Monday, October 08, 2012

PEB, PEMB, PMBS Cold-Formed Steel Sheds and Canopies #pt2

Industry must be picking up, projects hanging around from end of last year finally got go ahead, and enquiries from old and new in the shed/canopy industry. Some looking for software, whilst others have issues with size of sections their designs currently use and being unable to compete.

The cannot compete because of size of structural section doesn't make sense to me, and never as and probably never will. I know it is possible to put a product in the market which is some 8 times more expensive than all other products in the market, and for that product to grab the majority of the market displacing all other players. And I know that this is because of a better product design: stronger, more durable, more robust, functionally safer, and better aesthetic.

I also know that the costing methods employed in the building industry are over simplistic and unrealistic, being based on $/metre or $/tonne. These approaches are fine for ball park figures determined by quantity surveyors to determine if project is feasible for the intended buyer. But such costing methods are inappropriate when in a highly competitive market. Highly competitive market does not mean that supplier should keep dropping their costs, rather they should be able to identify cost, quality and value.

I read somewhere that 2/3 of manufacturing costs are tied up in inventory. But do not be confused, this did not relate to funds tied up in raw materials stuck in a warehouse, nor to finished product locked in a warehouse. It related to the costs associated with managing an excessive number of components and excessive variety of products. Benefit comes from the discipline of Design for Assembly (DFA).

For example if have a product which comprises several parts which are bolted together, then that represents a large number of components to be designed, documented, fabricated and handled. If redesign so that can be welded together,then at the minimum eliminated all the bolts, nuts and washers, and replaced with welding wire. Further redesign however can eliminate the welding wire, and simplify to a few die-cast or injection moulded parts which simply clip together. Still further design and can reduce to a single part. There is a lot of cost tied up in having multiple parts.

A few years back the ASI developed a rationalised costing methodology in an attempt to get better pricing of steel structures rather than based simply on $/tonne, it had cost factors for various fabricated parts and assemblies. Unfortunately it is probably seen as too complex and time consuming to be used for one-off-projects. The shed and carport industry however is a different matter: for a single design is used for production of multiple units. Determining cost, waste and lack of quality is important to staying in business.

In rough terms once a structure is engineered, then the quantity of steel in the structure is fixed: however the steel can be redistributed to achieve fewer parts and lower labour costs. Costing a building on the basis of $/tonne therefore doesn't give an accurate cost of the building. Similarly steel erectors basing their fees on plan area of building doesn't give an accurate indicator of cost. Such costing approaches also hinders any improvement and innovation in the industry. Reduce the number of operations, or reduce the time to construct a building, and there is no cost benefit because the tonnage of steel not changed and the floor area not changed.

Now the cold-formed shed or carport industry is seen as an easy entry by builders, since little setup cost. Get a standard design which envelopes most of the buildings in expected market. Then fill in purlin punching sheets and send off to rollformer. Then a pallet of steel: girts, purlins, frame and cladding is then delivered direct to site, another pallet coming from supplier of any fittings required. A workshop may be required, if frame members have to be mitre cut and end plates welded. This requires the rollformer to deliver to the workshop rather than to site, thus involving additional processes, handling and transportation costs. Since the traditional cold-formed shed has welded end plates, the latter approach has been the more common. So straight off there is a cost difference for new players who can use straight cut c-section direct from the rollformers, and who have some standardised connection components. Such cost difference means that one supplier has potential to supply a given shed in larger c-section.

Should also consider the basis of standard calculations. Shed manufacturers want standard calc's on the cheap, so they state the span and size of c-section they want to use and then want calc's for maximum height, they can then use such calc's for any building which falls within the span and height envelope. One manufacturer wants to use C25024, another C20019: depending on wind loading: C25024 can get to height of 6m plus, whilst the C20019 to around 4.8m. But the majority of the market for both suppliers is 2.7m high, for which C15024 would be suitable.

