Stove installation and hearth query

[pebble77]

Hi all

 

So I am planning on installing a small multifuel on my boat soon and am making plans on building the hearth.

I have the instructions about dimensions and air gaps etc etc but need advice on materials.

 

I have been recommended using slabs of either slate or concrete or granite as an easy base for the stove to sit on. Is this the case?

I have sourced a cheap slab of granite that is about 600 x 600 and 40mm thick... is this too heavy when combined with the stove on one side of the boat?

 

I know I could tile but I was just thinking of doing that for ease and have fire board and tile on the wall behind after stove is in... any thoughts?

 

TIA

[blackrose]

40mm sounds a bit thick to me. The slab itself can be stuck down with Stixall, CT1, etc, but you need to drill through the feet of the stove and through the slab and put some stainless coach bolts right through into the floor to hold the stove in position - unless you have some other means of doing so?

 

Since you already have the granite slab, position it where it would be going in the boat along with the stove and go outside to have a look at how much it's listing. Then rearrange other heavy stuff on board including ballast if necessary to see if you can rectify the list. If the slab ends up causing more trouble than it's worth just get rid of it and stick some tiles down. I used large slate effect tiles.

 

Edited October 12, 2023 by blackrose

[Tony Brooks]

I have a problem with the advice about sticking tiles down. You need to see what standard the STOVE was built to. Some demand a thickinsh fireproof base, while other (often with an ash pan area and on legs)  have a lesser requirement. If the stove is of the latter type, then just sticking tiles to the flooring would be asking for a boat fire.

 

Also try drilling the granite slab before heaving it about, it could be difficult.

[Chewbacka]

3 hours ago, Tony Brooks said:

I have a problem with the advice about sticking tiles down. You need to see what standard the STOVE was built to. Some demand a thickinsh fireproof base, while other (often with an ash pan area and on legs)  have a lesser requirement. If the stove is of the latter type, then just sticking tiles to the flooring would be asking for a boat fire.

 

Also try drilling the granite slab before heaving it about, it could be difficult.

I think you mean the former.

[pebble77]

Hi, thanks for the replies.

I would assume I'd have to tile on fibreboard if I was going that way. And it has to be raised a certain amount off the floor etc.

 

I don't have the granite yet, I was going to pick it up tomorrow from Facebook marketplace tomorrow. But might wait and see if something a but thinner comes up.

[Rincewind]

Use the Granite slab.  It will not be too heavy for the boat and as blackrose pointed out you can always re-ballast.  

 

I have recently rebuilt my fireplace / hearth and the advice given to me by several stone merchants was to use Granite because it it the only material that can withstand heat well.  Materials such as marble can crack if subjected to high heat and other stone/quarried composites typically used for kitchen worktops etc. can contain plastic resins which will melt and deform.  If using tiles, the advice I was given was to use porcelain. 

I chose to use 30mm granite and used it for the sides and mantle as well.  My stone merchant cut it to my requirements / measurements adding beveled edges and drilling holes through the base (for securing the stove) at no extra cost - template required.  For small projects such as this, some stone merchants may offer you "off cuts" of granite from larger projects at a fraction of the normal cost.  Always ask and shop around for best prices.

 

My method of installing a heat barrier between the hearth and the wooden floor was to fix a 50mm concrete paving slab to the floor with several wood screws so it could not move, then the granite slab was placed on top, overlapping the concrete slab by 25mm or so.  This arrangement raised the granite hearth sufficiently to give an aesthetic appeal as well as providing a heat barrier.  

The stove was fixed to the hearth by using sleeve anchor bolts driven through the granite (clearance holes in the granite) to anchor into the concrete slab.  The sides were stood and fixed in position on the hearth, with heat barrier material behind the vertical slabs.  Joints sealed with fireproof mastic.

[Tony Brooks]

I just tiled a paving slab that I screwed to the floor with long screws and packing pieces. A washer between the packing tube and screw head allowed me to secure the stove legs to the screws with worm drive hose clips.

40 minutes ago, Chewbacka said:

I think you mean the former.

 

Yes, thanks.

