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Scottb –
It looks like gluing and screwing is not really an option considering the finished floor above, unless you are going to replace the parquet. You could use the deckmaster hardware but screwing up into 5/8 ply would be iffy – no good grab in plywood. A microlam placed midway, perpendicular to the joists would be much less disturbing to the finished floor and easier, but to preserve your headroom ,(I did this with a flat roof with undersized ceiling joists) support the floor with two sets of temporary shores, cut a short, measured, section out of the center of all the joists with a chain saw perpendicular to the joist run,insert the proper number of microlams of proper depth for the span, support both ends at the walls, insert and nail off joist hangers between the microlam and the cut ends of your joists. Now you have a joist span of 5 + feet and you preserve your headroom and open space. Comments?? Ralph
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We just moved into a 10 yr. old 2 story house. The problem is the main floor living & dining room floors bounce as we walk through the room.
Floor joists are 2x8 @ 16"oc with 2x2 cross bridging. One end bears on 2x4 on concrete foundation wall, other end on steel beam, both ends are end nailed into header joist. Floor is 5/8" t&g plywood with parquet hardwood.
Any suggestions on how to stiffen up the floors??. I was thinking of either doubling up the joists or adding a joist at 8"o.c. with another 2x8 or maybe using a manufactured joist. There is very little in the way of services (wires, plumbing etc.) through these joists so should be fairly easy to add more.
Placing a wall/ support at mid span would not be a good solution as I want to use this area as my workshop.
My theory is that the joists are end nailed over the steel beam on not lapped and side nailed allowing the joists to flex more. Previous house we were in (same builder, same neighbourhood) had the floor joists lapped over the centre steel beam and was not as bouncy as this house.
Scott
*You tell us everything about the joists except the span. Reducing the centers to 8" has the advantage of reducing the plywood span to half. The problem is nailing. Retrofiting joist from underneath at 8" doesn't leave a lot of working room to nail the ends. If you can work that out, I'd go with the 8" centers. If you do this use lots of adhesive on top or you will get squeeks where the plywood is not nailed to the joists.This problem seems to occur much more often over a basement or crawlspace than in second floors. I think builders must be cutting the spans close to the 1/240 deflection limit for unfinished ceilings. I much prefer to size/span using the 1/360 limit and then some more to spare.
*Span is 11 ft.
*11 ft span does not sound like you should have too much bounce. the 5/8 subfloor is a bit thin but i don't know what kind of bounce you're talking about. the kind that shakes the plates in the cabinet? seems like there might be some other reason for the bounce perhaps? join the ends of the joists with some plywood flitch plates.
*Ran into this one time on an apartment complex and found that the decking was stapled to the joists instead of nailed. The spacing of the fasteners was 12" or more also. We added drywall screws on 8" centers and it took the shake out. The architect had specified adding a beam underneath and another layer of plywood (perpendicular) but deleted this after checking the floors once they were screwed. You could consider adding a beam at midspan if it were heavy enough to span across the room below without a center support(possibly a glu-lam). This would give you an open room below.
*Scottb - It looks like gluing and screwing is not really an option considering the finished floor above, unless you are going to replace the parquet. You could use the deckmaster hardware but screwing up into 5/8 ply would be iffy - no good grab in plywood. A microlam placed midway, perpendicular to the joists would be much less disturbing to the finished floor and easier, but to preserve your headroom ,(I did this with a flat roof with undersized ceiling joists) support the floor with two sets of temporary shores, cut a short, measured, section out of the center of all the joists with a chain saw perpendicular to the joist run,insert the proper number of microlams of proper depth for the span, support both ends at the walls, insert and nail off joist hangers between the microlam and the cut ends of your joists. Now you have a joist span of 5 + feet and you preserve your headroom and open space. Comments?? Ralph
*To preserve headroom a steel I beam may be used. Possible as little as 6". Use a larger flang on the bottom than on the top. cut as far into the joists as possible with a skilsaw. Put steel in and cut a piece of wood so the joists rest on the bottom flange. You should only lose a couple inches of headroom and you wont have to worry about cutting all the way to the subfloor.Rick Tuk
*I had this same problem in my brothers house, all we did was installed mid point blocking using 2x8. It took the bounce out of the floor and only cost 30 bucks. I would try this first, if it dont work your only out a couple of bucks
*I have no clear advice.An 11 foot span with a 2x8 is a little thin, but passable. I would have used a 2x10The 5/8 T&G is also a little thin, and I would have used 3/4 T&G.I think the problem is probably deflection on the narrow joists. I would try 90 degree (14 1/2) blocking between them for starters. Quick and cheap. I would also consider doubling up on the joists in the center.Have you had a fat person walk on the floor and actually watch what it does?
