Steel Detailing Estimating Manhours

[300PLUS]

Gents,

What is the best parameters to use in estimating the manhours of a structural steel detailing particular project ?

I was using my 'per assembly manhours consumption' as my basis in estimating projects, and I'm just curious what the professional estimators are using.

Thanks,

300PLUS

[wai]

Gents,

What is the best parameters to use in estimating the manhours of a structural steel detailing particular project ?

I was using my 'per assembly manhours consumption' as my basis in estimating projects, and I'm just curious what the professional estimators are using.

Based on some 19 years of preparing steel details it works out at approximately 16 to 20 hours per tonne.

This can vary depending on the type of steelwork being detailed. If heavy sections are involved, then the hours can come down, and it can go up a touch if it is all fiddly light gauge stuff.

When you look at a drawing and take the tonneage and try and relate it back to the cost per drawing, you will get a false idea as to the cost per tonne as it does not take into account the cost of preparing the 3D structural model.

[300PLUS]

Thanks Allan

[Garry]

Based on some 19 years of preparing steel details it works out at approximately 16 to 20 hours per tonne.

I'd love to be able to charge out that much! You must be rolling in money??? Only joking Wai , but I do manage to detail a little faster than that and as you say it depends on the weight of the sections used and the complexity of the project. A ROUGH guide for me would be:

0 to 30 kg/m Sections -10 hrs/ton
31 to 50 kg/m Sections - 7 hrs/ton
51 to 60 kg/m Sections - 5 hrs/ton
61 + kg/m Sections - 2 hrs/ton

Most buildings less than 3 stories high work out around 6 hrs/ton. This rate per ton decreases as the number of floors increases. I don't have rates for high rise buildings; you won't see too many of these in Ireland .

[wai]

Based on some 19 years of preparing steel details it works out at approximately 16 to 20 hours per tonne.

I'd love to be able to charge out that much! You must be rolling in money??? Only joking Wai

Don't worry, that is what the fabricators base their charge out rates on.

Locally numbers were crunched on the cost of steelwork per tonne, and when everything was boiled down, the average rate per tonne came out at around $1,100 per tonne.

The fabricators don't like paying anything more than $300 per tonne, however they charge out at more than $1,100 per tonne. Projects are costed based on drawings costing $1,500 per tonne.

Unfortunately drafters are at the end of the line, and we end up accepting really low rates.

Many years ago (around 25) I was the Product Development Engineer for Dexion (Australia). Now here we priced our industrial pallet racking below that of our competition, however when it came to commercial/office shelving, it was always priced above that of our competition. This was because in the industrial area, price was the driver, whereas in the commercial/office area, quality was the driver and price was considered to be an indicator of quality. Well, in Australia, Dexion is just about the only major survivor in this sector today.

Price your work too low, and it can be taken as your work is low quality (even though it is not). It all has to do with perceptions

[contactme]

Hello i just want to share my experienced in Structural Steel Detailing that this is one of the hardest parts of civil engineering. You must need professional if you need Steel Fabrication Drawings. If you are looking professional for it then you can contact Structural Drafting India.

[OMG-det]

I have worked on various projects from Infrastructure, Commercial, Industrial, Domestic, High rise etc, from 20 tons to 6000 tons and in my limited experience pricing per ton is best used as a check (or for mining work). I think there are 3 main variables affecting a tonnage rate 1) Complexity, 2) Steel guage (weight per member) & 3) Repetitiveness. Of course there are many other factors which will affect the pricing but I think these are the main ones. You would need to work out a formula based on these factors and your costs to get an accurate figure.

Sorry to be so unhelpful but it can be complex.

[wai]

I have worked on various projects from Infrastructure, Commercial, Industrial, Domestic, High rise etc, from 20 tons to 6000 tons and in my limited experience pricing per ton is best used as a check (or for mining work). I think there are 3 main variables affecting a tonnage rate 1) Complexity, 2) Steel guage (weight per member) & 3) Repetitiveness. Of course there are many other factors which will affect the pricing but I think these are the main ones. You would need to work out a formula based on these factors and your costs to get an accurate figure.