 

FWIW I think I found that information in the Building Regulations, so not directly applicable to boats, but well worth keeping in mind pyrosis of the floor board wise.

[Tracy D'arth]

I have found that below Morso Squirrel fires the temperatures are very low even with the stove over-fuelled  and burning hot.

In fact my stove has shorter than standard legs and I keep a spare door glass under there; still in its card wrapper. Its not even scorched.

I have always found quarry tiles suitable. Its the substrate that matters behind tiles.

[magnetman]

I used a cast iron manhole cover (with surround) for a fire once. surround bolted to boat floor raised in hardwood bars then manhole cover bolted to fire then slotted into the surround. 

 

Worked well and to my eye looked alright as well. 

 

Edited October 12, 2023 by magnetman

[pebble77]

2 minutes ago, magnetman said:

I used a cast iron manhole cover (with surround) for a fire once. surround bolted to boat floor raised in hardwood bars then manhole cover bolted to fire then slotted into the surround. 

 

Worked well and to my eye looked alright as well. 

 

That sounds amazing! 👌 

20 minutes ago, Rincewind said:

Use the Granite slab.  It will not be too heavy for the boat and as blackrose pointed out you can always re-ballast.  

 

I have recently rebuilt my fireplace / hearth and the advice given to me by several stone merchants was to use Granite because it it the only material that can withstand heat well.  Materials such as marble can crack if subjected to high heat and other stone/quarried composites typically used for kitchen worktops etc. can contain plastic resins which will melt and deform.  If using tiles, the advice I was given was to use porcelain. 

I chose to use 30mm granite and used it for the sides and mantle as well.  My stone merchant cut it to my requirements / measurements adding beveled edges and drilling holes through the base (for securing the stove) at no extra cost - template required.  For small projects such as this, some stone merchants may offer you "off cuts" of granite from larger projects at a fraction of the normal cost.  Always ask and shop around for best prices.

 

My method of installing a heat barrier between the hearth and the wooden floor was to fix a 50mm concrete paving slab to the floor with several wood screws so it could not move, then the granite slab was placed on top, overlapping the concrete slab by 25mm or so.  This arrangement raised the granite hearth sufficiently to give an aesthetic appeal as well as providing a heat barrier.  

The stove was fixed to the hearth by using sleeve anchor bolts driven through the granite (clearance holes in the granite) to anchor into the concrete slab.  The sides were stood and fixed in position on the hearth, with heat barrier material behind the vertical slabs.  Joints sealed with fireproof mastic.

Thanks so much for taking the time to write this. Really really useful 

14 minutes ago, Tony Brooks said:

I just tiled a paving slab that I screwed to the floor with long screws and packing pieces. A washer between the packing tube and screw head allowed me to secure the stove legs to the screws with worm drive hose clips.

Great idea! If the granite is too heavy I'm definitely doing this.

 

23 minutes ago, Rincewind said:

Use the Granite slab.  It will not be too heavy for the boat and as blackrose pointed out you can always re-ballast.  

 

I have recently rebuilt my fireplace / hearth and the advice given to me by several stone merchants was to use Granite because it it the only material that can withstand heat well.  Materials such as marble can crack if subjected to high heat and other stone/quarried composites typically used for kitchen worktops etc. can contain plastic resins which will melt and deform.  If using tiles, the advice I was given was to use porcelain. 

I chose to use 30mm granite and used it for the sides and mantle as well.  My stone merchant cut it to my requirements / measurements adding beveled edges and drilling holes through the base (for securing the stove) at no extra cost - template required.  For small projects such as this, some stone merchants may offer you "off cuts" of granite from larger projects at a fraction of the normal cost.  Always ask and shop around for best prices.

 

My method of installing a heat barrier between the hearth and the wooden floor was to fix a 50mm concrete paving slab to the floor with several wood screws so it could not move, then the granite slab was placed on top, overlapping the concrete slab by 25mm or so.  This arrangement raised the granite hearth sufficiently to give an aesthetic appeal as well as providing a heat barrier.  

The stove was fixed to the hearth by using sleeve anchor bolts driven through the granite (clearance holes in the granite) to anchor into the concrete slab.  The sides were stood and fixed in position on the hearth, with heat barrier material behind the vertical slabs.  Joints sealed with fireproof mastic.