*My second floor is 2x8 joists, 16"OC, 12'6" span and then a 2'6" cantilevier, 1/2" ply subfloor and 3/4"HW floor. It's a little bouncy, but it's bedrooms so it's not a big deal. I recently had to double all the joists (sistered) as part af an addition (per engineer). There is no appreciable difference in bounce between before and after. The point is, if you can't increase the depth of the joists, adding more won't help much (unless the deflection is between the joists). The only thing that might help (without increasing depth) is adding wide flange I-joists. Check with a PE or the I-joist Manufacturer.Jerry
*How about sheathing the bottom of the joists with 3/8 cdx? Glued and screwed to make a box beam out of your floor.
*There was an article in JLC about two years ago on this. The basic idea was:jack the floor about 1/4" above level, glue and nail ply to the bottom of the joists making sure there are no joints in the center 1/2 of the span.The nailing schedule given was critial but of course I have know idea what it was now.
*Scott,My wife's Aunt Lucy can make a concrete slab bounce. She made an Adirondack chair I built explode into kindling. Everyone says I overbuild things, but in the back of my mind I think of Aunt Lucy comin' over and going up my stairs or onto my deck. Sometimes I have nightmares about it. you people arent like aunt lucy are you? ;-)
*Thanks so far to everyone for some ideas. No JimL we are not quite like your Aunt Lucy. lolcalvin: yes the bounce I'm talking about is the plates shaking in the cabinet. The bookcase that leans against the wall also rattles against the wall. I'm 200 lbs. and my wife 130 and even she makes everything rattle. But the rattle / bounce seems more excessive than it really should be and what I have experienced in our last house, same size joists same span, but the joists were lapped across the steel beam not end nailed into a header.Ralph Wickland / Rick Tuk: Sounds interesting but the run of the beam would be 25 ft. to omit any centre posts to preserve my workshop space.Jerry: Right now the headroom is 7'-7" I could increase the joists to 2x10 and live with the headroom, but would have to notch the ends of the joist to fit onto the concrete foundation wall and on top of the steel beam. Would this work if I sistered the 2x8 with 2x10?Ron / Ryan: sheathing the bottom might help but would cut off access to the water / electrical in the cavity. (see the other discussion on drywalling basement ceilings.)
*A trick the truss manufacturers use when they goof up around here is to glue and screw 3/4" plywood to each side of the truss to cut out webs, etc. Just wonder if you couldnt rip 3/4" plywood (placing the joints toward the ends of the joists and not the center) in 8'x7 1/4" pieces and glue/screw it to both sides of your floor joists. This is sort of how a box beam is made. Just an idea......
*Scott,Yes, the 2x10's would work even if they were notched. In fact, I don't think they even have to go to the bearing points in order to stiffen the floor.Jerry
*To preserve headroom a steel I beam may be used. Possible as little as 6". Use a larger flang on the bottom than on the top. cut as far into the joists as possible with a skilsaw. Put steel in and cut a piece of wood so the joists rest on the bottom flange. You should only lose a couple inches of headroom and you wont have to worry about cutting all the way to the subfloor.Rick Tuk
*I had this same problem in my brothers house, all we did was installed mid point blocking using 2x8. It took the bounce out of the floor and only cost 30 bucks. I would try this first, if it dont work your only out a couple of bucks
*I have no clear advice.An 11 foot span with a 2x8 is a little thin, but passable. I would have used a 2x10The 5/8 T&G is also a little thin, and I would have used 3/4 T&G.I think the problem is probably deflection on the narrow joists. I would try 90 degree (14 1/2) blocking between them for starters. Quick and cheap. I would also consider doubling up on the joists in the center.Have you had a fat person walk on the floor and actually watch what it does?