Sorry to be so unhelpful but it can be complex.

A few developments over the past 12 months

I have been working to refine the quotation basis I use. Essentially, I separate the modelling from the detailing. The reason for this is the pitiful information that passes as "engineers details" these days.

As you say, there can be a variation in the amount of work depending on the type of steelwork. Gathering information from various projects I and colleagues have worked on, I have a "formula" I use for both the modelling and detailing tasks.

First, I get the fabricator to provide an estimated tonneage of steel involved. Since I started this, I have had some reluctant to do this as they then cannot catch me out. It is still near impossible to get anything meaningful from the engineers other than an undimensioned stick diagram (or what passes for one). I go over the drawings (provided as PDF files with Bluebeam PDF Revu where I can use the measurement feature to get the total linear metres of steel involved. I do not try and break it down by sections. Now based on the total tonneage and the total linear metres of steel I arrive at an average kg/m for the job. I then use the formula to work out the $/tonne.

I have attached a couple of PDF files.

Any thoughts?

[crtsd]

G'day... nice thread. Had a read through and you have lots of good answers. It makes me think again about whether I've been doing it right all these years.

Typically I work on cost per connection (end of one member to anything else), I know that if I estimate based on 3/4 hour per connection this works fine. Over the past 10 years I have been averaging the time vs number of connections and have been within +/- 5 minutes on almost every job.

As I use StruCad, I'm only interested in the modelling time as I don't need to do any editing to the member and fitting drawings. So this will be different for other 3d systems where you do have to edit the 2d drawings after producing them.

I hope this helps.

Craig

[wai]

G'day,

My estimating graph has undergone further refinement, so here is it.

Basically, any fabricator or builder worth anything will have a quantity surveyor go over the tender documents, so they will know exactly (or almost exactly) the tonneage of steel involved. They will also know the total linear metres of steel involved. If they don't and you have the drawings to quote off, you can measure and scale off physical drawings, or use a program like Bluebeam PDF Revu (CAD Edition) and actually measure off the stick drawing that are provided. Using the total tonneage and the total linear metres you have been given or provided to you, you come up with an average kg/m for the job.

You then go to the graph and establish which range you fall into and this gives you the hours per tonne to prepare the details (model and details). You then multiply that figure by whatever your hourly rate might be to quote on a $/tonne basis.

If you are not given a tonneage because the builder wants to catch you out, you can guestimate an average kg/m and go from there.

In any case, you should include a clause in your quote that is effectively a "rise and fall" clause to cover increases or decreases in tonneage, and even here specify that the tonneage is based on calculated tonneage using a steel bulk density of 7.85 tonnes/cubic metre.

Summarising the graph, it goes like this:

Avg. kg/m^3 ................. h/t
---------------------------------------
> 80 ........................... 4
70 - 80 ........................ 5
60 - 70 ........................ 6.25
50 - 60 ........................ 7.25
40 - 50 ........................ 8.5
30 - 40 ........................ 9.5
20 - 30 ........................ 10.75
10 - 20 ........................ 11.75
0 - 10 ......................... 13

You can decide what to do if the value falls on a boundary

Anyhow, it is a method of getting consistent costs for detailing.

[davmac452]

Some great insights in the discussion.

A little bit off topic, But I am wondering if anyone here has any formulas for estimating on Precast panel detailing. In the past I have just been pricing on hours, from a client who paid by the hour and then from estimating hours and multplying by a rate.

I could continue to guesstimate on hours, but maybe there is a better way. I am think of maybe a lineal wall rate, divide by 2.5 metres to estimate number of panels, then say 3/4 hr per panel to elevate wall, pick off panel and run Strucplus program wich places lift points, centre of gravity and also computes mass and fills in a data table. Finally multiply panels numbers by 0.75 x hourly rate to get a final price and add a contingency to check and issue drawings.

Does this sound ok?

regards David