Discussion
As part of the renovation on our house we have now started to look at the old part of the house. Ultimately we want to lower the existing floor to increase the room height which is currently about 1.7m. The house is built into a slope and is old stone solid wall construction. The existing floor needs digging up anyway as it currently doesn't have any insulation or membrane. I'm getting the necessary advice from a structural engineer who is coming out to inspect some trial pits but with my rough estimates the current foundation level is not far off where we want the finished floor level to give us a more reasonable 2.1m room height. This would mean digging below current foundation level to get the needed floor makeup in (Insulation, membrane slab etc.)
The house doesn't suffer from any subsidence but I'm just starting to wonder if it's all worth it. It's the guest room and ensuite which will be impacted so maybe its nice to keep it nice and cosy. We would however loose the patio doors which we had planned to install, which is a shame as with it's own entrance we had considered AirB&B.
My understanding is it's very time intensive but not hugely complicated. I've read a bit about underpinning causing issues with insurance but surely that applies to cases where it's needed for subsidence etc.
I will wait to see what the structural engineer has to say but has anyone gone through anything similar?
The house doesn't suffer from any subsidence but I'm just starting to wonder if it's all worth it. It's the guest room and ensuite which will be impacted so maybe its nice to keep it nice and cosy. We would however loose the patio doors which we had planned to install, which is a shame as with it's own entrance we had considered AirB&B.
My understanding is it's very time intensive but not hugely complicated. I've read a bit about underpinning causing issues with insurance but surely that applies to cases where it's needed for subsidence etc.
I will wait to see what the structural engineer has to say but has anyone gone through anything similar?
Traditional mass concrete underpinning is a low tech process and can be handled by any reasonably competent builder but it helps if they have relevant previous experience - your SE will provide a scheme showing the bay layout and sequence and a method statement.
It's essentially a case of hard graft, muck away and then concrete in so it's not especially difficult.
Ultimately it will be a balance between cost and the utility derived from the work. However if it's a large space I would say even 2.1m could feel a bit oppressive.
It should have no effect on your insurance given it's not related to a subsidence issue.
It's essentially a case of hard graft, muck away and then concrete in so it's not especially difficult.
Ultimately it will be a balance between cost and the utility derived from the work. However if it's a large space I would say even 2.1m could feel a bit oppressive.
It should have no effect on your insurance given it's not related to a subsidence issue.
tperry said:
As part of the renovation on our house we have now started to look at the old part of the house. Ultimately we want to lower the existing floor to increase the room height which is currently about 1.7m. The house is built into a slope and is old stone solid wall construction. The existing floor needs digging up anyway as it currently doesn't have any insulation or membrane.?
How much of the overall floor plan is getting dug up, having been through it with our build, the phones calls of 'Hi, just dug up the old foundation, it looks worse than we thought......' got to a point where it just became comical. Demolition and rebuild would have been faster and cheaper for us in hindsight. For the next build we do, I'll 100% be going down the demolition/rebuild process, or just an empty bit of land to start off with.
1.7m is a very low ceiling.
An extra 400mm clear span for the wall is significant for design and may require a stronger wall. (Also depends on the horizontal span and might be satisfied with a single external pier, or it might be OK as it is.)
Built into the hillside - does that mean that the wall also forms a retaining wall? If so the wall may be thicker/stronger anyway and things like a French drain to remove water pressure - or just dig out and have a secondary wall - would help.
These project go wrong (collapse) when people do the whole room at once rather than a scheduled 1m at a time approach.
I would dig down and install a new foundation at lower level then fill in to the underside of the wall to avoid underpinning. To do this you might need to remove the existing foundation (which might be impractical) or there might not be an existing foundation - likely to be a spread footing but some footings spread by 3" on each side and some spread by a foot on each side. What have your trial holes revealed?
An extra 400mm clear span for the wall is significant for design and may require a stronger wall. (Also depends on the horizontal span and might be satisfied with a single external pier, or it might be OK as it is.)
Built into the hillside - does that mean that the wall also forms a retaining wall? If so the wall may be thicker/stronger anyway and things like a French drain to remove water pressure - or just dig out and have a secondary wall - would help.
These project go wrong (collapse) when people do the whole room at once rather than a scheduled 1m at a time approach.
I would dig down and install a new foundation at lower level then fill in to the underside of the wall to avoid underpinning. To do this you might need to remove the existing foundation (which might be impractical) or there might not be an existing foundation - likely to be a spread footing but some footings spread by 3" on each side and some spread by a foot on each side. What have your trial holes revealed?
Thanks for the responses. This is the original plan we have.
The purple lines in the bed room are where we have the current low ceiling. The corridor/ensuite/utility are currently 1900mm so i'm pretty confident this can be lowered without anything structural (I will verify this obviously). The patio doors would feed out to a patio which means adding a retaining wall a bit further back from the gable end.
The purple lines in the bed room are where we have the current low ceiling. The corridor/ensuite/utility are currently 1900mm so i'm pretty confident this can be lowered without anything structural (I will verify this obviously). The patio doors would feed out to a patio which means adding a retaining wall a bit further back from the gable end.
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