what I've said regarding BS8511.

[ditchcrawler]

Forgive me, but I don't see what point you're trying to make. I read nothing in that article that hasn't already been raised here. In fact it confirms what I've said regarding BS8511.

That is because I posted it on the wrong thread, it should have gone to the one about back cabin stoves.

[BargeeSpud]

That is because I posted it on the wrong thread, it should have gone to the one about back cabin stoves.

I'd laugh but I've done that myself! There but.....etc.,etc.

[Johny London]

Interesting to see such a wide range of views and methods.

 

I'm particularly interested to know if anyone has experience with the Wickes Knauf board, because I can go along and pick it up. Everything else (for the calcium silicate) is order only (except tp) and as it is very cold aboard now I wanted to get everything for the hearth asap and ideally have all that side of it done by the time the flu stuff I'm ordering arrives. I've no heating otherwise

[Johny London]

Ive used this: http://www.soliftec.com/Boat%20Stoves%201-page.pdfas a starting point - it does say that board without gap is no use.

 

Also this: http://www.boatsafetyscheme.org/stay-safe/solid-fuel-stoves/new-stove-new-chimney/

 

And in my case as its a Morso the stove installation guide for a Squirrel.

[nb Innisfree]

No one has mentioned ventilating an air gap, would be an improvement.

[cuthound]

When I was working, the company I last worked for built data centres.

 

Each data hall separated from the next one by building a 2" x 2" timber frame, insulating it with rock wool and cladding each side with a 2 sheet thickness of plasterboard. All gaps sealed with intumescent sealant. In order to confirm compliance with section 20 of the London Building Regulations each hall was inspected and signed off by the local councils fire officer, certifying a 2 hour fire rating.

 

So why can't 2 sheets of plasterboard with an airgap be used instead of this expensive fireboard?

 

Edited to add a missing worm.

Edited October 10, 2016 by cuthound

[WotEver]

A 2 hour fire break is an entirely different beast to an insulating layer designed to keep wood below its charring temperature.

[Johny London]

I also found this, which has rather good details of getting the flu through the roof...

 

http://walkerstug.blogspot.co.uk/2012/08/saloon-stove-flue-roof-collar-and.html

[ditchcrawler]

I also found this, which has rather good details of getting the flu through the roof...

 

http://walkerstug.blogspot.co.uk/2012/08/saloon-stove-flue-roof-collar-and.html

That is a good build blog. some good ideas in there.

[rjasmith]

I also found this, which has rather good details of getting the flu through the roof...

 

http://walkerstug.blogspot.co.uk/2012/08/saloon-stove-flue-roof-collar-and.html

 

Indeed that link does! But they did a "Rolls Royce", fully compliant to BS 8511 Code of Practice, installation for that project. You may have seen that they used Super Isol (or Skamolex Blue) fireboard which you mentioned right back at the start!

 

The flue system is the one designed by Roy Willoughby (Warstock Developments) which I had a look at several years ago soon after he produced it. The flue is double skin and insulated but together with his own design of roof collar and chimney is intended purely for use on canal boats unlike other makes of double skin flues which often use adaptations of household components.

 

Roy's system is obviously very splendid but is also quite pricey!

 

I get the impression that the you would prefer to do something cheaper/simpler which is probably fine bearing in mind that BSS 8511 is not mandatory for either BSS or RCD, just a statement of good practice. The Soliftec drawing is a precis of BS 8511.

 

Richard

Edited October 10, 2016 by rjasmith

[Johny London]

Well, I guess I was after doing things safely on a budget, and perhaps the two things are not compatible, or not entirely!

I've found the Morso flu kit complete for £499 delivered, which isn't bad, and I found a 1200x1200 25mm board for £50, on top of that theres just bricks for hearth (height) tiles and cement. I'm just having a last look at the standard twin wall flu stuff (ie Shieldmaster) to see if I can make that work (for about half the cost of the Morso kit) but I'm unclear on the coupling to the stove and the roof plate thing, so the kit at least means it will all go together. Plus, I can get on and build the hearth while I wait for it to arrive as the Morso kit is adjustable, no need to worry about trying to calculate angled heights to the mm.