Floor strengthening: is this a really stupid idea?

I've got this idea about how to get over a problem with my upstairs floor, and I'm sort of hopeful that it might not be as stupid as I think it probably is.
I have a downstairs space, about 8m x 4.5m. The floor above it is constructed from 4"x2" timbers (17" centres) hung from the walls and a central oak beam. The oak beam (dating from about 1650) spans the 8.5m and is supported at half way. The ceiling is just the upstairs floorboards.
This arrangement is unsatisfactory for several reasons, the most annoying of which is the way the 4x2s are hung off the oak beam - it really is atrocious to look at! I had resigned myself to ripping the whole lot out and putting in a new floor. I don't want to box in the beam.
Then it occurred to me that I could just put another floor on top of the existing one. I could mirror all the joists and glue and screw both floors together. This would allow me to improve the aesthetics of the beam/joist join. Then I would get a less bouncy floor, have room to run services and save lots of money and time. If the wife objects to the floorboard look of the ceiling, I stick something onto it even if it's only paper.
Can anyone spot the fatal flaw?
T
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In an earlier contribution to this discussion,

I don't understand!
Surely the beam/joist junctions are only visible from *below*? So how will building something on *top* improve the appearance of that?
Adding more joists is unlikely to increase the overall bending stiffness. Even if glued and screwed, it's still not the same as a single taller joist. And, adding more weight may actually *increase* the springiness.
By how much would the floor be raised? Have you got sufficient headroom to permit this? What about the floors of adjacent rooms, still at the original level? [You will need a step onto the new floor. Is that a problem?]
--
Cheers,
Roger
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Roger Mills wrote:

Mmm. My thoughts exactly.

If they are done on top of and firtmly fixed to, existing, they will indeed increase stiffness.

I am thinking that the OP should rip teh old out, get some 7x4 oak, and notch them over the spine beam.
Then nail batten a cvouile of inches from the base of thse and board over - that leasve cavities for wioring, and te oak vabses will be expose..
then - what I did here - not bad - was to lay insulation board over and then plate the top storey floor with chip. Would have used real wood if hadn't been going for carpet throughout.
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I had hoped as much.

That's what I should do, and it would look fantastic.
Regards
T
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snipped-for-privacy@gmail.com wrote:

God. sorry about the typing there. At least you managed to cotton on..
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I would have to support the existing joists from above - probably with hangers, rather than from below by a length of 4x2 nailed onto the side of the beam.

I thought doubling the height tripled the stiffness. I'd be happy with 1.5 times the stiffness. The floor isn't really that bouncy. I would put the new joists in the walls, and supplement the beam with 4x 4x2s on top of it. ( actually, I could probably squeeze in 4 x 6x2s as the top of the beam is below the top of the joists.)

The floor would be raised by about 4.5". I've got plenty of headroom, in fact I've got a much older ceiling about 16" above my current ceiling. Between this part of the house and the rest, there is at present two steps - one 8" and one 4". So, should I go ahead with this, there will still be two steps - one 3.5" and one 4".
I know that it's all a bit unorthodox, but this whole place is unorthodox.
Regards
T
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snipped-for-privacy@gmail.com wrote:

Ah. So thats the 'ugliness'. Th 4x2 nailed to the beam..

Sounds Ok tho I can;'t quite picture it.

All the more fun.
I'd just buold a new floor completely to modern standard well above the existing one, and prettify what's underneath,

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It's hideous, and gets worse every time I look at it.

It's too horrible even to imagine! Basically the old beam is approx. 8"x8". The 4x2s support nailed to it are about 3" from the top of the beam, so the joists that sit on the support project above the level of the beam. I told you it was nasty. My guess is that this was done in the 1930s when the then residents had different priorities from today.

I'm afraid the fun aspect of this renovation is dwindling; just as is my wallet and my wife's patience!

That's probably an even better idea. It will be hard to get it past the wife, as although we have plenty of ceiling height (far more upstairs than down), the windows are quite low. If I went up more than about 5" in total, she'd definitely notice and complain!
Regards
T
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snipped-for-privacy@gmail.com wrote:

Well how about 7x3s notched 3" over the main beam..that gives you 4" above and 3" below..leavening space to both put in a plasterboard ceiling underneath, and screw some 6x2 oak underneath to make it look pretty.
Plenty of room for cables you get a nice flat floor above, and underneath its all either flat plain plaster, or plaster with fake (non structural ort not VERY structural) oak beams. The alternative is 10x6 oaks and battens and a bitch of a pastering job.
Really I'd take the lot down and build a new ceiling/floor with a void.
It goes quite fast..and its not THAT expensive either.

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On 20 Dec, 11:22, snipped-for-privacy@gmail.com wrote:

Dear T Reading your post rather frightened and slightly saddened me. This is a 1650s building and even if it is not listed should be respected as such. As I now understand it you have two problems 1) the desirability (possibly need) to increase stiffenss 2) more importantly to eliminate your annoyance at the 4" by 2" connections (battens supporting what I suspect are joists pulling out of a perfectly good mortice and tenon joint due to the original walls having pulled apart and pulled the joist out of the joint
If this is correct you need to consider each separately
Lets deal with stiffness first
options.... determine if it is the main beam that is not stiff enough or the 4 x 2s or both or the connections
If the main beam you can put a T beam steel INSIDE the beam by cutting down with a special machine ( chain morticer) and bolting the steel to it or put a plate on top with ring connectors or put a steel H beam or the like on top and make it redundant
If the beam is ok (which being oak and big and with mid span support is most probably then the joists are spanning 2.25 m which is OK (just about depending on how strong they are and how much decay there is in the old oak ( I am assuming joists are originial) sapwood etc etc If they need strenthening then that is a bit tricky but can be done but I would not consider it worth it and would insead put on a sheet of ply and make a T beam composite of the lot and then eml and plaster the ply with rough lime plaster (which is what was probably there orignianlly.
It is not likely that it is the joist that are not stiff enough which leaves us with the connections
so... the problem is "extend" the joist so the "new" material (timber) goes into the old bearing in the main girder beam. Suggest this is done with Stainless steel T section from above set within the timbers. I envisage a 80 mm or thereabouts deep steel set 10 mm into the top of the joist bolted to the joist and resting in the old bearing Modus operandi to do this quickly? support joists 2' back from beam lift floorboard 2'either side of beam cut carefully using a specialist tool (hire it) beam morticer 90 mm into the joist from above along the centre of the joist for about 300 mm (or whatever the engineer suggests) cut 10 mm off top of joist to drop in the steel 75 mm from the end drill a hole thru both timber and steel for a bolt recess it for washers and nuts use a plug cutter to cut out plugs to cover nuts with locate Tee section in original bearing on main beam having had a sufficiently size plate put on the bottom to act as bearing or glue a steel plate to bottom of bearing on main beam to take T bar using Thorsman's or similar ss strapping strap one joist to its opposite number relay floorboards
Chris
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