Hello again!
I am considering how best to install a flood defence mechanism into our 17th Century farmhouse. We are right on the edge of the area that floods and at the height of the recent flooding (last 5 years) we have clean floodwater reach our house for about 2-3 days. In other words we have had 5 days of flooding in the last 10 years when flooding has been at its worst in living memory! Neighbours further down the road, lying lower and closer to the stream that floods, have had sump & pump systems installed into their proprties, with great success. I had hoped to have a sump & pump system working a bit like an internal equivalent of a french drain, with a drainage channel inside the walls, skirting around the inside perimeter, which then drained into 2 sumps which would pump out the water. The very good company that has just given us a quote on this work has sprung a rather nasty suprise, however. All of this would need to be laid on top of a concrete slab as, without this, the water ingress would be too fast for the pumps to be able to match. What we need to create is a situation where the house acts as a boat and the sump as a bilge pump. At the moment we have a bottomless boat!
My difficulty is that I am totally against having a concrete slab in our house and suspect that the ongoing problems that this slab would cause in pushing damp up the walls will be greater than the problems that an occasional few days of a few millimetres of flooding will create. The design is such that there would be a space above the slab below the floor so there would be no damp build up there, but surely the water under the slab would be forced out to the walls.
I had suggested that we could use a limecrete slab, but have been assured that this would become waterlogged and not provide the necessary water resistance to allow the ingress to be slowed enough to make pumping out successful.
I should point out that we are not panning on touching any original flooring as most of our floor has already been blessed with an old shallow concrete slab (1930s I think) which I was hoping to remove, some other areas have a newish suspended wooden floor which isn't the best idea in a flood risk area. The house originally had solid flooring, probably flagstones, as one small area still has flagstones which will be untouched of course! We had also originally hoped to install underfloor heating (about which I know very little, other than that it provides the good sort of heating for an old house) and assume that this might have to be laid on something like limecrete. It might be that this sways which sort of base material we have as UFH surely can't be laid on bare earth!
My proposed in between solution is to create the drain, sump and pump as intended but to do without a slab or use a limecrete one (on which the UFH might sit if it needs a base) and hope that it acts as enough of a barrier to the water to allow the pumps to keep up. I ought perhaps to add a geomembrane on top of the earth to filter any fine soil which might otherwise get in the drain and clog the pumps. This solution won't count as a flood defence mechanism though - rather it was called flood alleviation by the company that I discussed it with. I get the feeling that they're not particularly willing to install it, though, so I might be on my own. They also said that there was a high chance that, without a concrete slab providing water resistance, no system would work.
Whilst it is very tempting to say that we can do without flood mitigation measures, as the house has managed for 400 years or so without, the final spanner in the works is that our planning permission was granted subject to our installing flood mitigation measures as outlined in the flood risk assessment. At that point in time we had indicated that we would use a sump & pump method as I didn't know about the necessity of a concrete slab!
Please help with any ideas that you can as to how we might solve this. I rather hope that the in between measure outlined above could be adopted if we ask our CO for flexibilty in reaching compliance with the lbc condititions as we are so anxious to avoid a concrete slab. Ought I to forget my concerns about concrete, though?
I am considering how best to install a flood defence mechanism into our 17th Century farmhouse. We are right on the edge of the area that floods and at the height of the recent flooding (last 5 years) we have clean floodwater reach our house for about 2-3 days. In other words we have had 5 days of flooding in the last 10 years when flooding has been at its worst in living memory! Neighbours further down the road, lying lower and closer to the stream that floods, have had sump & pump systems installed into their proprties, with great success. I had hoped to have a sump & pump system working a bit like an internal equivalent of a french drain, with a drainage channel inside the walls, skirting around the inside perimeter, which then drained into 2 sumps which would pump out the water. The very good company that has just given us a quote on this work has sprung a rather nasty suprise, however. All of this would need to be laid on top of a concrete slab as, without this, the water ingress would be too fast for the pumps to be able to match. What we need to create is a situation where the house acts as a boat and the sump as a bilge pump. At the moment we have a bottomless boat!
My difficulty is that I am totally against having a concrete slab in our house and suspect that the ongoing problems that this slab would cause in pushing damp up the walls will be greater than the problems that an occasional few days of a few millimetres of flooding will create. The design is such that there would be a space above the slab below the floor so there would be no damp build up there, but surely the water under the slab would be forced out to the walls.
I had suggested that we could use a limecrete slab, but have been assured that this would become waterlogged and not provide the necessary water resistance to allow the ingress to be slowed enough to make pumping out successful.
I should point out that we are not panning on touching any original flooring as most of our floor has already been blessed with an old shallow concrete slab (1930s I think) which I was hoping to remove, some other areas have a newish suspended wooden floor which isn't the best idea in a flood risk area. The house originally had solid flooring, probably flagstones, as one small area still has flagstones which will be untouched of course! We had also originally hoped to install underfloor heating (about which I know very little, other than that it provides the good sort of heating for an old house) and assume that this might have to be laid on something like limecrete. It might be that this sways which sort of base material we have as UFH surely can't be laid on bare earth!
My proposed in between solution is to create the drain, sump and pump as intended but to do without a slab or use a limecrete one (on which the UFH might sit if it needs a base) and hope that it acts as enough of a barrier to the water to allow the pumps to keep up. I ought perhaps to add a geomembrane on top of the earth to filter any fine soil which might otherwise get in the drain and clog the pumps. This solution won't count as a flood defence mechanism though - rather it was called flood alleviation by the company that I discussed it with. I get the feeling that they're not particularly willing to install it, though, so I might be on my own. They also said that there was a high chance that, without a concrete slab providing water resistance, no system would work.
Whilst it is very tempting to say that we can do without flood mitigation measures, as the house has managed for 400 years or so without, the final spanner in the works is that our planning permission was granted subject to our installing flood mitigation measures as outlined in the flood risk assessment. At that point in time we had indicated that we would use a sump & pump method as I didn't know about the necessity of a concrete slab!
Please help with any ideas that you can as to how we might solve this. I rather hope that the in between measure outlined above could be adopted if we ask our CO for flexibilty in reaching compliance with the lbc condititions as we are so anxious to avoid a concrete slab. Ought I to forget my concerns about concrete, though?