{On notation: C-sections and z-sections are typically described by depth and base metal thickness (BMT), so C15024, refers to c-section 150 deep made from 2.4mm thick steel. On site can only measure the total coated thickness (TCT), which is the BMT plus thickness of galvanised coating. The notation isn't very useful because it ignores the breadth of the flange and dimensions of the lip used to stiffen the flange, such vary between manufacturers, so not altogether interchangeable.}

So its not really a structural issue, its a matter of the economics of getting designs. Most fabricators get designs on an as needs basis. The consequence of which, is that the designs rarely envelope one another in a rational manner. They therefore do not have designs which indicate the limitations of the available c-sections. Further more there is no mandated size for the structural sections, the fundamental requirement is that the structure is suitable for purpose, and that involves more than assessment of stress and strain, or strength and deflection.

We have the pre-engineered timber framing code AS1684, because in the past builders working on the same new development complained about the size of timbers used and argued about not being able to compete. Why can they use 70x35 F7 studs and I have to use 90x45 F7 studs? Well the answer isn't about minimum strength of the structure, but quality and robustness of the structure. For example, I know a builder who wouldn't use anything less than 45mm thick for the wall studs. The reason is that 35mm is too thin when it comes to installing plaster board panels. When 70x35's are used additional studs have to be installed where the plasterboard sheets butt: this may be at every 2nd stud. However it is unlikely that the plasterboard installer will have the extra timbers and install: it is an interruption to their workflow, and extra cost and operation. If the builder puts in the extra stud, chances are the plasterboard will be installed differently and the butt joints won't aligned with the extra studs. The production process is therefore more quality robust if the larger 70x45 studs are installed throughout. By having the pre-engineered solution in the form of AS1684, builders can check the minimum structural requirement and then factor in all the other issues themselves, and thus avoid arguments with the engineer of having oversized the structure. Unfortunately it does contribute to fostering the mentality: that its the law how large a structural section should be. There is no such law.

This mentality leads to industry associations writing silly letters to Standards Australia, complaining about internal pressure coefficients. We cannot compete because others in the industry are using lower internal pressure coefficients: its the law that the internal pressure coefficient should be ??. No it is not, there is no law. The fundamental law is that the structure is fit for function, suitable for purpose as demonstrated by compliance with various performance criteria of the Building Code of Australia (BCA). The BCA is the subjective opinion of a committee or individual people: it is not science. Hence we argue, why do we have to design for this load, where does this load come from. So make a change to probabilistic design, then argue why 1/500 probability of exceedance for wind loading, why not 1/1000.? Simple answer we tried 1/1000 from 1989 to 2002, building industry complained about increase in wind load compared to previous permissible stress design. So as a matter of subjective opinion and judgement the value was changed to 1/500, increasing risk of failure. It is not however necessary to wait till the codes change, it is upto designers to justify their design decisions. For example prior to 2002, I was using the probabilistic models in the appendices to wind loading code (AS1170.2) on a regular basis to assess carports and verandahs which had been constructed without approval. The construction took place many years before, the city councils discovered and imposed a requirement to seek development approval or remove. By making use of the appendices and commentary, need was shown for the methods, that 1/1000 not suitable for all structures. The result being that the methods were shifted to the main body of the code, and expanded.

There is no sense in taking pride in merely complying with the code of practice. Such attitude simply says the supplier would produce rubbish if no code of practice was in place. A quality supplier is one who sets the standard, who designs to their own standards, and their standards exceed those which are mandated. Further more their standards continue to surpass mandated standards even when the mandated are improved.

We appear to have an industry, that wants to say this is the legal size of c-section to use, if supplier using anything else then illegal, shutdown their operations, so that I can have more of the market. Not really business, complaining to parental government, rather than stand on own two feet. The suppliers which loosing business too, follow the same code, they get approval. Designers using the same codes, and working from the same customer brief will design two different buildings. If not either they are both hopeless designers or the codes are too restrictive. Performance based codes are not too restrictive, prescriptive codes are too restrictive.

