Bar Bending Schedule

[Andrew]

Our piling contractor has asked for a bar bending schedule for the reinforcement in our ground beam. The structural engineer, we engaged directly, is saying this isn't in the scope of his works and it's additional cost. Okay, fine, however he says he doesn't have capacity to do it and wants to sub it out. 

 

Seeing as it would be subbed out, has anyone had a BBS produced and is there anyone they could recommend for it. The quote I've had via the SE is a fairly substantial unexpected cost and I'm looking to at least benchmark this.  Thanks. 

[Moonshine]

I had a quote recently from a structural engineer who has the bar bending schedule as a separate unspecified cost, so i am intrigued, to know what one actually is, and what the typical costs are.  

[Ferdinand]

 

i think @Triassic or @Jeremy Harris may have an example. here is a roevious thread.

 

I think it is basically a numbered and keyed list.

 

 

[Jeremy Harris]

Yes, ours was just included with the structural calcs for our retaining wall, last page of this attachment:  20717.pdf

[Moonshine]

46 minutes ago, Jeremy Harris said:

Yes, ours was just included with the structural calcs for our retaining wall, last page of this attachment: 

 

thanks for that as it gives an insight into what a structural engineer calculates, shame i can't read his hand writing.

[Andrew]

The piling contractor has spoken to their engineer who will do it for £250 inc VAT. It's a third of the cost of our structural engineer's subcontractor, so we've asked the piling contractor's engineer to go-ahead. Thanks for the replies. 

[Jeremy Harris]

On 28/11/2019 at 11:44, Moonshine said:

 

thanks for that as it gives an insight into what a structural engineer calculates, shame i can't read his hand writing.

 

 

He's old school, doesn't use a PC for anything, all his work is hand drawn and hand written (these are the drawings: 20130228093748130.pdf ).

 

He gets the lady in the office to scan his hand written stuff and email it out to customers.  Very well known in this area, though, with a good reputation.

[redtop]

yeah ours was included (and simple), looks similar format to Jeremy's

[Red Kite]

And this is part of my bar bending schedule - its totally meaningless to me and just specifies an expensive pile of rusty steel! It was included in our SE's work - and I can't see how an SE can design and warrant a design without specifying the steel he decides is needed - but I am not a Structural Engineer. However being an SE he seems to have built in several layers of 'contingency' - i.e. a huge amount of steel and concrete, where less might have been perfectly adequate. This seems to be the result of our litigious society!

 

 

01 Bar Bending 11.12 Rev B.pdf

[Simplysimon]

2 hours ago, Red Kite said:

However being an SE he seems to have built in several layers of 'contingency'

it was the same with timber, joiner would look at the job and go '6x2', we'll put in a 6x 21/2 to be sure. as you say SE goes waaaay beyond 'a bit more' really covers his arse 'just in case'

[Red Kite]

I think the SE would specify 12 x 4 glulam! (but he might just upsize it to be sure - or hell, costs no issue so lets just go with a monster steel). Given my time again and the huge cost of engineered foundations I would interview several SEs on the basis of 'value engineering' and 'timeliness' . I would pay the best two for a single days work to come up with their draft scheme and cost these up and base my choice of SE on build cost (and timeliness), and not on professional fees. It might be a bit expensive  to run a competition but the scope for savings is huge. I am convinced we are into the 12 x 4 glulam design where the 6 x 2 would have been fine. Once you have an SE on board and he specifies 12 x 4 you are pretty much stuck with it. Though I am also convinced that our basement is 'bomb proof' and I have no worries about its integrity or longevity, which is no bad thing.

 

And humble apologies to any SE's on the board - nothing personal, and our SE is great and very professional; I just feel if it was his own money going into the ground he might have slightly different ideas. And I do know they are constrained by a bunch of legislation and PII issues so its not an easy task.

[MDMbuild]

I found these guys very good

 

They provided a prompt service and even included a 3d rebar model to help to understand the reinforcement detailing relative to the bar bending schedules 

 

[ProDave]

Who in their right mind would use a company like the one recommended above?  Lousy wix.com website and no hint of who they would be submitting an enquiry to, no hint of actual company name, address or how to contact them.  It must be some sort of scam, no real company would advertise like that.

