ToughButterCup Posted December 13, 2018 Share Posted December 13, 2018 I don't need them in my floor because the span is less than 4 meters. But should I put one in anyway? Link to comment Share on other sites More sharing options...
joe90 Posted December 13, 2018 Share Posted December 13, 2018 Didn’t have any in mine (4 mtr span). But supported plasterboard edges on all joins and edges with 4x2. Link to comment Share on other sites More sharing options...
Big Neil Posted December 13, 2018 Share Posted December 13, 2018 belt and braces??? Link to comment Share on other sites More sharing options...
nod Posted December 13, 2018 Share Posted December 13, 2018 43 minutes ago, recoveringacademic said: I don't need them in my floor because the span is less than 4 meters. But should I put one in anyway? Hi Ian You don’t need strongbacks in a 4 mtr run If you use 15 boards on the cielings you need any nogs to support the edges on 400 or even 600 centres Link to comment Share on other sites More sharing options...
ToughButterCup Posted December 13, 2018 Author Share Posted December 13, 2018 Yeah folks, I know I don't need them. But I think I'll put some in just for the experience...... (Loads of old 4 by 4 dumped on the site from when we needed to shutter..... ?) Link to comment Share on other sites More sharing options...
epsilonGreedy Posted December 13, 2018 Share Posted December 13, 2018 The industry definition of a nice firm floor is different to the expectation of demanding selfbuilders. Another poster here has previously advised specifying a more challenging max deflection limit when ordering floor joists. Link to comment Share on other sites More sharing options...
ProDave Posted December 13, 2018 Share Posted December 13, 2018 Strongbacks are normally about an inch thick, typically in the order of 6 by 1. At that thickness you can drill or notch them is something large needs to pass through e.g an mvhr duct. If you use 4 by 4, it will certainly be solid, but be absolutely sure you won't want to be getting a soil pipe through there later. Link to comment Share on other sites More sharing options...
Gone West Posted December 13, 2018 Share Posted December 13, 2018 @recoveringacademic The strongbacks used on my joists were 4" x 2". You could just rip down some of your 4" x 4". Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted December 13, 2018 Share Posted December 13, 2018 What is a strongback? Link to comment Share on other sites More sharing options...
Big Neil Posted December 13, 2018 Share Posted December 13, 2018 6 minutes ago, Moira Niedzwiecka said: What is a strongback? Link to comment Share on other sites More sharing options...
ToughButterCup Posted December 13, 2018 Author Share Posted December 13, 2018 @Big Neil, that's a Meat Head. Here's a strongback, @Moira Niedzwiecka Its a bit like a spine.... Ian Link to comment Share on other sites More sharing options...
jamiehamy Posted December 13, 2018 Share Posted December 13, 2018 I nailed mine first as per diagram. Then coach bolted. Difference was noticeable. No reason why not other than services as mentioned. Belt N braces. Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted December 13, 2018 Share Posted December 13, 2018 Thanks. I have been a bit worried about my heavy freestanding bath & wondering if I ought to strengthen the floor under it. Span of metal web joists supported on structural lam wall plate on one side & steel girder on the other with caberdeck floor.TF04 First floor joist layout 220817.pdf I would be limited with how much I could strengthen it because of MVHR ducts & pipes. The wall adjacent to Nos 5 & 6 on joist plan has OSB racking and the bath is about 1 mtr to the right of that. Bath weighs 82kg. Of course, once you half fill with water & get me in it, considerably more. Any thoughts? Link to comment Share on other sites More sharing options...
ProDave Posted December 13, 2018 Share Posted December 13, 2018 Re spreading a heavy load. I did this where my HW tanks sits. It was positioned right central to one joist (near it's end) I wanted to spread the load more evenly to more than 1 joist. So I inserted an extra spare bit of strong back. As well as fixing it in the conventional way. I had it so it's bottom sat (with a small packer) on the bottom chords of the outside joists. Then on the central joist (where the tank sat) I inserted parallel wedges to pack between the top chord of that joist and the strong back. The idea being if the central joist tried to flex when the tank was filled, the extra strong back would directly transfer some of that weight to the adjacent 2 joists. Link to comment Share on other sites More sharing options...
Alexphd1 Posted December 13, 2018 Share Posted December 13, 2018 1 hour ago, Moira Niedzwiecka said: Thanks. I have been a bit worried about my heavy freestanding bath & wondering if I ought to strengthen the floor under it. Span of metal web joists supported on structural lam wall plate on one side & steel girder on the other with caberdeck floor.TF04 First floor joist layout 220817.pdf I would be limited with how much I could strengthen it because of MVHR ducts & pipes. The wall adjacent to Nos 5 & 6 on joist plan has OSB racking and the bath is about 1 mtr to the right of that. Bath weighs 82kg. Of course, once you half fill with water & get me in it, considerably more. Any thoughts? Bit of topic from your question, I would change your centres of joists to 400mm, one of four things I am seriously kicking myself over.... Link to comment Share on other sites More sharing options...
