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I'm installing a grandfather clock in my house. Problem: my first floor ceiling is 88" high, and the clock is 94" high. I can't modify the clock, so I'll have to modify my house.

The solution is fairly simple: lower a small area of the floor by 7".

Floor area where hole is to be cut

The existing floor is 13/16" x 2 1/2" red oak boards on plank subflooring. The outside blue rectangle shows the edge of the area to be cut and rebuilt (26" x 15"); the inside blue rectangle shows the final footprint of the clock. I've figured out the joists (I'll have to cut a joist and add a doubled header) and the rest of the framing. My final problem is how to finish the edge of the hole.

I'll be cutting the existing flooring in-place, as it would be a can of worms to pull any of it up and then replace it. That means the edges won't be perfect, so I can't just butt new framing boards against the old without leaving ugly gaps. I'd also like to properly define the edge of the hole so that things don't always roll into it. So, I'm thinking to do the equivalent of an overlapping stair nose.

Plan for stair nose overlap

I couldn't find the exact molding I'd need, so I'm planning to cut it from 1" oak stair treads which have a rounded edge and are 12" wide. I'll cut 3" boards from the rounded edge and then shape them further with table saw and sander. There will be a 1/2" x 3/16" tab on the edge of the board to cover the edge of the existing flooring. I'm also thinking to stain the new oak boards to match the cherry wood of the clock; sides of the depression will be 1x pine painted trim white, and the bottom will be the remaining oak tread material finished with polyurethane.

Does this sound like a good plan? Any concerns about that 3/16" thick tab being overly fragile?

EDIT: This question is NOT asking whether it's worth modifying my house to fit this clock. Even if that wasn't clear to me, it would be too opinion-based for this site. Just presume that there's a really good reason for me to do so.

EDIT2: There are good reasons why I'm going into the floor rather than into the ceiling. First, it won't look as good; the focus of the clock is the top, and that will be hidden from view, or at least in a dark nook in the ceiling. Second, I can't tip the clock into place; it must be vertical when the mechanism is installed. That means that there must be room to slide the top case forward and off the clock while it is in place, which means the plaster hole will be substantial. Add the joist modifications and the hole gets even bigger. Final problem: it's a swirl-textured ceiling, so the repairs would be obvious unless I replaced the whole ceiling.

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    I wouldn't make a depression in the floor like this. Seems like a silly idea for just a clock. Store the clock away and bring it out when you have a more suitable place to display it. – Michael Karas Feb 6 '17 at 6:10
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    Commission a professional picture of the clock and hang it on the wall. How will you get the clock into this space on the floor? Nobody has yet figured out how the Easter Islanders moved their statues. Will you be able to move it without hitting the ceiling and breaking the clock? Even if you get it in place, will it overpower the space? If you move it from where it is now to this location, you will throw off the orbits of GPS satellites and cause havoc. The 'Second Coming' may be just around the corner, rendering this unnecessary. Put off this project for a year or so or decade or so. – Jim Stewart Feb 6 '17 at 8:36
  • The clock is 10" deep, and exactly 88" tall WITHOUT the easily-removable top case. So, I can put the foot into the depression, tip it upright, and then install the top case. And, in terms of disrupting GPS satellites, that's what homeowner's insurance is for. – Daniel Griscom Feb 6 '17 at 15:00
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    Is the sunken area large enough to allow opening the case doors? – A. I. Breveleri Feb 6 '17 at 16:34
  • Good question: the bottom of the one door is significantly above the 7" depth of the depression. – Daniel Griscom Feb 6 '17 at 17:30
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Any concerns about that 3/16" thick tab being overly fragile?

My main concern is that you will finish the floor woodwork without incident or problem, install all the new oak molding without chip or blemish, break off at least one of the fragile tabs when moving the clock into place, lose your temper at the whole thing, and smash the clock to matchwood. Leaving an inexplicable useless sunken pit in your floor. With a chipped edge.

At least, that's what I would do.

Avoid the risk by cutting the molding like this: tentative molding cutting suggestion

This gives the profile you specify, but it requires milling the edge of the existing oak flooring in place.

To do this, use your circular saw with a fine crosscut blade. Set the bevel angle to 45° and the depth to about 3/4 in. Use small finish nails to tack a straight edge scrap parallel to the desired cut, at the distance required by the dimension of the saw's foot plate. You can manage almost the entire lengths of the cuts with this method, and finish up with a crosscut hand saw.

