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Strongbacks


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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 

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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.

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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?

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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.

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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....

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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. 

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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 by Ferdinand
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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 by Ferdinand
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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.

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