Cornishcottage_
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Hi is this original or a later addition? Does it need to come off?
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Cubist
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Looks to me like someone has 'capped' the foundation stones with concrete to meet the render above. Looks like Portland cement rather than lime and could have been an attempt to prevent water run-off from the face of the house eroding lime mortar used in the original foundation and/or the stone it was built with. Question is, is there any evidence of damp inside the house?
Cornishcottage_
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Hi thanks for response. Yes there is. Started with lowering ground level and discovered this. Do l leave for the minute and when have lime render applied after removing the cement get the line specialist to reinstate a protective layer for the foundations?
Are we really talking foundation stones here, in which case why are they on show above ground? Or is this a stone plinth for a timber frame? Hard to tell from the close up image what the vertical plane looks like from render down, do the stones protrude, what is the render and what is the construction under it?
You say lowering ground levels, where? I’m presuming outside but I’d guess the concrete slabs there up to the house aren’t helping with the damp you mention… I’d be lifting these first to get at least 6 inches lower out than in. Then remove the cement render on the wall depending on the issues. But cautiously, as removal can damage the underlying softer structure and in some cases, like cob, the cement render has taken in a structural role itself… where is the damp and is this the reason for what your doing? more context and details before you can make the right decision…
Cornishcottage_
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Hi thanks for your response. The other side of the house is having its ground levels reduced where l have damp issues. The photograph is of the other side l was exploring what was behind the concrete and found the foundations. The house is 1904 brick, rendered in cement. Do l remove the cement from the foundations and heighten this side? I am having the cement rendering removed and replaced with lime.
So on the cusp of cavity walls and DPC then - is it constructed this way, or still solid brick?
If it’s cavity, then your damp issue is probably less the render on the entire wall, more the lower section where the dpc may have been bridged by the render or the ground levels themselves if high enough.
If it’s a solid wall, then your lime render approach is right - but it’s an expensive and slow job to do properly, so if there are no damp issues then maybe worth focussing attention elsewhere.
Can’t really comment on the ‘foundations’ as for a house of that age I wouldn’t expect them to be visible above ground. So either we’re talking about something else, or the external levels have previously been excessively lowered to expose them. What’s the floor height internally compared to outside/foundations?
Cornishcottage_
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Hi
It’s solid walls. The internal ground level is higher at the front of the house than externally. It must of been reduced at some point?
At the back it is lower. We have dug down removed cement and patio slabs. Planning to put in French drains and then gravel.
Just wondering then from what you are saying if at the front to remove the cement encasing the foundations and heighten the ground and installing a drain?
One wall is badly cracked on the rendering and suffers damp. Thinking of replacing the cement for lime and do the rest of the house after saving up?
It’s solid walls. The internal ground level is higher at the front of the house than externally. It must of been reduced at some point?
At the back it is lower. We have dug down removed cement and patio slabs. Planning to put in French drains and then gravel.
Just wondering then from what you are saying if at the front to remove the cement encasing the foundations and heighten the ground and installing a drain?
One wall is badly cracked on the rendering and suffers damp. Thinking of replacing the cement for lime and do the rest of the house after saving up?
Cubist
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I agree that stone plinths were often used as foundations to establish levels for timber frame buildings but they were also used for the same purpose for brick structures. Depending on the topology of the site some sections of the plinth may not have been completely buried after completion of the build. It appears to me that the cap was installed before the render to provide a sharp delineation/transition between the render and the level of the ground. DPCs became mandatory in London in around 1875 and their use became widespread in the following years, so theres a chance your house may have one. If so, I would expect it to appear above the capping. and it may be that the render is bridging it. Cracks in the render will obviously allow water to penetrate and, unless this can escape to the exterior, it will be causing some of the damp indoors. It would be an idea to do what you can to repair the damaged render to prevent further ingress and commit to full replacement later.
On balance I would be reluctant to remove the capping. You don't need to do this merely to open up the trenches for French drains or lower the ground levels.
On balance I would be reluctant to remove the capping. You don't need to do this merely to open up the trenches for French drains or lower the ground levels.
Cornishcottage_
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Thank you much appreciated.
whatever it's purpose, it looks like you have a soaking wet wall underneath - if you can protect it from the rain it may well start to dry out and change colour. If so, I would be taking the rest off ASAP , probably a quick and easy job with an SDS drill. or a day's hard labour with a chisel
Zebra
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If the capping were removed now, then whatever it is covering (which we are referring to as the foundations but we're not sure that those are the foundations - it all looks quite scrappy and loose) may then take on even more water from rainfall, which is then stuck behind the cement render. I would leave alone for now and concentrate efforts elsewhere as Kearn says. I would make a decision about that capping once the render is off the walls, and once the DPC (if there is one) has been located. It may do no harm to leave it.
malcolm
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The care point is going to be the flat surface at the top of the plinth. That would benefit from being waterproof with a slope of at least 8 degrees to stop rainwater from settling on top and making it's way in.
It it were me I would remove the horrid concrete from the plinth and repoint with lime mortar if necessary so at least some water can start evaporating away from the wall.
For a sloping capping - a weak mix of concrete (portland cement) would probably be best for now as whatever you do will need to be done again when the render is removed. For later maybe it could be made more pretty with a tile or slate capping or lead but the sloping part does need to be resilient and fairly waterproof.
It it were me I would remove the horrid concrete from the plinth and repoint with lime mortar if necessary so at least some water can start evaporating away from the wall.
For a sloping capping - a weak mix of concrete (portland cement) would probably be best for now as whatever you do will need to be done again when the render is removed. For later maybe it could be made more pretty with a tile or slate capping or lead but the sloping part does need to be resilient and fairly waterproof.
Cornishcottage_
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Thanks much appreciated. Will get it covered in the meantime hoping the cement rendering is coming off and lime applied soon….. It has been dry this week and already looking better 