Alternately, if you're willing to change your specified profile, you can avoid milling the floor if you build the edge like this: alternate molding cutting suggestion

This gives a much stronger framing effect, but it could be okay since persons will seldom step over it. Also it's more effective at stopping a rolling ball or toy.

The shim should be hardwood for dimensional stability. It keeps the load off the projecting edge when anyone steps on the frame.

  • Nice job editing my diagram! But, how do I precisely cut that bevel in the edge of the existing flooring? Remember that I reeeally don't want to pull up those boards. – Daniel Griscom Feb 6 '17 at 12:17
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    Cut the bevel in the floorboards with a bearing-guided 45 degree chamfer bit in a router. (You needed an excuse to buy more tools, right? That'll make shaping the 'new oak moulding' easier as well. In seriousness, you can find used routers for pretty cheap... Porter Cable 690 motors are pretty bombproof.) – Aloysius Defenestrate Feb 6 '17 at 15:21
  • Good idea to use a router, except that clean results would depend on my being able to cut a clean, linear edge in the floorboards, which again will be problematic. I'm much more interested in your revamped molding profile with shim: thanks. – Daniel Griscom Feb 6 '17 at 21:13
  • Whether you use the circular saw or the bearing-guided router, you do not guide the tool by the newly cut edge of the flooring. You install a temporary straightedge guide -- made, perhaps, from the back edge of the stair tread that you cut the molding from. - Use the smallest finish nails possible to minimize damage to the floor, and to allow reuse of the material. – A. I. Breveleri Feb 7 '17 at 2:02
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    The straight edge guide can be temporarily taped down with double stick tape. Should be much better than trying to nail the piece to the floor. – Michael Karas Feb 7 '17 at 5:07
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the 3/16 x 1/2 overlap tab is a little thin in oak, but it will probably be fine given the other structure you propose.

i will offer this though: you are mental!!!

it seems like your plan is well thought out, but wouldn't it be much easier to just make a hole in the ceiling? then its just plaster and paint? if you ever decide to not have the clock or you move out, its far easier to patch a ceiling than a floor.

if it was me, i would just cut the clock. to remove 8" or so out of a grandfather clock may be impossible (style of cabinet, length of pendulum, etc). however, many times, the casework of the clock is just a hollow carcass with what is essentially a baseboard and legs bolted to the bottom. if you can do what you propose, surely you can build a modified bottom for the clock?

or sell the clock and buy a shorter one???

however, its your clock and house and i am sure you have your reasons.

  • The clock is a family heirloom, so I can't modify it (maim it, really). And, doing the ceiling would be a whole lot uglier, as the top of the clock (its focus) would be disappearing into the plaster. – Daniel Griscom Feb 6 '17 at 4:05
  • Where is the clock right now? – Jim Stewart Feb 6 '17 at 13:23
  • In an apartment; I have to move it elsewhere within the month. – Daniel Griscom Feb 6 '17 at 14:58
  • Another problem with cutting into the ceiling is that I can't tip the clock into place; it must be vertical when the mechanism is installed. That means that there must be room to slide the top case forward and off the clock while it is in place, which means the plaster hole will be substantial. Add the joist modifications and the hole gets even bigger. Final problem: it's a swirl-textured ceiling, so the repairs would be obvious unless I replaced the whole ceiling. – Daniel Griscom Feb 6 '17 at 15:08
  • Figure out what angle you would need to tip the clock sideways to have it fit with the floor as it is now and build a cradle that will hold the clock at that angle. Connect a very soft spring to the bottom of the pendulum or to the movable weight and connect the other end to the inside of the case so that the fixed end of the spring is adjustable in two dimensions. Initially set the spring so that when the pendulum is at rest the spring is perpendicular to it and adjust the spring in and out so that the pendulum hangs parallel to the long axis of the clock. Great conversation piece! – Jim Stewart Feb 6 '17 at 16:47
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corner edge molding & sistered FJ

If the point of the bullnose is to cover untidy saw marks then all that should be needed is outside corner molding (which comes is several sizes).

Also, since a joist is being cut, it should be replaced with sistered 2x10's (2x8's min.) and reinforced with metal joist hangars and corner braces.

Don't forget, the clock will be sitting on a new (lowered floor) which will also need to be supported. You'll have to create FJs for that, too.

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