So the granite is a leftover piece of worktop. Does that mean it might be a composite and not fit for purpose?

[Rincewind]

1 hour ago, pebble77 said:

So the granite is a leftover piece of worktop. Does that mean it might be a composite and not fit for purpose?

No, not always, but see below,

 

Granite is a natural material quarried from the earth  (actually formed when the the earths tectonic plates collide or ride over each other with immense pressure). e.g. earthquakes.

Other quarried materials are formed from volcanic eruptions and land mass movements etc.

Granite is used in its natural form to create worktops, as are other quarried materials such as marble and quartz 

 

Composite materials are also used for worktops that have the appearance of marble or granite but they are man made, insomuch as the quarried material is combined with resins and suchlike to form a composite material that offers a much lower cost to the consumer. i.e. cheaper worktops.  Which is why trivets are recommended for use with these types of worktop, otherwise hot saucepans will damage the surface.

 

If a stone merchant (kitchen worktop manufacture) cuts a substantial sized worktop from a quarried slab of genuine granite, some of that slab is left over and described as an 'Off Cut'.  The off cut may not be large enough to form another worktop so they are put to one side and offered for sale at lower cost in order to recoup the initial cost of the quarried slab.

 

Be aware though, that a composite material may have the appearance of granite without it actually being so.  Best to ask a bona fide stone merchant if you are in any doubt, they are obliged to tell you before you purchase.

[blackrose]

6 hours ago, Tony Brooks said:

If the stove is of the latter type, then just sticking tiles to the flooring would be asking for a boat fire.

 

No it wouldn't. Heat rises don't you know. My tiles under the stove don't even get hot, but if you want you can always stick the tiles to Masterboard or some other fireproof board. My original advice didn't exclude that.

2 hours ago, pebble77 said:

Hi, thanks for the replies.

I would assume I'd have to tile on fibreboard if I was going that way. And it has to be raised a certain amount off the floor etc.

 

How are you going to raise a stove off the floor and support it adequately? A raised ply base just brings you back to square one and is completely pointless.

 

There are some ways to do it but most will still involve combustible materials directly under the fireproof board so you may as well just put some fireproof board down on the floor.

Edited October 12, 2023 by blackrose

[magnetman]

One of my fires, which is a custom made unit, has a flat base rather than legs and even sitting on a piece of 2 inch thick paving slab the same footprint the whole slab gets very hot. 

 

Of course it is not a normal fire and does burn hot because we put preheated secondary air tubes on it but yes some fires it not on legs are capable of burning wood through floor tiles. 

 

 

 

I would personally want something more durable than tiles under the fire. 

Edited October 12, 2023 by magnetman

[blackrose]

2 hours ago, Tracy D'arth said:

I have found that below Morso Squirrel fires the temperatures are very low even with the stove over-fuelled  and burning hot.

In fact my stove has shorter than standard legs and I keep a spare door glass under there; still in its card wrapper. Its not even scorched.

I have always found quarry tiles suitable. Its the substrate that matters behind tiles.

 

Yes. My Morso Panther is the same. I never used fireproof board under the floor tiles.

[magnetman]

I think the ideal solution if you definitely don't want to ever move the fire would be to cut out the floor and fit a thick stone slab to just above floor level the right size for the fire then put nice encaustic tiles around to catch any excess ash. 

 

You do have to be confident you don't want to move the fire and also need to find a space without any framing. Should be doable if the spacing is 18 inches. 

 

 

[blackrose]

4 minutes ago, magnetman said:

 but yes some fires it not on legs are capable of burning wood through floor tiles. 

 

Not many that are commonly found in boats. But as I said, the OP should just put down fireboard and tile on top if it's a concern.

[magnetman]

I think the ideal solution if you definitely don't want to ever move the fire would be to cut out the floor and fit a thick stone slab to just above floor level the right size for the fire then put nice encaustic tiles around to catch any excess ash. 

 

You do have to be confident you don't want to move the fire and also need to find a space without any framing. Should be doable if the spacing is 18 inches. 

