Shell820810 Posted May 27, 2016 Share Posted May 27, 2016 And so the sagas continue. Luckily not our house this time. Sister's house; electricians started on Wednesday after weeks of waiting. The company they went with has contracted the work out to someone else because they are too busy (without any prior agreement or notificiation). They have just went on site this evening to find 4 holes drilled in the joists of the attic trusses, the whole way up the middle of the house. What now?? 1 Link to comment Share on other sites More sharing options...
tonyshouse Posted May 27, 2016 Share Posted May 27, 2016 Not allowed! Trusses are designed on the limit of structural tolerance, electricians and plumbers should learn this at college. rectification work can be expensive, big chunks of timber dog tooth washers bolted all over the hole, designed by an engineer. Best tell the truss company and send photo of damage, they will specify the fix. A plumber once did this on one on my architect supervised jobs, it cost him £400, £100 for engineer and £300 of wood and bolting, he drilled a girder truss two 25mm holes. it ain't good news. Link to comment Share on other sites More sharing options...
ProDave Posted May 27, 2016 Share Posted May 27, 2016 Why are attic trusses any different to any other floor joist? For normal floor joists there are set guidelines where you can drill them and where you can notch them and what size holes or notches. I recall BC inspecting our last house and commenting now neat the notches in the joists were for the run of pipes to the boiler. Link to comment Share on other sites More sharing options...
Shell820810 Posted May 27, 2016 Author Share Posted May 27, 2016 Link to comment Share on other sites More sharing options...
Shell820810 Posted May 27, 2016 Author Share Posted May 27, 2016 30 trusses, easily 200 holes around the house Link to comment Share on other sites More sharing options...
ProDave Posted May 27, 2016 Share Posted May 27, 2016 The NHBC guidelines for drilling joists say a hole shal be on the centreline of the joist, in a zone between 0.25 and 0.4 of it's span, and maximum diameter of each hole 0.25 times the joist depth. I suspect those are too close to then end of the span (i.e les than 0.25 span from the end) but otherwise I would not get worried personally about those small holes. Where else did you expect them to run the cables? You wait until the plumber arrives next. Link to comment Share on other sites More sharing options...
Shell820810 Posted May 27, 2016 Author Share Posted May 27, 2016 From the nhbc calculations these should also be 3" apart, whereas they are 1" apart. I thought they normally run along the joist and up the eaves? The truss manufacturer is being contacted in the morning. Link to comment Share on other sites More sharing options...
Onoff Posted May 27, 2016 Share Posted May 27, 2016 I found this on the subject out of interest: The diagram in my old IEE Guide To The Building Regulations suggests that the holes in the zone between 0.25 & 0.4 can be a CONTINUOUS SLOT without detriment. BUT.....in the new (yellow) OSG it shows separate holes (in the 0.25 - 0.4 zone). Will have to dig out some old OSGs as I seem to recall the same "old" diagram in a previous edition showing a slot ..... 1 Link to comment Share on other sites More sharing options...
Declan52 Posted May 28, 2016 Share Posted May 28, 2016 As Dave says not that much to worry about. As long as they are in the middle and properly spaced that's how it's done. The truss is sitting on wall plate there so I assume it's fixed. A couple of rows of noggins will strengthen the floor up once all the first fix is done. And plumbers are the worst!!! Link to comment Share on other sites More sharing options...
tonyshouse Posted May 28, 2016 Share Posted May 28, 2016 Trusses are different from joists, much more critical it is good that the holes are relatively near a supporting wall plate. good to talk to the truss manufacturer, are there any in the vertical members? Link to comment Share on other sites More sharing options...
Shell820810 Posted May 28, 2016 Author Share Posted May 28, 2016 Their building control officer lets absolutely nothing through, totally by the book. How would you go about rectifying it? The holes are too close together for a start and I don't think they have following the "zoning" rules. Link to comment Share on other sites More sharing options...
ProDave Posted May 28, 2016 Share Posted May 28, 2016 What's missing from that drawing above is that an attic truss will also be in tension to stop the roof spreading apart, perhaps that's why they are more critical? I think the only solution is to get a structural engioneer to either sign it off as acceptable, or if he feels it has compromosed the joists he will recommend remedial action like sistering another joist alongside them. Best also discuss with him what the plumbers can and cannot do befiore they start. They will need bigger holes and more likely notches in the joists rather than holes through them. If they need large holes e.g. for waste pipes they will need a properly engineered solution which may involve a steel plate. It might be advisable to stop the work until you have a definitive answer. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted May 28, 2016 Share Posted May 28, 2016 Tony's right. The holes are WAY TOO CLOSE to the end of the timber and well inside the shear zone. They are also far too close together. My fix would be to pull the cables out and glue and screw some 12mm ply either side of every area like this that has holes far too near the end of a timber. If these are done one side at a time, then drilled, then the other side done and drilled, it shouldn't be a big job. Take the ply back twice the distance of the area with the holes and glue it with a PU adhesive and screw it with relatively short screws, the idea is to replace the lost shear capability in the end. If those holes well away from the end of the timber and spaced further apart them I doubt they'd be a problem. As it is, a significant part of the adjacent nail plate fastenings are really doing much, as they are into a short-grain section. Link to comment Share on other sites More sharing options...