[Gus Potter]

Bar bending and reinforcement quantities! Have written this as I hope it helps all who are doing everything from ICF, piled extensions or just using rebar.

 

I often do these on small domestic projects. I sell this as an extra to the Client by discussing first what type of builder they may want to employ. Take two cases:

 

1/ A house extension.. a few piles with a ring beam. Here your local builder (or you) could maybe get a piling contractor that leaves the pile heads. These are commonly designed at SE stage to be up to 75mm out of alignment and still be code compliant. Next the builder has to figure out how to connect the piles to the ring beam, the shuttering to say get the concrete cover right and all the bars in the right place. Now your local builder may find this a challenge. I say.. hey I'll do the schedule and a shuttering detail. Your builder can then send my schedule to the benders for pricing, make the shuttering and I'll nip by and check it before you pour the concrete.

 

If you want the builder to sort it all out it will probably cost you more than getting me to lay it all information wise out on a plate for the builder. All they need to do is send my schedule out for pricing.. no hassle for them and if no hassle less tends to be added to the price.

 

Or you can get a ground worker that will sub out the piling and do the ring beam.. but someone has to coordinate all this and that is something that comes at a hidden cost.. and you have to take a leap of faith that they are doing it correctly. Better to spend more on good pragmatic design info than have a bad day when it comes to the concrete pour or worse.. once the concrete has been poured and you discover all is not as you expected.

 

Stepping up to say an ICF basement. Here I would push the Client to pay me to do the steel (bar bending) schedule. In fact I would be reluctant to do the job unless I had sufficient design control over it and be able to check on site.

 

What folk don't realise is that when you bend rebar it is not an exact science (bends vary a lot!) and that you need to be very careful to maintain concrete cover, the correct lap length and make sure the concrete can be well compacted at particularly the corners and junctions as that is where you often get leaks. The folk that provide the ICF stuff don't cut you much slack if your bars and in particular the bend radius is a little off. The steel fixer will use what they are provided with and while they will often do their best they can't make a purse out of a pigs ear.

 

Remember that rebar is very heavy and if a rebar cage falls over it could kill someone. I want to make sure that the tying of the bars and temporary stability bracing will be sufficient for it to stand safely during the construction phase.

 

ICF suppliers.. their interests / priorities are not the same as yours when it comes to rebar and so on.

 

Yes some SE's don't do schedules.. years ago it was part of an Engineers training to design a concete beam / slab and produce the bending schedule.. I still remember learning how to do it. The main thing for me is that if I do it say for a basement or say ICF, a retaining wall I have to really look and draw/ model how it is going to fit and if it can be built /poured. It's almost like a last design safety check as when you have to sit down and do the schedule / shuttering you can spot things that you may have missed. It's like another design review/ safety check.

 

If it can't be built as per the design then it's not safe. I could pass design responsibility to say.. well who is going to carry the can.. that is what you need to ask.

 

The sad reality these days is that few designers want to carry the overall design responsibility as modern Clients are often not willing to pay for what they percieve as an extra. Why.. because modern professionals often don't explain (and have often not been taught how to) to a client how they can make savings at the end of the day. I minded to blame the telly.. too much Sarah Beany, Homes under the hammer and Grand designs etc .. well I'm not going to blame myself?

 

If you have the skill to convey to a Client that your way is the most cost effective, efficient and delivers and the Client is not of like mind then you need to walk away from that Client, let them get on with on it. Projects like that often only lead to disappointment on all sides.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[saveasteading]

There is a lot to know in designing the bar bending dimensions. Otherwise they simply don't fit, can be impossible to fix  or can inhibit the concrete pour.

I was taught it but learnt about the real life problems when tasked with coordinating with the steel fixers in a huge hydraulics project. Lots of details had to be altered on site.

In a biggish design office I found that the SEs delegated the Bbs to a highly skilled draughtsman.