 

 

Or use the manhole cover. When I did it this was all above floor level but thinking back it would have been better to cut the floor and get the manhole cover just clear of floor level. 

 

This has an extra advantage of introducing heat into the bilges which will never be a bad idea. 

[blackrose]

1 minute ago, magnetman said:

I think the ideal solution if you definitely don't want to ever move the fire would be to cut out the floor and fit a thick stone slab to just above floor level the right size for the fire then put nice encaustic tiles around to catch any excess ash. 

 

You do have to be confident you don't want to move the fire and also need to find a space without any framing. Should be doable if the spacing is 18 inches. 

 

 

 

I find the floor 2ft in front of most stoves gets much hotter than the floor directly under the stove. And yet nobody bothers protecting that area at all and many people have carpet there. So perhaps we're overthinking things a bit... Just an observation.

[magnetman]

 

I suppose the Rolls Royce setup if you wers starting from a steel shell would be to weld in a platform for the fire of thick steel bridging across lateral structural members. That would be Really Good then bolt fire to that. Sorted. 

 

 

 

Arrange the platform to be just slightly higher than the floor and one could weld a round bar around it to catch the ash. 

[blackrose]

It's getting even worse! 🤣

[Rincewind]

2 hours ago, magnetman said:

I used a cast iron manhole cover (with surround) for a fire once.

Was that your escape route into the canal in case of a fire onboard? 🤣

[Tony Brooks]

42 minutes ago, blackrose said:

 

No it wouldn't. Heat rises don't you know. My tiles under the stove don't even get hot, but if you want you can always stick the tiles to Masterboard or some other fireproof board. My original advice didn't exclude that.

 

 

Ah, so your science lessons taught you nothing about conduction of heat. "Heat rises" relates to convection in a gas or liquid. Radiated heat goes in all directions up, down sideways. I am sure that you are very badly wrong with this. It all depends upon the design of the stove.

[pebble77]

3 hours ago, Rincewind said:

Use the Granite slab.  It will not be too heavy for the boat and as blackrose pointed out you can always re-ballast.  

 

I have recently rebuilt my fireplace / hearth and the advice given to me by several stone merchants was to use Granite it it the only material that can withstand heat well.  Materials such as marble can crack if subjected to high heat and other stone/quarried composites typically used for kitchen worktops etc. can contain plastic resins which will melt and deform.  If using tiles, the advice I was given was to use porcelain. 

I chose to use 30mm granite and used it for the sides and mantle as well.  My stone merchant cut it to my requirements / measurements adding beveled edges and drilling holes through the base (for securing the stove) at no extra cost - template required.  For small projects such as this, some stone merchants may offer you "off cuts" of granite from larger projects at a fraction of the normal cost.  Always ask and shop around for best prices.

 

My method of installing a heat barrier between the hearth and the wooden floor was to fix a 50mm concrete paving slab to the floor with several wood screws so it could not move, then the granite slab was placed on top, overlapping the concrete slab by 25mm or so.  This arrangement raised the granite hearth sufficiently to give an aesthetic appeal as well as providing a heat barrier.  

The stove was fixed to the hearth by using sleeve anchor bolts driven through the granite (clearance holes in the granite) to anchor into the concrete slab.  The sides were stood and fixed in position on the hearth, with heat barrier material behind the vertical slabs.  Joints sealed with fireproof mastic.

So the granite is a leftover piece of worktop. Does that mean it might be a composite and not fit for purpose?

Ignore the above.

 

The stove is on legs. My boat has never had a burner on so I have freedom of where to put it, with in reason.

 

[Rincewind]

11 minutes ago, pebble77 said:

he stove is on legs. My boat has never had a burner on so I have freedom of where to put it, with in reason.

More of a statement than a question!

Where to place the stove within the boat needs many considerations, there are many views on this and you will probably never get a definitive answer.  This has been discussed before on the forum and you may well find that using the search box on the home page may help you decide.  Your outside roof space may also be a deciding factor that should not be overlooked.

[pebble77]

Yes I understand. Someone is coming to have a look and give me advice on it this weekend.