I want to lay a slate hearth on an existing concrete base, which at the moment is flush with the surrounding floorboards. I plan to chisel away the top 10 - 20mm, refill with fresh mortar, level it with the surrounding floorboards and lay the hearth on top. Does this seem reasonable? I'm not sure what ratio of sand and cement to use and whether it should be dry or runny? Thanks, John
Why chisel it away and relay it? Why not lay on existing base?
Well I need some mortar underneath the hearth to keep it in place and at the moment the existing base is flush with the floorboards.
Hearths have to be raised above the floor (if you are going to use the fireplace). IIRC, it's 50mm for a gas fire, and probably something similar for a coal fire.
If you do end up usin mortar its best to use something much softer than the slate, then eventually it can be reused easily without damage. 3:1 lime mortar with 5% cement would do that for you. Common cement mixes would be too hard to make reuse straightforward, and its fairly common for cement mortars to damage stone when it eventually fails.
NT
Would having the hearth flush with the boards mean it is below and carpet? (maybe you don't have carpet). Also with the hearth proud you can just sweep the ash off the edge into a dust pan.
Do you mean slate tiles or a piece of slate? I've done this with a large reclaimed pool-table slate bed :>) and another with a large stone slab, I can echo other respondents comments:-
1) yes check the regs, can't remember a figure but the phrase "discernible difference in level" springs to mind - i.e. you have to be able to "trip up" on it for it to be valid and ironically safer! 2) depending on the "lift" you want and on the size of the hearth stone/slate - you will want either a fairly sloppy or pretty sloppy mix, in a few piles (one each corner and one a big one in the middle - in my case) rather than solid bed which can be a b...h to level. Then with your rubber hammer and spirit level go at it gently and slowly tapping it down to achieve the levels you need. then stop let it go off for an hour or two then tidy up any "squidge" from the edges, then leave to go off proper before putting your fire/ stove on it.Exact mix is unimportant but I'd agree not to make it too cementy as it won't add anything much but would be another b...h to get the hearth up again if you ever have to.
hope it helps
Jim
I've seen several that are flush. What is the point of it being raised? How does that make it safer? And does the same reg apply to those inset fires that people install two or three feet up the wall?
No the hearth won't be flush with the floorboards.
The concrete base at the moment is flush with the floorboards, when I place the 2.5cm thick hearth on top then the top of the hearth will be , well, 2.5 cm higher than the floorboards! I don't have carpet and don't plan to.
Part J has it all - take a look...
for solid fuel appliances:-
2.26 An appliance should be located on a hearth so that it is surrounded by a surface free of combustible material as shown in Diagram 2.10. This surface may be part of the surface of the hearth provided in accordance with Paragraph 2.23, or it may be the surface of a superimposed hearth laid wholly or partly upon a constructional hearth. The edges of this surface should be marked to provide a warning to the building occupants and to discourage combustible floor finishes such as carpet from being laid too close to the appliance. A way of achieving this would be to provide a change in level. =2E.... additionally for gas appliances: 3.40 Appliances should be placed on hearths unless: a)they are to be installed so that every part of any flame or incandescent material will be at least 225mm above the floor; or b)the manufacturer=92s instructions state that a hearth is not required. 3.40 Appliances should be placed on hearths unless: a)they are to be installed so that every part of any flame or incandescent material will be at least 225mm above the floor; or b)the manufacturer=92s instructions state that a hearth is not required.
From having laid some paving the advice seemed to be that it was easier to lay them on an almost dry, very weak mix of sand and cement. The 'blob' approach seemed to be frowned upon in some quarters! Not sure if the same applies to a hearth?
I did already ask:- is it "tiles" or a "slab" that is being laid?? My experiences (already shared) were with slabs (twice)
Were your pavers laid outside?? then damp rising from ground would cure your dry mix - presumably your house is not damp! so there the comparison falters....
Of course YMMV - have a go and report back here how you get on...
never stop learning! Jim
I dont think they do actually.
Having blobs of morter means that you have an air gap. Since air is a good (thermal) insulator this is a good idea with a hearth. For paving it is not such a good idea since it can result in more stress being applied when people walk on the slabs.
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