chris_d
Established Member
Dear Members,
I've been building an extension to my house over the past few months and I'm almost at joist level (intermediate floor). Unfortunately, the joists on the existing building are out of level by 38mm over approx 7.5m. Furthermore, building regulations now dictate that new joists must bear on 'complete masonry units' so blockwork cannot be notched to allow for discrepancies.
I am trying to decide how to lay the next few courses of blocks/coursing bricks to bring the new walls up to joist level. The old and new joists run parallel to each other at 400mm centres and the transition point between old and new will form a single (larger) room. Due to the difference in level of the old joists, I believe that I have four options:
1). Sit new joists in the same plane as the old hence no shimming required to regularise floor planes.
2). Sit new joists at or above the highest point of the old joists and shim above old joists to regularise floor planes;
3). Sit new joists at or below the lowest point of the old joists and shim above new joists to regularise floor planes;
4). Equalise the error, sitting the new joists half-way between the highest and lowest point of the old joists and shim new flooring as appropriate;
Option 1) makes me recoil in disgust as this would severely skew my coursing levels which I would then need to make up for the wall/roof plate in just three courses (215mm / course) and the 38mm discrepancy seems just too big to live with given I usually work to 3.25mils in the day job, hence dismissed! Option 2) has been dismissed to save the hassle of lifting and shimming the existing floor boards. Option 3) is reasonable except that taking the lowest point means that I must cut-down 65mm thermalite coursing bricks to 40mm which is PITA given the 21m course run. Hence I favour option 4) as this can be achieved without the cutting of blocks/coursing bricks but this results in a discrepancy of between 0mm and 19mm over approx 3.75m. Remember that I would have to progressively resolve that discrepancy across joist centres (400mm).
Could anyone with more experience or wisdom please validate or contradict my conclusion?
Now, I freely admit that I have spent way too much time over analysing this and most builders would just pick the nearest convenient coursing height and defer the problem to the floor fitter! However, since I'll be the floor fitter, installing engineered oak, then I'd like to make my life easier with a bit of forethought now!
Thanks in advance,
C
I've been building an extension to my house over the past few months and I'm almost at joist level (intermediate floor). Unfortunately, the joists on the existing building are out of level by 38mm over approx 7.5m. Furthermore, building regulations now dictate that new joists must bear on 'complete masonry units' so blockwork cannot be notched to allow for discrepancies.
I am trying to decide how to lay the next few courses of blocks/coursing bricks to bring the new walls up to joist level. The old and new joists run parallel to each other at 400mm centres and the transition point between old and new will form a single (larger) room. Due to the difference in level of the old joists, I believe that I have four options:
1). Sit new joists in the same plane as the old hence no shimming required to regularise floor planes.
2). Sit new joists at or above the highest point of the old joists and shim above old joists to regularise floor planes;
3). Sit new joists at or below the lowest point of the old joists and shim above new joists to regularise floor planes;
4). Equalise the error, sitting the new joists half-way between the highest and lowest point of the old joists and shim new flooring as appropriate;
Option 1) makes me recoil in disgust as this would severely skew my coursing levels which I would then need to make up for the wall/roof plate in just three courses (215mm / course) and the 38mm discrepancy seems just too big to live with given I usually work to 3.25mils in the day job, hence dismissed! Option 2) has been dismissed to save the hassle of lifting and shimming the existing floor boards. Option 3) is reasonable except that taking the lowest point means that I must cut-down 65mm thermalite coursing bricks to 40mm which is PITA given the 21m course run. Hence I favour option 4) as this can be achieved without the cutting of blocks/coursing bricks but this results in a discrepancy of between 0mm and 19mm over approx 3.75m. Remember that I would have to progressively resolve that discrepancy across joist centres (400mm).
Could anyone with more experience or wisdom please validate or contradict my conclusion?
Now, I freely admit that I have spent way too much time over analysing this and most builders would just pick the nearest convenient coursing height and defer the problem to the floor fitter! However, since I'll be the floor fitter, installing engineered oak, then I'd like to make my life easier with a bit of forethought now!
Thanks in advance,
C