It depends how complex your design is, whether the schedule is easy or difficult.

Burning question....who pays if the bars  as delivered, don't fit?

[Gus Potter]

On 09/10/2022 at 10:32, saveasteading said:

There is a lot to know in designing the bar bending dimensions. Otherwise they simply don't fit, can be impossible to fix  or can inhibit the concrete pour.

Hopefully this helps BH folk get a further insight into the ins and outs. Here a few extra of my own thoughts. Take two cases.

 

Case 1..  a simple ground beam spanning over a drain resting on a couple of pads at each end.

Case 2.. say an ICF basement, raft slab with a waterproofing system.

 

In both cases SE say works out the loads and designs the concrete and sizes the rebar. Then often produces a basic reinforcement layout drawing showing bar sizes, concrete cover, durability etc and a few important details; say the lap length, key corners and so on. The SE will usually carry out a review to make sure that what they have designed can be built "somehow?? " (I hear some of you laughing) and markup up the drawings with some CDM notes and so on.

 

This is then passed to the "lucky" Contractor who has to get on with it. The temporary works are delegated to the Contractor as are all the other problems that go with this type of work. The SE may then be engaged to come to site to check the rebar sizes, spacing and so on just before it is all ready to pour. Now that can work ok on large projects where the Contractor maybe has their own in house Engineers who can do all the temporary works design, carefully check the rebar type, spacing, that the bars are all in the right place and has lots of experience.

 

On small domestic projects this often causes problems as smaller contractors / general domestic builders just don't have the breadth and depth of experience or maybe the resources in house. They often need to get someone else in to do the rebar schedule / provide a price so they can tender properly and so on and this comes at a hidden cost, then the need to install all the bars and shuttering and hope for the best.

 

In summary when things don't fit up on site and the concrete is ordered a lot of money can be lost (tempers fray..) usually by the self builder / domestic client.

 

Designing rebar so it fits and the schedule.

 

Once you have done your "SE" bit the next step is look at the bars in detail and start by thinking "what can go wrong here".

 

Extra long bars or bars that are not basically off the shelf at local stockists could come distorted due to bad handling or may be on a longer lead time.. important later if one or two get damaged on site. Cutting and bending rebar is not an exact science, even with modern machinery. All bars have a length cutting tolerance and when you are setting up the bender the first bar may not be quite right, but still in code tolerance. The ones made on a Friday afternoon may not be quite the same as the ones made on a Wednesday at 10.00am. Some can be over bent, some underbent.

 

Also you get what is called spring back, steel is springy so when you put a bend on a bar all bends won't be the same and this can result in quite a difference and this causes problems at corners as for example. You can reduce the concrete cover to the bars. Remember that the bars when they go into the bender may not be perfectly straight to begin with.

 

If that is not bad enough you have to allow for a tolerance on the shuttering. A shutter that is leaning in coupled with a sprung out bar can leave the bar with little of no concrete cover, and as @saveasteading says in cases they just won't fit at all. Bars that lean in can cause bar conjestion and that means that you can have zones where the concrete is not able to be properly compacted.. to be avoided.

 

Often you say to yourself. Hey if I put laps here I can avoid problems with bars fitting over a wide length between two shutter faces. If I'm using cranked bars in say a basement slab with top and bottom bars can I allow the contractor to move the bars a little in case the cranked bars are a little off. If so, how do I convey this "get out of jail free card" to the contractor.

 

Once you have figured this out you go back and check that the SE design has not been compromised. The bar bending schedule is then relatively easy to produce as you have done all the hard work. Then you check it all again!

 

On 09/10/2022 at 10:32, saveasteading said:

Burning question....who pays if the bars  as delivered, don't fit?

It's not just burning it's white hot!

 

Take case 1. A simple beam. I'll do the schedule just working off my 2D cad drawing. Often I'll do this for a nominal sum (fee) especially if it's for a contractor I work with regularly or just "good" for the job. If I make a pigs ear of it then I would expect to foot the bill, but that is a commercial risk I take and is lumped in with the rest of the SE design.

