Jawbkk Posted July 27 Share Posted July 27 On the drawing attached, I have last night discovered some horizontal hairline cracks in 3 of the joists. They are approx 500mm to 1000mm long. The joist are continuous and supported on the midde wall so the cracks are on the left side (shorter span) as drawn and what is visible. Is the whole joist condemned and no amount of sistering up is going to make thngs acceptable? For all I know there might be other splits in the right hand side but the floor boards haven't been lifted yet. I wanted to avoid touching the right side as that is where the jost are cast into the party wall. The left side is the gable end of the semi. I didn't want to start the party wall act for putting new joists in on what I think now is hangers as this is the preferred way to connect to a party wall to prevent noise transmission through joists? Much appreciate any help. Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 27 Share Posted July 27 Some photos will help. what age are the joists roughly? Older wood is far stronger and cracking doesn’t necessarily mean they’re bad. notching for plumbing is never great as it weakens them but it’s just how it used to be done, and in some cases still is. Link to comment Share on other sites More sharing options...
joe90 Posted July 27 Share Posted July 27 Frankly a lot of old timber will have cracks in it, just the grains drying out not necessarily “broken”. If the floor feels solid don’t fret about it. 1 Link to comment Share on other sites More sharing options...
Jawbkk Posted July 27 Author Share Posted July 27 (edited) Just taken some photo's of one joist.... The span at this point is 2.05m and the joist depth is 190mm (measured) x 45mm. The notch is 30mm deep and there are no other holes for cables, etc. Although technically the notch is above D/8 it doesn't seem to look so bad. (2 x 22mm copper pipes in there) Joists / house is 1970 build. Edited July 27 by Jawbkk Link to comment Share on other sites More sharing options...
Jawbkk Posted July 27 Author Share Posted July 27 Link to comment Share on other sites More sharing options...
Jawbkk Posted July 27 Author Share Posted July 27 When you say 'notching is how it used to be done' MikeGrahamT21, How should it be done nowadays? I thought notching was permitted within 0.07 and 0.25 x span. Link to comment Share on other sites More sharing options...
joe90 Posted July 27 Share Posted July 27 Drilled holes mid timber is best, away from the compression and tension within the joist, also away from nails/screws, however this is ok for cables but not copper pipes that don’t bend much!!!!. @Jawbkk that “split “ is simply grain shrinkage and as I said above is quite normal with old timber. 1 1 Link to comment Share on other sites More sharing options...
JohnMo Posted July 27 Share Posted July 27 Leave them alone, all wood splits as it dries out. Look at any old oak house. 1 Link to comment Share on other sites More sharing options...
Jawbkk Posted July 27 Author Share Posted July 27 OK thanks for the messages. I will have to repair the joists shown on the drawing for the landing / small bedroom as per the PDF drawing as the notches are too excessive and there is a fine crack in the ceiling which to me indicates the beams are perhaps deflecting more than they should. Link to comment Share on other sites More sharing options...
Jawbkk Posted July 27 Author Share Posted July 27 Just wondering when working out the kN/m load...... All my floorboards are up and I stand in the middle of one joist. Is that almost as good as point loading rather than distributing the 900N load over 1m joist length? If there is any weakness in the beam, then this would be the maximum load? Link to comment Share on other sites More sharing options...
Alan Ambrose Posted July 27 Share Posted July 27 >>> Is that almost as good as point loading Strictly speaking you would have to wear ballet flats, be in an en pointe position with one foot and the other raised from the floor - maybe in an arabesque position. First impression is that you are worrying about nothing (sorry to be blunt). Unless there’s a fairly obvious structural crack along the entire length of a beam or a big notch out, you’ll be fine. By all means examine and test by bouncing, observing, estimating deflection etc. Wood is a natural substance and subject to splits, shakes, cracks, warping, twists, knots etc. That’s expected and allowed for. There will be safety factors of at least 2 or 3 or more - and it will all be designed to standard dead and live loads. From memory, live load allowance is 1.5kN/m^2 i.e. ~150kg/m^2. If you really want to go into it, there will be a spec somewhere (maybe a british standard) for what is an acceptable level of cracks, twisting, notches etc in rafters. But in general - that’s just what wood does. And a good builder will have ensured that no sub-standard materials are used in structural positions. 1 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 27 Share Posted July 27 41 minutes ago, Alan Ambrose said: First impression is that you are worrying about nothing (sorry to be blunt). +1, however if you want to strengthen around the cut outs then knock yourself out . Link to comment Share on other sites More sharing options...
Iceverge Posted July 28 Share Posted July 28 You could resort to caveman engineering and just jump as violently as you could on a joist and then guesstimate if would it break with 3 people doing the same thing. If you think not then it's adequate. Link to comment Share on other sites More sharing options...
Jawbkk Posted July 28 Author Share Posted July 28 4 hours ago, joe90 said: +1, however if you want to strengthen around the cut outs then knock yourself out . Didn't get this one Joe... Are you saying it isn't worth it?? Link to comment Share on other sites More sharing options...
Dave Jones Posted July 28 Share Posted July 28 you could allways sister them up with OSB cuts each side with screws and expanding D4 glue. 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 28 Share Posted July 28 4 hours ago, Jawbkk said: Didn't get this one Joe... Are you saying it isn't worth it?? It depends if you think the joists are not strong enough 6 hours ago, Iceverge said: You could resort to caveman engineering and just jump as violently as you could on a joist Yes, do they bend when you jump,on them? It’s about peace of mind, if you’re going to worry about it then strengthen them by either gluing and screwing timber alongside them (sistering) or using plywood. 1 Link to comment Share on other sites More sharing options...
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