So one supplier has design based on C25024, not because that is the minimum size which can be demonstrated suitable, but because, that is the size specified in their enveloping design, if they had more designs they could use smaller section. If the industry had software, as it increasingly does, then all would be getting closer to the C15024 of the example. But there are still a multitude of parameters to judge, which have to go into the design, which can result in a still smaller section size, or which may result in a larger section size. Design is subjective, and even science based engineering design does not produce a single result because the inputs are subjective.

Now from the example in the first place, the market place does not have a supplier who is supplying the minimum size section, only a supplier using a smaller section. So straight out minimum size section is not the issue, just lower price than competition. Now if the suppliers all have sheds based on different size sections, then customer is not comparing apples with apples. Now retail sector already introduced unit costing, or was that had imposed on them. The purpose of the unit costing is so that customer can getter a better feel for comparative prices. That is the larger can of food has a lower $/gm than the smaller can, so whilst the smaller can costs less, the buyer is paying more $/g for the contents. However, the smaller cans have added value to some users, and so there is more to consider than $/g. However for the shed customer $/tonne or $/m may be a useful comparison. But not if the manufacturer has costed all buildings on the same $/tonne or $/m rates. The customer needs assisting with value analysis, which is going to be a problem for the industry because they cannot value their own products, so how is the customer going to assess comparative value. Can only really be competing on price alone, when comparing like with like: exactly the same product. Comparing like with like is retail sector, and the primary issues are not the goods bought, but proximity and convenience of access to supplier, and quality of service provided by supplier.

Shed and carport suppliers do not supply the exact same collection of goods and services, they do not have anything which can be compared like for like, they cannot compete on price. If potential customer makes a decision based on cost to them, then the other suppliers have failed in the sale of their goods and services: not in the magnitude of their price. Dropping the price is not the requirement, making the customer aware of the value of the goods and services offered is the requirement. In the main most customers are just plain unaware of how appallingly useless most shed suppliers are at getting development approval.

Which raises another issue. Elsewhere in the world they refer to pre-engineered buildings (PEB), or pre-engineered metal buildings (PEMB), or pre-engineered metal buidling systems (PMBS). For the most part there appears little pre-engineered about the structures and buildings and, high end software is used to achieve rapid custom design. However, whilst the terms PEMB and PMBS are seemingly used interchangeable, I think a distinction should be drawn between buildings and building systems. A pre-engineered building system (PBS) is a collection of pre-engineered components which can be used to design a large variety of buildings. Whilst a pre-engineered building (PB), is an entire building possibly designed from a PBS, there can be no custom variations what so ever to a PB. A kit form garden shed or lawnmower locker is a PB. Light industrial buildings however are more typically PBS, which require custom engineering to transform PBS into a building. The cold-formed shed and carport industry in Australia does not have a PBS, it has standard calculations for portal frames (gable frame). To fit doors larger than the spacing of the frames, they crop the columns, the standard calculations then become invalid, for now have a different rigid frame. To meet customer requirements, salespeople are making unacceptable changes to what is closer to a PB. The result is either delays in getting council approval, or approval being granted by building surveyors who have poor understanding of the structural form and treat in similar manner to timber framed house construction: namely lintel required to support the rafter of the cropped frame. The process would be equal to car salesman agreeing to supply customer with a 3 wheel version of a 4 wheel car, because the customer thinks would be cheaper to maintain. Cheaper to maintain possibly, but not going to get except for major RD&D investment, at significant expense and over at least 5 years.

The building industry can only do things by calculation if there has been research to validate the calculation models. The cold-formed shed businesses are not putting in the RD&D they rely far too much on external consulting engineers. Engineers, who in many cases should stick to concrete, for they have inadequate knowledge of steel design, and don't put effort in to achieve necessary competence. Why would they, if they rarely get asked for such designs, because its mostly for standard calc's or variations to on an as needs basis every few years, if not long periods of 10 years or more: and then back to concrete design. Get the picture as to why the connections are not fully assessed, and thus can be demonstrated inadequate. Full engineering can push the others out off the industry, not necessary to drop price. More necessary to demonstrate have a quality product: both in terms of goods and services.