 

Case 2. Ah! Quite happy to do the schedule.. here I say to myself.. 2D is not enough, the risk is greater. What I do is to use say Tekla detailing and model the rebar in 3D and put in the shuttering lines. Now I can really visualise where the problems lie and work your way round the model fixing problems, thinking about buildability, pour sequence and size, the weather / time of year etc.. while all the time asking.. have I compromised the SE design. Another aspect here is to make sure you have all the other information you need to coodinate any service penetrations, water bar details etc. Once all that is done then the schedule is the easy bit especially as the software does a lot of the hard work. But again once you have the output from the software I would spend at least a day checking it, just counting bars and so on and a few other things. Lastly you need to check you rebar spec and so on.

 

Quite happy to do this, put my head above the parapet.. someone has to so why not me? If I get it wrong the bill will land on my door step. However I charge accordingly to carry this risk and am careful about the contract terms. Am I just liable for the bars that don't fit or am I liable for any project delay for example. One claim could be a few hundred, the other many tens of thousands. That is something I discuss with the client about what level of risk they want to take on and how much I will charge for the various risk levels. Usually a sensible agreement can be reached where the risk is shared in an equitable way.

 

The main thing is to have the discussion: Is my fee going to result in an overall saving to the client and deliver what they think they are paying the contractor for in terms of build quality and so on. If yes.. then cart on.

 

Another option is where the Client novates you to the Contractor to do this. Basically the Contractor employs the SE directly and carries the risk. But on self build this is complex contractually especially when you are trying to nail down prices to get say funding for the build.

 

In summary. If you are self building then the above is worth a look at as an approach. It's a balance. The more you spend on the design information the easier (we hope) it is for builders to deliver. Also less risk at tender stage as contractors if they are unsure at tender stage about something will just add on a big number and think to themselves.. if I get the job I can afford to worry later about how I'm going to do it as I have a big profitable lump sum built into my figures.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Canski]

57 minutes ago, Gus Potter said:

Hopefully this helps BH folk get a further insight into the ins and outs. Here a few extra of my own thoughts. Take two cases.

 

Case 1..  a simple ground beam spanning over a drain resting on a couple of pads at each end.

Case 2.. say an ICF basement, raft slab with a waterproofing system.

 

In both cases SE say works out the loads and designs the concrete and sizes the rebar. Then often produces a basic reinforcement layout drawing showing bar sizes, concrete cover, durability etc and a few important details; say the lap length, key corners and so on. The SE will usually carry out a review to make sure that what they have designed can be built "somehow?? " (I hear some of you laughing) and markup up the drawings with some CDM notes and so on.

 

This is then passed to the "lucky" Contractor who has to get on with it. The temporary works are delegated to the Contractor as are all the other problems that go with this type of work. The SE may then be engaged to come to site to check the rebar sizes, spacing and so on just before it is all ready to pour. Now that can work ok on large projects where the Contractor maybe has their own in house Engineers who can do all the temporary works design, carefully check the rebar type, spacing, that the bars are all in the right place and has lots of experience.

 

On small domestic projects this often causes problems as smaller contractors / general domestic builders just don't have the breadth and depth of experience or maybe the resources in house. They often need to get someone else in to do the rebar schedule / provide a price so they can tender properly and so on and this comes at a hidden cost, then the need to install all the bars and shuttering and hope for the best.

 

In summary when things don't fit up on site and the concrete is ordered a lot of money can be lost (tempers fray..) usually by the self builder / domestic client.

 

Designing rebar so it fits and the schedule.

 

Once you have done your "SE" bit the next step is look at the bars in detail and start by thinking "what can go wrong here".

 

Extra long bars or bars that are not basically off the shelf at local stockists could come distorted due to bad handling or may be on a longer lead time.. important later if one or two get damaged on site. Cutting and bending rebar is not an exact science, even with modern machinery. All bars have a length cutting tolerance and when you are setting up the bender the first bar may not be quite right, but still in code tolerance. The ones made on a Friday afternoon may not be quite the same as the ones made on a Wednesday at 10.00am. Some can be over bent, some underbent.

