What distance are these 245mm by 45mm joists spanning and how far apart are they?
Reduce joist height
- Thread starter burts
- Start date
D
Deleted member 174758
Notwithstanding the discussion on whether the joists would have sufficient strength afterwards, assuming they will, then...
From my simple perspective the easiest way to do this job will be to add an enlarged fence plate to the rip fence of a saw (so it can be used safely on its' side - a piece of 18mm ply 6 x 2in screwed on will do) then plunge the saw in, make the cut and finish with a hand saw. Then repeat. And repeat. And repeat. Basically two tools - no need for planer or myltitool, even, just a hand saw and a circular with a 60mm depth of cut. My only caution on this is that drop cutting like this is not for the faint of heart - you need to be wary of the potential of the saw to kick back. That said I've just dine something similar this week - cut olaway part of a rebated 100 yearvold door lining to take a new fire rated door frame. Worked out well
The saw will need to be fairly light and compact - for example something like my brushless Makita 165mm saw (DHS680) could do the job, but a physically larger saw such as the 190mm DHS782 would be awkward to handle
Planing won't work - you need to accomodate the front and rear soles which would result in a concave joist top
Recip saw wouldn't fit
Jigsaw or multitool would be slow and probably produce a very variable surface (i.e. not perpendicular to the sides of the joists)
Handsaw? Strictly for hair shirts, surely,
but also too long to get in there, and In any case most handcsaws these days are terrible forvl ripping (they are
crosscut saws)
Battens? You'll end up with a dogs dinner of a floor which I suspect will always move(and creak, be draughty) and have loads of joints to telegraph through. I suspect that the floor might eventually need to be skinned with 5.5mm.plywood to get a smooth/non-moving surface for finishes such as LVT, laminate, etc
Routing I just think would be a hugely time consuming task, not to mention messy and noisy, way longer than sawing (BTW the "centring device" is a longer pair of home made silver steel fence rods and a second fence, which can be as simple a a lump of 3 x 2in softwood with two holes drilled through it and a couple of screws - that's what I sometimes use for floor box ironmongery)
From my simple perspective the easiest way to do this job will be to add an enlarged fence plate to the rip fence of a saw (so it can be used safely on its' side - a piece of 18mm ply 6 x 2in screwed on will do) then plunge the saw in, make the cut and finish with a hand saw. Then repeat. And repeat. And repeat. Basically two tools - no need for planer or myltitool, even, just a hand saw and a circular with a 60mm depth of cut. My only caution on this is that drop cutting like this is not for the faint of heart - you need to be wary of the potential of the saw to kick back. That said I've just dine something similar this week - cut olaway part of a rebated 100 yearvold door lining to take a new fire rated door frame. Worked out well
The saw will need to be fairly light and compact - for example something like my brushless Makita 165mm saw (DHS680) could do the job, but a physically larger saw such as the 190mm DHS782 would be awkward to handle
Planing won't work - you need to accomodate the front and rear soles which would result in a concave joist top
Recip saw wouldn't fit
Jigsaw or multitool would be slow and probably produce a very variable surface (i.e. not perpendicular to the sides of the joists)
Handsaw? Strictly for hair shirts, surely,
but also too long to get in there, and In any case most handcsaws these days are terrible forvl ripping (they are
crosscut saws)
Battens? You'll end up with a dogs dinner of a floor which I suspect will always move(and creak, be draughty) and have loads of joints to telegraph through. I suspect that the floor might eventually need to be skinned with 5.5mm.plywood to get a smooth/non-moving surface for finishes such as LVT, laminate, etc
Routing I just think would be a hugely time consuming task, not to mention messy and noisy, way longer than sawing (BTW the "centring device" is a longer pair of home made silver steel fence rods and a second fence, which can be as simple a a lump of 3 x 2in softwood with two holes drilled through it and a couple of screws - that's what I sometimes use for floor box ironmongery)
Last edited by a moderator:
What happens when you get to the noggins, assuming they're the same depth as the joists?
450 centres and they span 3.9m
I believe 47 x 220 alows a span of 4.35
D
Deleted member 174758
Any solid strutting or herringbone strutting needs to be knocked out first, then replaced afterwards. Not difficult with solid strutting - just takes a hammer and a bit o' welly to knock it out, the replacement strutting might be best made new. Frankly, I can't see it being possible to replace herringbone strutting like for like if the ceiling is already installed - you'd probably need to go to solid strutting instead, which can be installed with existing ceilings in place. If there are pipes or wires in the floor, though, it would be a bit more awkward, but it's easier to deal with those if you have the majority of the base plate of the saw to the top - for which a left hand blade saw seems to make more sense. But you may also need a multitool or jigsaw for those cases
Last edited by a moderator:
Just thinking aloud here, in my customary amateur random way - I find myself wondering whether lowering the joists, then re-boarding and skimming the ceiling below might be less work than taking the tops off them...
D
Deleted member 174758
Not just you. In my trade way I was thinking the same, and @robinbanks mentioned notching the undersides of the joists but...
Which sort of limits the approach to dealing with this...
The joists can’t be lowered. They sit on block walls and ripping down the ceiling def isn’t worth it.
I don’t mind how long it takes upstairs as the room isn’t in use anyway.
Some of the noggins might have board screwed to them underneath. I’m going to have to assess the worthwhile mess of it all.
If I was doing it I would use a biscuit jointer, they go about 25mm deep and the fence can be set almost 30mm
they are designed for plunge cutting not ripping, but I’ve done a few times myself but I can’t recommend on a public forum for somebody to use a tool not for its intended purpose.
Alternatively you could use a groover for a router - they can cut 22mm deep, so running both sides would do it
Groover 60
either option would get you close to the wall
If I was doing it I would use a biscuit jointer, they go about 25mm deep and the fence can be set almost 30mm
they are designed for plunge cutting not ripping, but I’ve done a few times myself but I can’t recommend on a public forum for somebody to use a tool not for its intended purpose.
Alternatively you could use a groover for a router - they can cut 22mm deep, so running both sides would do it
Groover 60
www.wealdentool.com
either option would get you close to the wa
D
Deleted member 174758
Normally when boarding ceilings you screw to the joist lines, not the solid strutting. When you have a board balanced on your head with maybe the other end supported on a tee it's kind of difficult (often impossible) to hit a piece of solid strutting which runs at right angles to the joists - it's far, far easier to aim for the joists, because you can see where they are located down one edge of the board, and on the other edge you'll either have pencil marks on the wall (first row) or a nice row of visible screw heads and you can assess where the joist line us quite easily. It would waste a lot of time messing about measuring where strutting was so you could screw into it.
If you'd ever seen a pro installing a ceiling, or even installed one yourself, this would be obvious to you. You might conceivably get a few screws where a piece of solid strutting is visible on a board edge and could be screwed into, but I can't see a pro doing that very often, either
Last edited by a moderator:
A biscuit jointer has a fence that swivels from vertical down to 90 degrees and it winds up and down.
when the fence is set at 90 degrees you lay that on the top of your work and plunge in - height of fence sets distance between blade and fence
Yea cause you wouldn't fix the ceiling to a bit of strutting because you're not a professional or on the bonkers off chance you might need to remove them later. Classic J&K. 