Replacing a slate hearth

[Joelaw]

Our fireplace (old style iron combination - all in one piece - 40" wide and 38" tall)) has a slate hearth 2.5 cm thick which I assume has been mortared into place but which is chipped and cracked. We don't use the fire but it looks nice apart from the hearth. I want to replace the hearth but don't want to remove the fireplace from the wall as I know it's been backfilled. I can feel behind the fire in the fireplace opening the void has been filled and mortared and so if I take the fireplace off the wall there'll be a lot of mess and I'll have to replace the rubble behind it.

I was thinking that as it's well screwed into the wall I could chip away the slate. When it comes to removing the slate under the pillars of the fireplace (the bits that the fireplace is standing on the hearth with at the front) I can get a strong mate to help support the fire in addition to the wall fixings while I chip away underneath. When all the slate has been cleared I can then slide in a new hearth of the same depth as the old one.

Can anyone let me know if this is possible? Also how easy is it to separate the slate hearth from the constructional hearth underneath? Is slate easy to drill/break with a cold chisel etc to allow me to remove it in pieces?Thanks a lot for any advice.

 

[Bondai]

I dont claim to have done this myself but for what it's worth...

Just wandering how much weight the hearth is taking.

If the fireplace is fixed to the actual wall surrounding it then at least you can be sure it will remain where it is so long as it has sufficient support. I wouldnt depend on these fixings to take its weight though.

I would suggest a prop of some kind to take its weight before you start taking away its base - the slate which might be load bearing.

As for breaking the slate. Using enough force with a cold chisle I imagine will certainly break it up. Just make sure you have safety goggles because that stuff is dangerously brittel and breaks into shards.

Also be aware of the damage you may cause to other areas of the fire place with extreme vibrations from breaking up the slate as the brick work may be old and jointed with lime mortar (which may be perished)rather then cement and if that's the case then any extreme vibrations and you will see your fire place start to suffer damage.

 

[Joelaw]

Thanks Bondai - The pillars at the front of the fireplace don't seem to be taking much weight and it looks like the weight is supported more by the inner edges and back of the fireplace, on a separate hearth "tongue" which goes back into the fireplace opening - looks like concrete. Just in case though I could leave parts of the hearth under any part of the fireplace where it looks like there might be weight, clear the rest of the area and then get a couple of mates to support either end of the fireplace as I quickly "blitz" those last bits and slide the new hearth in!

I'm worried about damaging the constructional hearth underneath - is slate particularly tough? Is it easy to drill into - I was thinking maybe to drill some connecting holes to help to make removable sections. Any more advice much appreciated.

 

[Bondai]

I'm worried about damaging the constructional hearth underneath - is slate particularly tough? Is it easy to drill into - I was thinking maybe to drill some connecting holes to help to make removable sections. Any more advice much appreciated.

That's not a bad idea - drilling holes into the slate and then pulling it out via some connecting wire of some kind. Because you will probably find that beneath the slate hearth is just compact and very dry mud which will break up with any impacting chisel.

A masonry drill bit will get through the slate - try without the hammer action first though. Have you got some slate you can test on ?

Whatever you do. Just make sure the chimney stack is by no means having any load on what you take out.

My neighbours are just removing their iron surround to make way for a log burner so Ill pester them and tell you my findings - if relevant.

 

[Joelaw]

Cheers Bondai - appreciate it if you could let me know anything else you find out. I've just managed to slip a bit of paper under the pillars of the fireplace that appeared to reach onto the hearth. So clearly the hearth isn't taking any weight at all, so it must be the concrete tongue that's taking the weight with the wall bolts just steadying it - as was meant to be As far as the chimney stack goes there's no worries there - the hearth is just butted up to the wall and not built into it. It's obvious this is a relatively recent addition anyway as although the fireplace is an original victorian one I know slate hearths like this one are a lot more recent.

My main concern was whether I would find the slate too difficult a material to remove. You reckon it shouldn't be too difficult? Is it harder than brick? if so - a lot?

 

[Symptoms]

Joe - if your CI chimney piece (the correct name for your "fireplace") is original to your house it is likely to be mechanically fixed, via a couple of lugs, to the wall (or chimney breast) with screws into wooden plugs - the Victorians often used large nails instead of screws. The wall would then have been plastered - the plaster would cover the fixing lugs making it difficult to see how the fixing was made. Also these CI jobbies often had a couple tongues protruding from the base which sat in pockets in the constructional hearth (the section below your slate) - the purpose of these tongues was to tie the bottom of the chimney piece in place. It sounds that your one doesn't have these tongues 'cos of your paper trick. Anyway, it is likely that your chimney piece will be firmly fixed in place (if original) and you can confidently attack the slate. How?

If, as is likely, your slate stands proud of the adjacent floor level (usually the constructional hearth top is level with the floorboards) your first move is to introduce a couple of levers in the interface between the bottom of the slate and the top of the constructional hearth - hammer the levers in a way, then apply some force to the levers to see if you can 'break' any bond between the 2 hearths and to see how loose the arrangement is. My guess is that they'll come apart easily and you should be able to slip the slate out. If you need to chop into the slate then a cold steel chisel/hammer combo will be fine - go in sideways as slate splits lengthways. A masonary drill willl also help.

If you are tempted to use friends to support the jobbie 'cos it's a bit loose take care for them not to ONLY hold the mantle shelf (if fitted) 'cos this may be a separate section (usually held with a couple of bolts at the rear and these are more often than not rusted to a point of failure). Just imagine the scene ... your mates left holding the mantle shelf whilst the rest of the c/piece falls forward. But I reckon you should be able to proceed safely.

Once the base is cleaned away and dust removed you should be able to slip the new bit in bedded on cement/mortar mix. It doesn't matter if the constructional hearth surface is uneven after removal of old stuff, just level it off with mortar before the new stuff goes in.

 

[Joelaw]

Symptoms - thanks a lot - more great advice. Think I'm ready to go ahead now. here goes....