Edwardian Fireplace earth filled

[Mozzy]

Hi All

I have a 1905 house in London, that has damp around the fireplace base. The fire and its base were long gone when we moved in. But on opening up the chimney breast we found the base of the fireplace had a compacted clay base. Even more surprising a foot (300mm) under the clay base, there was a concrete base.
So in effect a concrete an brick trough below the fire and hearth about a foot deep, and filled with clay. Can anyone tell me why. It appears to me the clay is acting like a sponge.

 

[SFK]

Mozzy,
All my 1900's house fireplaces have been brick or wood (using joists) troughs as you describe. Then filled with with soil (often mixed with ash). Over this was the hearth. This is even on second floor (so there is a square of soil in the ceiling above my head).

I have always assumed (so do not know for defiante) that this is a cheap locally avalible (ie using the local soil from the building site) 'filler' that is heat resitant, will also disipate the heat slowly, will not crack like bricks, and will evenly take teh weight from the hearth and the fire above into the floor structure.

I guess yours is clay becuase you are on clay soil in London.

SFK

 

[ree]

Mozzy, have you ever crawled under and examined how the floor joisting frames the hearth?

If the c/breast is on an outside wall is there a small metal cover or door on the outside behind the flue?

Is it the case that you have a front (concrete) hearth but a clay back hearth in the fire place itself?

 

[ree]

SFK, I dont understand what you describe. Can you scan a sketch of what you claim is the first floor hearth construction?

 

[SFK]

Sorry on phone so cannot draw at moment. And unfortnatly do not think I every took a photo.

But as a poor description:
1) My floor joists run accoss teh room into the wall with the fireplace.
2) At the fireplace the joists stop early, and there is a joist sized noggin that goes left to right. This joints the joists on the left and the right of the fireplace. The joists that would have passed under the hearth stop at this noggin joist.
3) This forms a square box with joists on the left and right, a nogin joist on the front and the wall at the back (wall is the chimney).
4) The bottom of this box is the wattle and daub ceiling for the floor below. This surface had a half inch layer of lime mortor on it.
5) The box was then filled will soil.
6) The box was then capped with the Firehearth. Weight of firehearth was supported on joists and rear wall.
7) All seemed to work for last 100years.
Gound floor is same but a brick box that goes into the ground. Note that all these boxes are from floor level going down a foot.

So I think this matches Mozzys "trough below the fire and hearth about a foot deep".

I would presume that Mozzys trough is going into the prehaps wet ground and is absorbing water (mine ground floor trough is dry as surriunduing ground is dry). So I think his question is what does he do to fill the trough now he has removed the Clay. Could he DPM line it and fill with concrete?

SFK

 

[ree]

SFK, but what is actually supporting the weight of the hearth fill? You describe a "wattle and daub" ceiling (could this be lath & plaster?) but ceilings were not built to take any added weight?

If you have a stone or concrete fire (back) hearth how is it supported? And how is your front hearth supported?

Just curious.

 

[SFK]

Yes I meant lath and plaster.

And yes that was all that was holding half of it up.the other half was above the chimney, so the bricks of the ground floor chimney were holding that bit up.

So assuming 70cm wide, 20cm joist (or should that be 30cm) and 30cm from the wall that is 84kg of soil (assuming 2tonnes per m3). That is why I removed them both when I do nd them. But I presume I have one more. The hearth above this was all supported on the joists. So no direct load onto the soil.

Fire back is supported in the chimney.

So I have no idea if this message s normal, but I was suggesting that my ground floor 'trough' was the same as his.

Sfk

 

[Mozzy]

Hi SFK I was just curious if I was the only one with this construction, so obviously not. What surprised me was that under the clay infill there is concrete. So they constructed a concrete and brick trough, then filled it with a sandy clay mix up to just below the hearth level. It covers the entire hearth area about 3 feet square an a foot deep. What sparked this off, is rising damp (neighbours long story). The clay has been absorbing water since a house was built near us. I think previous owners lifted the slate damp course when they fitted a back boiler in the 60s.

 

[Mozzy]

Hi Ree

All the joists stop at the hearth edge. What essentially I have is a trough with a concrete base and brick walls, filled with sandy clay. It seems to me they went to an awful lot of trouble do do this, so the clay infill must have a purpose to do with the long gone coal fire. Regards