Back to Design for Assembly (DFA) issues. It would be inappropriate to price c-sections or any structural section soley on the basis of $/tonne of the raw material. The difference in price of a C25024 and a C15024 should not be merely the difference in weight. Australia's shed industry currently built around c-sections, rest of world largely built around tapered sections fabricated by welding plates. With tapered sections, typical structural form is a 3-pinned arch: the heaviest part of the section being at the knee. Alternative to welding up from plate, there is the option of cutting an approriate sized universal beam (UB) diagonally and then welding on additional flange plates to create tapered sections. From this approach, in very rough terms, can see that halving the amount of steel compared to using a constant size section: {eg. get 2 rafters from the one length of UB}. Similarly when using c-sections back to back to form I-sections, it is apparent that end frames have half the load width, and therefore only a single c-section is required for end frames. However, when making frames in UB, making the end frames from parallel flange channels (PFC) is a false economy. It introduces additional components, to be detailed, fabricated, handled and transported, and fitted into the production schedule, all for the sake of 2 frames in the over all structure. Further more at a future date the end frame causes problems with extension of the building: since now require a UB frame as no longer end frame but internal frame.

Now with tapered beams and c-sections, may consider that primary input is steel plate or steel coil strip so cost should be soley derived from a $/tonne rate for raw material. But not so, doing so is not realistic cost of supply. Looking at c-sections, manufacturers have a large variety of depth and thickness combinations. To provide this variety they need steel coils of differing thickness, and differing widths. If the raw steel strip coils, are say 2400mm wide, then the rollformer needs to slit these coils into widths suitable for each size of c-section, which may be based more on current demand than optimum layout for the coil. There will thus be waste narrow width of coil of no use to the rollformer. One way to achieve greater economy, is to buy coil already slit to the width required for the c-sections, the supplier of the coils has a different set of economies and can sell the narrow coil strips to businesses which do sheet metal work involving stamping and blanking.

Since C7510 is commonly used for girts and purlins, or more generically cladding rails, it is to be expected that this would have a relatively low price compared to C30030 which is rarely used. It is also to be noted that many of the rollformers only have a single production line. So to change from C7510 to C30030 requires shutting down the line, resetting the tooling, changing the feedstock, starting the rollforming with a lead strip which becomes waste. Due to the waste strip to get the processed started, it is preferable that once a coil is loaded it is entirely rollformed into section. But since part of the production process involves punching holes into the flat sheet, then rollforming into a section and cutting to required length: it is preferable than rollforming be to meet orders. If not too meet orders then can only rollform to typical production length of 12m, without any holes. Stock lengths of c-section have different economic order quantities (EOQ), than rollformed to order. So for example the thick rollformed Duragal channel (upto 8mm) is typically not economical for builders to use for beams in house renovations  because minimum order length of 6m from some suppliers is too expensive and a waste of material for the typical projects. Builders need suppliers who can supply lengths to order, for such suppliers the offcuts have markets.

A shed manufacturer rolllforming their own materials can achieve benefits by having at least 3 production lines:

1) Cladding Rails
2) Cladding
3) Main frame

Though cladding rails the same size as the main frame can have benefits, and thus reduce the number of production lines. There are benefits also to be had from plain channels which nest, and so can be used as top and bottom plates, studs, as well as splices for other members. Now changing from C25024 to C15024, is less of a burden than changing to C20019. The former only requires change in feedstock strip width, whilst the latter requires change in BMT and feedstock strip width. Additionally with respect to the main frame, changes in section size also require changes in the components required to fasten the frame together. Keep changing the size of section to meet the minimum structural requirement of the frame is not economical, not to mention it causes delays in supply.
One reason for using c-sections over UB's has to do with DFA. If use UB's then typically have cleats welded to the UB's to which the c-section girts and purlins bolted. If use c-sections, then the c-section frame is punched, and the cladding rails are bolted flange to flange with the main frame. The cleats are thus eliminated and the number of bolts reduced from 2 to 1, also bolt changed from being in shear to being in tension. Still further reduction can be achieved by using Tophat's for cladding rails: no pre-punching is required for these, they are fastened in place with self-drilling screws.

