I've just bought a Victorian semi which has suspended floors and luckily a cellar so I can get access below. At some point in its recent history the floor joists have been replaced but its been left with bouncing and creaking in the hall and living room. It has 8 x 2 joists generally at 16 inch centres, with spans of just less than 4m in most places. The new joists were knocked into the outer and central load bearing walls and I don't think I can remove any more brick easily to add extra joists. The hall was constructed differently because it hasn't got a load bearing wall for the end of the 4m span due to the cellar stairs, therefore the hall has 3ft spans across the hallway from wall hangers to the last 4m joist, but this one bows and bends quite a load when people walk above. The 4m span has a second joist which starts the floor of the living room immediately next to it with no gap between. My first question is can I simply sister the 2 joists so that they share the load. I am thinking I would do it with coach bolts (or should I use coach screws, screws or nails)? If so where should I put the bolts (middle or alternating 1/3, 2/3), what size and how often along the length. I can even add a 3rd 8x2 alongside and bolt all together? Next I am wondering if I can add extra 8x2 joists to the other 4m spans by sistering all but around 200m each end with glue, dog washers and coach bolts? Lastly I have a couple of joists where the bricks are slightly worn or just lower and the joists need packing up - is it OK to add a glavanised jointing plate under the joist that will spread the load on the brick to maybe 9 inches? I appreciate any help given.
Yes to everything you asked, with the bolts for sistering top, bottom, top, bottom every 450mm should be ok. Galvanized plate ok.
Thanks very much - what size bolts should I be using - I'm thinking M10 or M12 Coach Bolts? I guess it's a balance between weakening the joist or strengthening the join.
M12 bolts with m12 square plate washers either side and m12 timber connectors in between the timbers.
Can you fit a double joist at right angles to the original. Build piers at both ends with blocks, then wedge in the new supporting joist.
He could but then he will lose 8 inches of headroom in the basement and have to keep ducking under the beam every time he goes past.
Big Dunk is right that I don't have the spare headroom to lose. I've put a couple of acrow props in for now to confirm the issue, and it's pretty conclusive already, so I just need to get some joists now - any recommendations on where to buy from?
Hi Guys, I have a similar problem with a home built in 1860 with floor joists sitting on brick and lime mortar (no so stable). What I would like to do is install under floor heating in between the joists with sand and cement mix but I'm worried about the weight. I cannot support from beneath with a beam so I was thinking of bracing the existing joists with steel strips bolted either side of a few of the existing joists. Any body had and experience with this approach? Any pictures or advise would be very much appreciated. Regards..
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