Hi All,
I am in the process of putting a fireplace back in and found the soil / rubble to make the original constructional hearth is damp (photo attached).
The joist end on the left has some rot on the back corner going back an inch or so, it is only a small area and I dont believe this will be a problem as long as it can be stopped from spread further. There is no mould on it.
The brick on which this joist sits was very damp, there is no slate between the brick and joist.
I have dug out all the soil at the front which was below a concrete cap. Once that was removed there was a flat layer of clay at which I stopped digging. Inside the chimney recess are some old quarry tiles with the same damp soil and rubble below. I will almost certainly remove these quarries and dig out the damp soil and rubble there too.
I believe the damp is most likely coming in through the external wall behind the chimney. There is a concreate path against that wall on the outside above the level of the damp found here.
So aside from digging out the rest of the soil I am not sure what I should do next.
1) I had considered using DPC cream on the back wall but am not convinced that will do much as these the lower courses of bricks are blow the outside ground level.
2) I need to backfill the void to rebuild the hearth, I am wondering if course non permiable gravel would prevent the damp spreading the way it did through the soil?
3) I am not convinced about using a damp proof membrane around the backfill material, i am concerned that any moisture that does end up in there will not be able to escape, and as I plan to use this fire once installed do not think I can run a plastic membrane high enough up the wall without it becoming a problem later on.
4) I could add another line of bricks across the front of the hearth and only backfill the rear portion in the chimney recess and suspend the front part of the hearth to allow better air flow around the joist ends
If anyone could comment on the above or offer any other suggestions I would be most grateful!
I am in the process of putting a fireplace back in and found the soil / rubble to make the original constructional hearth is damp (photo attached).
The joist end on the left has some rot on the back corner going back an inch or so, it is only a small area and I dont believe this will be a problem as long as it can be stopped from spread further. There is no mould on it.
The brick on which this joist sits was very damp, there is no slate between the brick and joist.
I have dug out all the soil at the front which was below a concrete cap. Once that was removed there was a flat layer of clay at which I stopped digging. Inside the chimney recess are some old quarry tiles with the same damp soil and rubble below. I will almost certainly remove these quarries and dig out the damp soil and rubble there too.
I believe the damp is most likely coming in through the external wall behind the chimney. There is a concreate path against that wall on the outside above the level of the damp found here.
So aside from digging out the rest of the soil I am not sure what I should do next.
1) I had considered using DPC cream on the back wall but am not convinced that will do much as these the lower courses of bricks are blow the outside ground level.
2) I need to backfill the void to rebuild the hearth, I am wondering if course non permiable gravel would prevent the damp spreading the way it did through the soil?
3) I am not convinced about using a damp proof membrane around the backfill material, i am concerned that any moisture that does end up in there will not be able to escape, and as I plan to use this fire once installed do not think I can run a plastic membrane high enough up the wall without it becoming a problem later on.
4) I could add another line of bricks across the front of the hearth and only backfill the rear portion in the chimney recess and suspend the front part of the hearth to allow better air flow around the joist ends
If anyone could comment on the above or offer any other suggestions I would be most grateful!
