Tuesday, 5 January 2016

Installing a slate hearth

Having installed the reclaimed oak beam as a fireplace lintel/mantelshelf successfully, it was time to turn our attention to the remainder of the fireplace.

We've already chosen our stove; the chimney flue liner (long-lasting 904 grade, both to allow for longevity and the fact that Muz is a pyromaniac) was put in as soon as the chimney pots were installed; and the register plate and flue liner adapter (we put a six-inch flue in the chimney, and the stove output is 5-inch - future proofing in case we ever get a stove with a bigger output) are now in too, so we pretty much just needed to put in a hearth and then the stove can be installed.

Our time capsule now lives in here.
The brick 'step' at the back had to be lowered by 25mm
so the new hearth would be level with the floor in the room.
I spent some time researching on the brilliant stovefittersmanual.co.uk website to find UK hearth regulations. Having done that, and established what size we needed, we were ready.

We decided we'd like to use a single slab of slate, having seen some at the same reclamation yard that we bought our beam from. Unfortunately when we rocked up with our measurements, the largest slate they had was still 80mm too narrow so we skulked back home with our tails between our legs, and started Googling for a Plan B.
Then my mum came up with a genius idea, by suggesting that we try the same place that had made our house sign. Replacing the rubbishy wooden house sign with a nice coordinated sandstone version was something we did back in the summer, courtesy of an excellent stonemason called Thomas - who we then completely forgot about. Doh.

Sharp, square-edged (not chamfered) and cut to exactly
the same width as the mantel above it. The devil
is in the detail, apparently.
Off we went and yes, they could do what we wanted for not a lot more than the slate from the reclamation yard would have been. We ordered it, expecting to get it early in the new year. But on the 23rd December, we got a phone call - it was ready to pick up if we wanted it before Christmas? Absolutely we did, so one slow and careful car journey later and the hearth was propped up against a wall waiting for it's final resting place.

And what better time to install it than the random bit in between Christmas and New Year? Especially when a handy bank holiday Monday was available. Unfortunately Muz came back from his family Christmas with man-flu and was forced to stay in bed. 

So my dad, aka Terminator Trevor, came round and the two of us got cracking while Muz took copious amounts of Beechams and occasionally appeared looking sorry for himself before heading back to bed (EDIT: I evaded the Grim Reaper by a mere whisker - Muz).

We'd already filled in the void under the hearth with a combination of our time capsule, old bricks, gravel and sand. Before we started setting the hearth stone in place, we first lifted a few of the quarry tiles from directly in front of the chimney breast, where the edge of the new hearth would rest. One tile was badly broken and some more had sunk quite significantly in to what appears to be a (surprising) thin lime bed on top of sand, so we swapped the broken one for a different tile, and put additional sand underneath the others to level them up.

Glazed tile chunk
We also needed to chip away a small, slightly raised, area where the previous hearth had been, in order to get our new level. This turned out to be a small fragment of old glazed tile - we guess from around about 1900.

I spent some time Frogtaping (like masking tape, but better) the edges of the hearth slab that would be exposed, and then covering the remainder of the top surface with newspaper, to save any splashes of mortar discolouring the stone.

To set the hearth in place, we then made a lime mortar mix, using 2 parts sharp sand, 1-and-a-bit part NHL3.5 lime, plus water, having read this interesting article around commonly used 1:3 mixes and that fact that hydrated volumes change the ratio.

Moisture content beneath ground level inside the fireplace came in at 100%+, so the lime mortar was laid thick to
give a good level, solid grounding and plenty of breatheable material through which moisture will naturally wick. This
will also be helped by a 20mm lime mortar-pointed gap between the bricks and slate when it's in.

Yet another tea break for Terminator Trevor

Using some narrow pieces of wood to set the correct level, we spread the mortar in, and leveled it off. 

We then removed the wood levels, filled in the void left behind by those, and then man/womanhandled the mammoth slate into place. A bit of pointing around the edges and we were done!

Now to wait a week or so until it's gone off and the stove can go in, although we need to paint the register plate and possibly re-point some of the mortar first.

Ta daa...

The thick lime bed should help the naturally damp materials beneath, especially towards the back, breathe

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