ProDave Posted December 13, 2018 Share Posted December 13, 2018 Also check joist sizing. Most of our joists span end to end of the building, so are sized for the longest span. That means for some spans they are over sized. Above our snug living room some of the joists are smaller, having been cut in 2 by the stairwell, so the joists on one half are the over sized ones, and on the other half of the room are the "correct" sized ones. The result is noticeably more floor bounce one side of the bedroom than the other. I wish I had noticed this on the plans and got the same size joists everywhere. 1 Link to comment Share on other sites More sharing options...
ToughButterCup Posted December 13, 2018 Author Share Posted December 13, 2018 2 hours ago, Moira Niedzwiecka said: [...] Any thoughts? The guidance I have read about strongbacks (in the context of both Easy Joists and POSIs) is that a strongback can only be installed during the construction of the floor - while the joists are exposed. Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted December 13, 2018 Share Posted December 13, 2018 The joists are all in place but are still exposed underneath. I think I will just strengthen as much as possible. I am told that 82kg is not that heavy for a bath & a cast iron one would be about 130kg. Link to comment Share on other sites More sharing options...
ProDave Posted December 13, 2018 Share Posted December 13, 2018 It's the water that makes a bath heavy, not the bath itself. Link to comment Share on other sites More sharing options...
Ferdinand Posted December 13, 2018 Share Posted December 13, 2018 (edited) 1 hour ago, Moira Niedzwiecka said: The joists are all in place but are still exposed underneath. 3 hours ago, Moira Niedzwiecka said: Any thoughts? I think I will just strengthen as much as possible. I am told that 82kg is not that heavy for a bath & a cast iron one would be about 130kg. + up to 80kg for the water. + up to perhaps another 80kg (x2?) for the occupant. = potentially a 400-500 lb gorilla standing in your bathroom. Quote Any thoughts? Swing it from the roof like a hammock? If you are concerned you could bridge the floor area where the bath is going with a more rigid floor to engage more joists (eg one or two thickness of ply, as you would to lay tiles over a suspended floor). Or you could just put a BFO steel plate under the bath as far out as necessary. Or if you intend to cover them up a plate below may do the same job .. effectively giving you a monocoque. You would need to consider finishes, though. Could that be done with several steel rods inserted through a series of joists and attached to each, or something similar, or steel braces done like noggins? F Edited December 13, 2018 by Ferdinand Link to comment Share on other sites More sharing options...
Russdl Posted December 13, 2018 Share Posted December 13, 2018 2 hours ago, Alexphd1 said: one of four things I am seriously kicking myself over.... Further off topic, what were the other three? Link to comment Share on other sites More sharing options...
Ferdinand Posted December 13, 2018 Share Posted December 13, 2018 (edited) 1 hour ago, Moira Niedzwiecka said: The joists are all in place but are still exposed underneath. I think I will just strengthen as much as possible. I am told that 82kg is not that heavy for a bath & a cast iron one would be about 130kg. BUt I think that if I needed to do that, I think I would create a pedestal for the bath of say 1.8m by 1.8m and make that a strong monocoque spanning 4 joists, or alternatively as a raised end of the room. Then treat it decoratively as drawing attention within the room decor. I am sure I recall Sean Connery and a Bond Girl in such a bath, where the bath was a fish tank. Edited December 13, 2018 by Ferdinand Link to comment Share on other sites More sharing options...
Alexphd1 Posted December 13, 2018 Share Posted December 13, 2018 23 minutes ago, Russdl said: Further off topic, what were the other three? More design window location etc. Link to comment Share on other sites More sharing options...
CC45 Posted December 13, 2018 Share Posted December 13, 2018 7 hours ago, jamiehamy said: I nailed mine first as per diagram. Then coach bolted. Difference was noticeable In addition to the nails, I used two substantial screws as well. They noticeably pulled the timbers together more than just the nails & certainly did reduce flex. I'd prob put then in - why now. Link to comment Share on other sites More sharing options...
Ferdinand Posted December 14, 2018 Share Posted December 14, 2018 16 hours ago, recoveringacademic said: @Big Neil, that's a Meat Head. Here's a strongback, @Moira Niedzwiecka Its a bit like a spine.... Ian Looking at that diagram, I'd say that Strongbacks are as much about dampening vibration, as they are about reducing deflection. F Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now