The greatest reduction of all is just to have the cladding: no frame, no girts, no purlins. This is the approach taken by USA buildings direct, which has a deep cladding profile, used to build arched buildings. Which appears to be a derivative of the Nissen and Quonset huts of World War II. Not sure how they put light fixtures and such in, without putting holes in the building fabric, but should be ways, not all that different than shell of a car, ship, or aircraft. Anyone, running around finding consulting engineers, to produce standard calc's for lighter shed structures, is not the way to innovate and compete. Engineers need to be on staff, and continuously assessing variations in design, take both end-product and production process into consideration.

Often automation requires heavier sections than manual operations, but the benefit is faster production and more consistent quality of product. Drilling holes manually is slow, and welding is preferable. But manual welding is a high skilled activity, so when the skill not available bolting is preferable. Hotrolled sections typically had to be drilled manually. The drilling was slow, however, cleat plates being small, easy to handle can be punched to form holes. More than that, cleats can be cropped to length and punched with holes in a single operation. So producing cleats and welding to a UB, is faster than drilling holes along the length of the UB for flange to flange bolting. But then rollformed sections came along, these can be punched with holes rapidly, so if suited for frames, can produce a steel framed building more rapidly than with hotrolled steel.  Though it should be noted that prior to hotrolled sections, the traditional way to produce an I-section, was from plate and angles, and lots of rivets: thus lots of rivet holes would have been required. Thus expect that where these riveted beams were being used that technology would develop for rapid production of holes, and so it is that automated beam lines would have taken their initial form. Today there are hi-tech CNC automated beam lines for drilling and welding of hotrolled sections and otherwise fabricating castellated sections and tapered sections. But I hazard that where c-sections are suitable, then c-sections would dominate the market sector. It should also be noted that c-sections typically fabricated from steel with yield strength of 450MPa, whilst hotrolled steel typical strength is 300MPa. Given we don't have mandatory deflection limits, the higher strength steel gives a lower weight structure than the hotrolled steel. If deflections are considered in design, then makes little difference because elastic modulus (E) is the same for both strengths of steel: and a section with appropriate second moment of area needs be found (inertia Ixx, Iyy).

Since deflections are not mandated, once again different designers can make different judgments about appropriate deflection limits and consequently will produce differing designs: one lighter than the other. But does this mean the lighter structure automatically costs less. The simple answer is no. The ligher structure likely to require more fabrication: tapered beams versus UB. If using C-sections, the lighter structure may require more frames placed at closer sections, it may require more flybracing, and it may require connection components not held in stock due to little demand for. Each and every manufacturer has to determine their own production economics, and not compare product to others on assumption of similar production costs.

If a manufacturer or supplier starts off using C150's then they want to get the maximum range of possible buildings from those C150's, so as not to require fabricating additional connection components for say C200's, or should they move into using say C250's? Where does the larger sector of the market lie, would they be better off introducing frames from C250 and having slightly oversized for some buidings, or introduce C200's and loose some projects because cannot accomodate?