 

Also you get what is called spring back, steel is springy so when you put a bend on a bar all bends won't be the same and this can result in quite a difference and this causes problems at corners as for example. You can reduce the concrete cover to the bars. Remember that the bars when they go into the bender may not be perfectly straight to begin with.

 

If that is not bad enough you have to allow for a tolerance on the shuttering. A shutter that is leaning in coupled with a sprung out bar can leave the bar with little of no concrete cover, and as @saveasteading says in cases they just won't fit at all. Bars that lean in can cause bar conjestion and that means that you can have zones where the concrete is not able to be properly compacted.. to be avoided.

 

Often you say to yourself. Hey if I put laps here I can avoid problems with bars fitting over a wide length between two shutter faces. If I'm using cranked bars in say a basement slab with top and bottom bars can I allow the contractor to move the bars a little in case the cranked bars are a little off. If so, how do I convey this "get out of jail free card" to the contractor.

 

Once you have figured this out you go back and check that the SE design has not been compromised. The bar bending schedule is then relatively easy to produce as you have done all the hard work. Then you check it all again!

 

It's not just burning it's white hot!

 

Take case 1. A simple beam. I'll do the schedule just working off my 2D cad drawing. Often I'll do this for a nominal sum (fee) especially if it's for a contractor I work with regularly or just "good" for the job. If I make a pigs ear of it then I would expect to foot the bill, but that is a commercial risk I take and is lumped in with the rest of the SE design.

 

Case 2. Ah! Quite happy to do the schedule.. here I say to myself.. 2D is not enough, the risk is greater. What I do is to use say Tekla detailing and model the rebar in 3D and put in the shuttering lines. Now I can really visualise where the problems lie and work your way round the model fixing problems, thinking about buildability, pour sequence and size, the weather / time of year etc.. while all the time asking.. have I compromised the SE design. Another aspect here is to make sure you have all the other information you need to coodinate any service penetrations, water bar details etc. Once all that is done then the schedule is the easy bit especially as the software does a lot of the hard work. But again once you have the output from the software I would spend at least a day checking it, just counting bars and so on and a few other things. Lastly you need to check you rebar spec and so on.

 

Quite happy to do this, put my head above the parapet.. someone has to so why not me? If I get it wrong the bill will land on my door step. However I charge accordingly to carry this risk and am careful about the contract terms. Am I just liable for the bars that don't fit or am I liable for any project delay for example. One claim could be a few hundred, the other many tens of thousands. That is something I discuss with the client about what level of risk they want to take on and how much I will charge for the various risk levels. Usually a sensible agreement can be reached where the risk is shared in an equitable way.

 

The main thing is to have the discussion: Is my fee going to result in an overall saving to the client and deliver what they think they are paying the contractor for in terms of build quality and so on. If yes.. then cart on.

 

Another option is where the Client novates you to the Contractor to do this. Basically the Contractor employs the SE directly and carries the risk. But on self build this is complex contractually especially when you are trying to nail down prices to get say funding for the build.

 

In summary. If you are self building then the above is worth a look at as an approach. It's a balance. The more you spend on the design information the easier (we hope) it is for builders to deliver. Also less risk at tender stage as contractors if they are unsure at tender stage about something will just add on a big number and think to themselves.. if I get the job I can afford to worry later about how I'm going to do it as I have a big profitable lump sum built into my figures.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What an amazing, concise and informative reply. After the day I’ve had this has actually refreshed my brain. Thank you. 
 

[Gus Potter]

15 minutes ago, Canski said:

What an amazing, concise and informative reply. After the day I’ve had this has actually refreshed my brain. Thank you. 
 

Thank you for your kind words, much appreciated.

 

It took me a bit of time to craft that. It's not perfect but BH is great and nobody jumps down your throat for a typo etc.

 

That said I learn loads here from other folk so for me it's a two way street. You give what you can and your efforts are returned in kind.

 

Hope tomorrow is better.

 

 

Edited October 11, 2022 by Gus Potter