Thanks very much Ian, that is very encouraging.
If you do come across the calculations, I would be very interested indeed.
My email address is not valid so try g8izy_ @ _ blueyonder.co.uk, obviously minus the underscores.
Thanks again
Steve
Reading your post again, I wonder did you put the ply on top of the joists to form a T beam or did you sandwich them between joists as I proposed to form a T beam.
Just that I cannot afford the extra floor height.
Steve
The ply was glued and screwed to the top of the joists substituting for, but perhaps a couple of millimetres less deep than the more conventional chipboard. I think a difficulty in sandwiching between joists might be in maintaining the strength at the joints. Presumably glue & screw battens to the joists then glue & screw your inserts to these battens? Now if you could somehow get access to the underside of the joists with sheet plywood and complete the box, you are talking about a MAJOR increase in stiffness ;-)
Kerching !! how about making up a timber box beams? A pair of new joists say 65mm deep by 50mm wide. glue & screw 18mm ply top & bottom & slot into inter joist space screwing through existing joists into new ones, or resting onto existing dwarf walls. then replace your original flooring on top of the lot. Could be quite a soundboard you make though ;-)
Another alternative you may be able to consider is known as A "Flitch Beam" I think, constructed by sandwiching a plate of steel between a pair of timber joists and bolting right through.the lot.
If you have the depth between the support walls, add 6 inch deep joists and notch the ends at he support walls ? (I seem to remember that notching to about one third of a joists depth is considered acceptable ) rgds. Ian
I setup a beam with two loading entries: one "U" (i.e. uniform) specified as 0.8, and one "P" (point) at .7m from distance, and a load of 1.6kN.
Yup, I will second that.
That also assumed the leg directly over one joist - if it were to the side a little the the load would be more spread between two (I did leave the load sharing set to 2 however)
I would be a little wary of bolting a joist that is only 100mm high. Your standard 12mm bolts would hence be taking out over 10% of the joist depth at the point.
You could glue, or use the spiked timber connectors on the bolts if going that route. I would have though that just nailing the joists side by side would be enough in this circumstance.
Doable, but possibly overkill. If you wanted a beam stronger than a pair of timbers side by side, then the next option would usually be a flitch beam[1] (i.e. a pair of beams with a steel plate sandwiched between them, and bolted together). Not sure how realistic that is on only 4" of depth though.
[1] Example 8mm steel plate flitch (with red passivated coating):
I'm sorry but access was not what I meant to type!
Neutral axis
Steve
Bolting through the neutral axis will have negligible effect on the stiffness of the beam A 12 mm hole is about an eighth of your depth, Stiffness proportional to depth cubed, so about 0.2% reduction.. There is no need to glue the beams together (as confirmed by my structural engineer)
No problem, you have confirmed what I thought and unless one is a structural engineer it is better to err on the side of caution.
Yes, I see that but wouldn't the fact that the beam was drilled only in the neutral axis i.e. along the centre where I believe that the beam was neither under compression or expansion make this OK? I would also clamp the edges tightly whilst the glue sets.
You are right. I just have an inherent distrust of nails, even big ones!
I did not know about flitch beams. Maybe my thoughts about deep depths of plywood sandwiched between the joists are my primitive way of re-inventing the wheel :-) However that has got me thinking that this might be the neatest, most elegant and best solution. Presumably a steel stockholder would cut and 'passivate' them for me.
Thanks again John.
Steve
Hi,
You could of course "Test" your floor before engaging in all this work, without any Pianos being involved.
You get 7 adult men, who will weigh about 14 stone (75Kg each, 525Kg total), to stand where the heavier piano is to be placed, and 3 adult men (total
225Kg) to stand where the lighter piano is to stand.If the floor survives this test without any groaning, then you can get them to jump up and down to give the floor a shock load.
If you are worried about the point loading then maybe you need to fit steel plates to the floor to spread the load.
Ian.
I would expect it to be even better if you fix a steel plate to the bottom and ply to the top. Steel is better in tension. Just fixing a 3mm steel plate to either side of the joists will make a huge difference as the wood stops the plate from warping and the 4" depth of steel doesn't bend much. My conservatory roof is supported in a similar way by ally strips inserted in channels in the plastic and I can walk on it and I am not thin.
Boinggg said ZBDI - time for bed...
Geo
Very interesting .. could I have you e-mail addy please?
Mail me at snipped-for-privacy@bancom.co.uk I'd be obliged...
cheers
Indeed:) just be careful of the sonic properties of the floor. I'd just double up a few joists, don't reckon steel beams etc are really called for...
you have to be a little careful where you drill - i.e. not to close to the ends or you risk allowing the beam to split.
Plenty of houses have stood for hundreds of years held together by little else. ;-)
Indeed they will - they will drill them for you as well. Superbeam will model them for you as well.