We have the simplified wind loading code AS4055, due to economics of manufacturing. It is easier to produce windows and doors suited for wind class N1, than to mess around producing such products for a continuous spectrum of loading conditions. Its better to design for a step class of loading conditions, than a continuous spectrum. Similarly the residential slab and footing code is written around stepped classes, rather than a continuous spectrum. Sure if at the lower end of the class, then custom design may prove more economical on paper, but that doesn't mean that it is viable to get the materials or components. For example the span tables for wind class N1 and N2 are the same: this is largely because something other than wind loading is controlling member size. However, if at the lower end of wind class N2, it may be economical to get tie-down system designed for the AS1170.2 wind load, rather than for the wind class. But if choose to do that, then future attachment of a carport may be problematic, because won't have any reserve in the connections for the extra uplift from the attached carport. Cheaper now, problem in the future. And even if do this for tie-down, the off-the-shelf framing brackets which choose to use, likely to have some surplus capacity, since cannot get the calculated capacity exactly. Further the windows will still have to be N2, if want custom designed then they will be more expensive. Custom designed and custom manufacturerd costs more than stock standard off-the-shelf.

The reason people buy cold-formed sheds is because they want to avoid the delays of design, they want buildings which are already approved for purpose, and so development approval will be a simple matter, and fast. They also want the buildings supplied fast. Delays caused by not getting approval, by not having the right materials in stock, by not having the right designs available, all becomes an irritation to the buyer. The buyer could have gone to an architect and engineer in the first place, then shopped around to find a builder, and got prices on more or less the same thing from each builder. But they didn't because this industry, said it had buildings available, could organise development approval, and custom manufacture. Problem there: is no reference to custom design. Development approval just seen by suppliers as a need to supply a picture of intjention: scribble on an order form. As long as stick within constraints of their standard calc's not a problem, but they are sales people not technical people, they have no idea when they step outside the scope of their standard designs, they rely soley on council to request further information.

Put simply if not buying a shed to put garden lawnmower in, then get drawings produced by an independent party. Take these drawings to the shed producers, and get proper quotes. In first instance drawings don't have to be engineering drawings. The drawings just need detail to obtain planning consent. If planning consent obtained, then can consider requirements for building rules consent. If buying a shed still don't need engineering drawings, but do have to cover all the architectural building issues of the building code. Once got the architectural issues resolved then shop around for service and price. {Don't need building rules consent,just documentation with a high likelyhood of getting the consent without modification.}

If go direct to an engineer, then chances are they will not design anything which is available from any of the shed suppliers. Treat similar to housing. Get plans drawn up, then shop around builders. The builder choses a  timber supplier, and the timber supplier gets a timber estimator to do a materials take-off to the timber framing code (AS1684) or otherwise choose a truss manufacturer and they use software to size the truss members. Once a materials take-off is produced, it is submitted to council to obtain final development approval. All other BCA  issues have however been resolved before the timber framing is sized. Most shed manufacturers and suppliers do not build the shed, nor do they do any of the required siteworks such as carparks, stormwater drainage. So that low cost shed can suddenly become a pallet full of steel dumped on site, waiting for someone to build.

If shed supplier doesn't erect the steel work, they may recommend a builder, if they do so, then they are required to offer at least 3 names of builders. Now some suppliers, have the sheds built, using the services of one or more builders. This can be a cost absorbed in the overall price of the shed, or itemised. These suppliers are typically locked into steel erector fees based on $/sq.m some may base on $/tonne. I will hazard a guess that the original fees were based on $/tonne for hotrolled, but cold-formed steel is lighter construction, so converted original fee into $/sq.m rates. Costs and pricing are complex, at the very core is the need to make enough money for food, clothing and shelter, no matter how much work get. The firefighter has to maintain their skills and make a living whether fighting fires or not. Similarly the welder has to make a living, no matter how much welding work available. Therefore hourly rates are not something which can be fixed or locked in at higher values. Time is money, and selling time is nonsense.

If I modify the design of a shed so that the steel erector can construct more sheds in a year, it doesn't mean that they can win work to build more sheds, or that there are more sheds around to be built. If there is lower demand for sheds, it doesn't mean that the price will drop, the builders have less work to obtain their annual income from, the unit cost per shed will slowly increase, and the number of players in the market reduce. It is a complex juggling and balancing act.

