ashthekid

Reinforced joists for cast iron bath weight?

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Can anyone tell me if it’s advisable to have the new timber frame with timber joists reinforced if you are planning to position a cast iron bath weighing 175kg(without water) on top of it or are standard joists designed to just take that kind of weight anyway?

 

I just want to be sure while it’s still possible to do something about it.

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Mine were all specified as triple joists so I have three sets of triple joists at 400 centres under mine. My bath runs inline to the joists. If it runs across the joists it would be a different matter. Personally I would reinforce under a bath but better to check first with your SE, architect or even local BC for final confirmation about how much.

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So you have 150 litres of water, a 175kg bath and a 75kg person, or 400kg load, at a point on a number of joists. Standard loading is 1.5kN/m2 which is only 150kg so you would need to double up below the bath anyway or reduce the spacing of the joists. The issue usually is that unless edge supported, a bath imposes a point load at 4 or 5 points in a fairly small area with the feet so anything you can do to spread the load is preferable. 

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Ok thank you, that’s good info.
We have some spare steels on site that can be used for this area. 

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12 hours ago, PeterW said:

So you have 150 litres of water, a 175kg bath and a 75kg person, or 400kg load, at a point on a number of joists. Standard loading is 1.5kN/m2 which is only 150kg so you would need to double up below the bath anyway or reduce the spacing of the joists. The issue usually is that unless edge supported, a bath imposes a point load at 4 or 5 points in a fairly small area with the feet so anything you can do to spread the load is preferable. 

 

+1

 

 Worth considering strengthening the whole floor if you are planning to tile it.

 

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I am definitely planning to tile it.

 

Do you think this will work in reinforcing the floor joists?

 

 

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Will what work ..? Not quite sure what the photo is showing ..??

 

Can I check that those floor joists aren’t just bolted to a single 4x2 with one bolt each ..??! What’s below that floor ..?? And what stops the 4x2 buckling ..???

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I’m referring to the extra supports between the joists.

 

The joists are bolted with a single bolt through 50x100mm Grade C16 load bearing stud walls as per Structural Engineer specification. The bath itself is directly above a pantry roughly the same size as the bathroom above. 
In your honest opinion does that sound about right?

 

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Personally I wouldn’t rely on one bolt, single point of failure and would always add 2.

that’s just me, for all the cost of the bolts that’s all

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Single or multiple bolts in timber connections comes down to the loads being imposed. Unlikely the loads will be anywhere close to the shear strength of the bolts so then its down to timber integrity. Large bolted trusses are often single bolt connections allow movement and prevent splitting timbers due to tortional loads.

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Well, I don't think much of your SE - IMHO.

Those joists are pretty meaty, so there's a lot going on out of shot. This is a scenario seen with old school ballon framing, in which studs rose from sole plate to roof plate. For intermediate joists, a bearing support is housed into the studs to take the floor load. No way should those joists be relying on a single bolt into a stud that is not braced.

Whilst not up to speed on bolting schedules -  my inner engineer would use a pair of bolts spaced thirds across the stud & 50mm from top/bottom face.

Those infill pieces look to be lumps of joist toe-nailed into the principal joists. All these will do is brace the joists & not add any dead/live load capability.

To remedy your dilemma, I would rip them out & turn them vertical & attach with joist hangers.

As to better support of the joists, if you are able, look to install a bearer below them & use something like simpson structural screws to attach to the studs. Then reinforce the studs with noggins between screwed to this bearer.

As a young engineer, I was counselled by our structual tutor "If it looks right, it probably is right". In your case, you need to see that those joists are well supported; the studs braced & this extra load supported.

I know, "much better informed - still none the wiser!"

Hope this helps.

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On 07/04/2021 at 23:51, ashthekid said:

I’m referring to the extra supports between the joists.

 

The joists are bolted with a single bolt through 50x100mm Grade C16 load bearing stud walls as per Structural Engineer specification. The bath itself is directly above a pantry roughly the same size as the bathroom above. 
In your honest opinion does that sound about right?

 


So nortmally there would be a top plate on that studwork and the build off it. You’ve got lots in sheer, and nothing stopping twisting or spreading the loads. Fairly crap design IMHO and not one I would be using. 

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@ashthekid can you show us what is below here. I assumed the joists were supported from below and we are looking at Cantilevered ends (continuing over a small corridor or similar)  Reading other replies they are thinking the joists are supported by the 4x2`s Studs.

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On 07/04/2021 at 21:31, PeterW said:

Can I check that those floor joists aren’t just bolted to a single 4x2 with one bolt each ..??!

How do you zoom into photos to see the bolt or how do you see the full resolution photo? I can't make out what's a bolt and what's a knot in the wood.

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8 minutes ago, Dudda said:

How do you zoom into photos to see the bolt or how do you see the full resolution photo? I can't make out what's a bolt and what's a knot in the wood.


28” monitor ..! But you can see the bolt head in one of the photos plus it was confirmed. 

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If this is a cantileverd structure then the bolts would be redundant surely - nails would be sufficient. The OP needs to better describe the stucture.

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Here are some photos from today, hopefully it’ll answer any questions. It’s over a pantry room with another load bearing stud wall approx 1.5-2m over from the exterior stud wall so yes a kind of corridor if you like. I’m told the single bolt will have additional nails/screws going in once all carpentry is installed. 
the extra support between the joists is nailed in multiple times and then supported again underneath again as you can see in the photo. 
There will also be additional stud wall uprights where the bath is going in.

 

 

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Right so it is cantilevered over the wall ..!! Less concerned now !

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10 hours ago, ashthekid said:

@markc @PeterW @PeterTweeter

Any thoughts on my latest photos showing what’s underneath and where the next load bearing stud wall is located for the joists in question?

All good - as i suspected. Single bolt is an odd detail but ive seen it loads of times in heavy Glulam structures to prevent tortional loads in the walls/ends of joists/beams. - By design the bolts should be only just nipped up and not tight but that doesnt really matter

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11 minutes ago, ashthekid said:

The bolts do that the teeth plates for extra grip.

What teeth plates? 

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At least these strengthen the single bolt. From the underside, I can see the 2x's are forming a support platform - not very elegant but ok.
BTW are you paying your chippies/SE by the cube of timber used?

FTW I would still look to further reinforcing the O/B ends of the joists.

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