The one in the photo was I believe "E":
So 0.8kN/m uniform load from the floor, a 5.7kN point load at 0.7m from beam F (stringer that carried the main front floor joists - present because getting at the existing lintle would have been too difficult), and a 11kN point load at 2.8m from beam C (triple joist) that carried two sets of floor joists, and a share of at least three partition walls.... oh and a bit of roof.
So all in all about a nominal 20kN or two tonnes in total. The centre span deflection was calculated at just under 9mm.
In context:
You can stick these on each bolt between the beams:
I think that there is definitely some strengthening to be done.
Our original plan to test the floor was to fill three 200 litre water butts to full in the strategic positions and then us and friends to jump up and down to see if the floor failed! This plan fell through, sorry!, once I started taking the floor up and found that it, most probably, would have failed catastrophically due to the poor state that the floor was in and also a lot of past bodges that needed attention.
The point loading is a worry but with the proper cups under the castors and stiffened joists this does not seem to be so much of a worry as absolute strength.
Steve
Wow! Thanks for that John. I don't know why I have not visited your page before. Absolutely fascinating and clear straightforward information but with your knowledge clearly showing through . Bookmarked and when I have the time, I will be going through it all to get ideas for further projects! Tee Hee - expect further questions!
Steve
Beware that some of the planing and building regs related information is now out of date, and other changes are afoot.
(hence if you are planning a conversion - start now, it will be harder later!)
Dear Steve I suspect I am probably the man to help you here as I have a degree in timber engineering (ICST 1975 Civ Eng Dept) and have spent the last 30 plus years working on such floors in a practical fashion. No one in the group has taken into account a factor in the design of timber floors called "Duration of Load". (in essence were you to load a beam say for a fraction of a second it would take 130% of its (so called) maximum stress (derived from 5 min tests to destruction) of
100% by definition and conversely IF you were to load it to as little as 60% of its "maximum" it may well fail though it may take some years so to do. This is particularly true if the timber is green and goes through the fibre saturation point under load and vast proportional creeps are manifest... So you need to take that into account and the Codes of Practice do so.On a practical basis you need to do the following
carefully identify and lift up the floorboards (marking with pencil so you know where they come from) the board in the areas of the pianos and beyond the next wall plates - staggering the cuts (if needed) to alternate joists and cutting on the joists. Use a right angle square pencil and ~Fien multi master to get neat cuts or lift all the board Once you have access to the sub floor (check ventitlation whilst you are at it) check the structure of the sleeper walls and that they are sound enought and founded well - improve if needed Consider at this point if it is worth it putting in an addtional sleeper wall - the closer to you point loads the better consider putting in INDIVIDUAL supports to the concrete as suggested by others whilst on about the concrete consider a trial pit remote from the load to see how thick it is and if it is ok fine If not spread the load on the point supports with 4" of new concrete with 142 mesh so it is over the old concrete I guess about 1 m square for each corner would be more than ample but if in doubt calculate (engineer)
Next simply run more 4" joists alongside the old ones on the existing and new wall plates such as to cover the 6" of your spreader cicles - that is only likely to be 3 or at most 4 new joists between the two wall plates for each of the legs and with a bit of luck two will coincide!
4 x 2" does not cost much and it is not likely that you will need much more than 8' for each set of 3If you are fussy screw or nail them together so you get a shared effect and avoid individual variations in strenth becoming manifest
lay floor boards back down - I would use brass screws but I am fussy
Any problems come back to me If you can scan and send me a plan locating point loads and existing wps I will work out a rough idea of where to go should you so want on our pro bono terms - ie FOC - you indemnify us! Chris
No need to worry, we did - at least implicitly...
I used a loading duration of 1.0 (long term) on the calculation I did with superbeam. ;-)
Yes, probably about two thousand books.
Robert
Thanks Chris and I apologise for the delay in replying - we had a bit of a break from floors and the computer whilst carol was home!
I had sort of said about the Duration of Load when I mentioned that the piano would not be moved from its place and John has taken that into account but it is something that has worried me as much as the absolute weight.
Yes we have ripped up all of the floor as a lot of floorboards were damaged or left unsupported after plumbing and electrical work in the past. I am adding additional airbricks to improve ventilation. It used to be two rooms, with a central fireplace that was demolished, we think, about twenty years ago. Whoever did it put half of the rubble under the floor and left the joists over where the fireplace was supported on rubble without any dpc. So I am going to have work to do here too!
Thanks again, some very good ideas there. I particularly like the idea of the point support as only one of the legs would be mid-span on a joist - the others are close to a sleeper wall and just the paralleled or tripled joists would seem sufficient. So this is the way I am planning to go.
That is a very kind offer - thanks, hopefully though with an additional support as you suggest and the extra joists I think it will be OK. But if I do run into any problems, I will get back to you!
Cheers
Steve
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