Nickfromwales Posted May 28, 2016 Share Posted May 28, 2016 The pipes will go in the eave spaces. Couldn't be easier. Can't understand why they didn't do this for the wiring tbh. If it wasn't a new build I'd say not to get too panicked about it as I've seen much worse, but as it's a new build then you have warranty and BCO issues so will need to go by the book. Have you / sister paid any money out for the electrical,work yet? 1 Link to comment Share on other sites More sharing options...
Onoff Posted May 28, 2016 Share Posted May 28, 2016 Not saying do it but could you glue tight fitting, wooden plugs in with a high strength adhesive to regain any beam strength lost? Appreciate a hell of a lot of work. Or steel plates with a slot where the holes are? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted May 28, 2016 Share Posted May 28, 2016 Glued plugs wouldn't work, as the glue would be in tension on the short grain section, but plates either side would, but not steel as that would mean drilling more holes for bolts. I think bits of 12mm ply glued and screwed either side would be easier to do. Just cut a stack of bits of ply to size, pull the cables out, and go along gluing, screwing and re-drilling the bit of ply in place then replacing the cables. Get the electrician to pay for it................... Link to comment Share on other sites More sharing options...
Shell820810 Posted May 28, 2016 Author Share Posted May 28, 2016 No money paid yet. Spoke to truss manufacturers and we have to mark the position of all the holes and they will send it to the engineer. There will be a charge for this, which I assume needs to be passed to the electrical contractor. It's a waiting game to see what the engineer says. Link to comment Share on other sites More sharing options...
ProDave Posted May 28, 2016 Share Posted May 28, 2016 While you are in communication with your truss maker, I would also enquire is it okay to drill holes in line with the correct guidance given above or is that a no no. Make sure the electricians and the plumber know the results of their findings. Link to comment Share on other sites More sharing options...
Shell820810 Posted May 28, 2016 Author Share Posted May 28, 2016 The truss manufacturer said they have a diagram marked with the "safe" areas, which I assume will correspond to above. However the holes have just been measured and there is one set 700mm from each end of the joist, and another set in the middle of the joist, as pictured. I don't think any of these fall in the safe area. The span is 9.2m. The manufacturer has seen this before and isn't optimistic, before it has needed new trusses. But they don't know until the calculations have been done. Fixes like Jeremy has suggested might be fine in practice, but building control will be all over this and there will have to be all the documentation for any fixes I assume . Link to comment Share on other sites More sharing options...
Stones Posted May 28, 2016 Share Posted May 28, 2016 4 hours ago, Nickfromwales said: The pipes will go in the eave spaces. Couldn't be easier. Can't understand why they didn't do this for the wiring tbh. If it wasn't a new build I'd say not to get too panicked about it as I've seen much worse, but as it's a new build then you have warranty and BCO issues so will need to go by the book. Have you / sister paid any money out for the electrical,work yet? That's what I can't understand. Surely it would have been easier and quicker for the electrician to fix a timber plank on top of the roof truss onto which he could lay and clip his cables. This is what the electrician and plumber did in our last house. No drilled trusses whatsoever. Also makes putting in insulation a damn sight easier. 1 Link to comment Share on other sites More sharing options...
Shell820810 Posted May 30, 2016 Author Share Posted May 30, 2016 The bank holiday is slowing any progress on this, the engineers are off. They are trying to prepare themselves for worst case scenario. In my opinion worst case scenario is new trusses, that they have to pay for themselves and its game over. They had 40k spend on ground works as they are building on a slope and need to dig very deep and a lot of shuttering needed. It wasn't expected and left the rest of the project very tight financially. Of course hopefully the contractor will willingly rectify the problem, as per structural engineersrequirements, but it could be a court job. Does self build insurance generally cover for this type of problem? Link to comment Share on other sites More sharing options...
ProDave Posted May 30, 2016 Share Posted May 30, 2016 I would really be surprised if the trusses are that tightly designed that these holes have compromosed them too much and they need replacing. Lets hope they either agree it's okay, or agree an insitu repair like a strengthening plate. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted May 30, 2016 Share Posted May 30, 2016 13 hours ago, Shell820810 said: The bank holiday is slowing any progress on this, the engineers are off. They are trying to prepare themselves for worst case scenario. In my opinion worst case scenario is new trusses, that they have to pay for themselves and its game over. They had 40k spend on ground works as they are building on a slope and need to dig very deep and a lot of shuttering needed. It wasn't expected and left the rest of the project very tight financially. Of course hopefully the contractor will willingly rectify the problem, as per structural engineersrequirements, but it could be a court job. Does self build insurance generally cover for this type of problem? The trusses won't need replacing IMO. If they do, I'll be beyond shocked. At the worst they'll need an in-situ repair as suggested above. They'll be over engineered already, so will have a good bit of headroom in them. Please keep this updated though, as it's a good reference for anyone about to get trades in. Oh, and tell your sister not to start removing the sharp objects from the house quite yet Link to comment Share on other sites More sharing options...
Shell820810 Posted May 31, 2016 Author Share Posted May 31, 2016 The engineer came back this morning and confirmed the trusses are OK, and he will write a letter to building control to that effect. So panic over! Luckily. But I don't think the electricians will be back. 1 Link to comment Share on other sites More sharing options...
DeeJunFan Posted May 31, 2016 Share Posted May 31, 2016 Oh I'd say that's a load off! Hopefully no-one else has a go at them! Link to comment Share on other sites More sharing options...
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