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

On Jul 26, 11:42*pm, wrote:
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,


Why chisel it away and relay it? Why not lay on existing base?

On 27 Jul, 15:15, mike wrote:
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.

In article ,
writes:
On 27 Jul, 15:15, mike wrote:
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.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

wrote:

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

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

On Sun, 27 Jul 2008 08:07:57 -0700 (PDT), wrote:

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.

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.

--
Cheers
Dave.

On 26 Jul, 23:42, wrote:
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

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

On Jul 27, 6:11*pm, jim wrote:

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!


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?

On 27 Jul, 17:32, "Dave Liquorice"
wrote:
On Sun, 27 Jul 2008 08:07:57 -0700 (PDT), wrote:
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.

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.

--
Cheers
Dave.

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.

On 27 Jul, 18:48, mike wrote:
On Jul 27, 6:11 pm, jim wrote:

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!

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?

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.
.....
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’s 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’s instructions state that
a hearth is not required.

On 27 Jul, 18:11, jim wrote:
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

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?

On 28 Jul, 14:44, wrote:
On 27 Jul, 18:11, jim wrote:



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

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

Andrew Gabriel wrote:
In article ,
writes:
On 27 Jul, 15:15, mike wrote:
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.

I dont think they do actually.

wrote:

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?

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.