But the building industry in particular seems focused on them over there are breaking the law, their products not up to spec, whilst my product over here twice as good as needs to be. Take them out off the industry. Its really technically inept, and plain nonsense. If product is truly better than the competition, then it will sell at significantly higher price. So if loosing sales to lower priced product, then as a supplier, you have little to no understanding of the real value of your product, nor the real needs of the customer.
Assuming customer is driven by price. {eg. they make $200 /year and after food, have $2 surplus at end of year. So buying a $2000 shed as a home, is a 1000 years of savings} Then the aspect of the price to tackle is not the magnitude, but the payment methods. If have to get a loan, then a higher price, means a larger mortgage and higher interest payments. Builders dealing with large volumes of money daily, therefore should get better deals on loans, and therefore potential to offer lower interest rates. The issue is also the total cost of the project, not just the cost of the building. Therefore need to assist the buyer to understand what the total costs are, so that they can negotiate with suppliers. With one supplier the shed may be a higher price, but the site works at a lower cost than another: yet the total costs for the two are the same. But is what the buyer is getting really the same.

Now if the buyer is driven by price and willing to spend time shopping around, are they also willing to spend time getting to understand the differences between products: to become informed and educated about the product. See the building industry in particular is based mostly on supposedly "secret" knowledge, and a lack of sharing, a lot of bluff. There is a fear of getting caught out, a fear of loosing advantage if others know what you are doing. Yet it is through an educated and informed market place that low quality suppliers are pushed from the market. Informed buyers don't buy based purely on price. However, quality and value are matters of individual perception, so sellers have to develop and build those perceptions.

The cold-formed shed industry basically competes on basis: my rubbish is cheaper than theirs, so buy my rubbish. No why would a surf life saving club, be buy a cheap shed to store thousands of dollars worth or life saving equipment? They would only do that because they didn't give any thought or consideration to their needs, and what would make the most suitable building. If buy a camera, a mobile phone, a car, a computer, then have technical specifications available to assist in making choices. If buy a shed or carport, no technical specifications, just silly brochures with pictures of buildings, not necessarily those built by the supplier. They do not supply technical specifications, because they don't have any. If they did have specifications, they would also consider it telling others what is required to start in the industry. Also there is no accounting for getting approval for one thing, and buying and installing something else.

But once again not always clear cut. There are accusations of selling rural sheds for suburban regions. Such may be so, but what is a rural shed? For the most part, rural sheds are designed to the farm structures code, which permitted a 20% over stress: but not on every rural shed, a shed had to meet specific criteria for that to apply. Buildings with large numbers of workers would not comply. Further just because a code of practice permits lighter structures, does that make economic sense to the individual

For a business, even though not required, it may well be beneficial to have buildings constructed for post-disaster level of importance. Then when a disaster happens, the business is first off the mark, supplying people again. Similarly will that cheap farm building, provide adequate protection to pigs and chickens? That million dollar thoroughbred horse, does it want to be stabled in a cheap shed?

The cost of a structure is not purely dependent on its weight, there is all the associated manufcaturing costs. Even if section size can be reduced, there is no particular reason to do so: as it decreases resistance, decreases durability and robustness, and reduces life expectancy of shed and increases risk of failure. basically it decreases its value.

Now if all supplier has to do is order c-section from rollformer, it may appear that cost of c-section is controlling issue. Still however, the different suppliers have differing over head costs, and the workers different expectations of lifestyle they wish to support. More sales staff, then probably more people sat around doing nothing failing to make sales: but still however needing a basic income to keep going. Further there is still the differing costs of the connection components used by different suppliers.

Even though ordering the c-section, rather than rolling in-house, there is still the economics of excessive variety and availability to consider. Set some standards, eliminate some customer choices, and put a larger volume of larger size c-sections through the rollformers facilities and get trade discount, because reduced the rollformers change over costs and the variety of coil strip they have to have on hand.

The more functions in the supply chain under the control of the one supplier, the more waste which can be removed from the process. So cannot reduce the cost of erection when locked into subcontract at $/sq.m, but bring in-house and the costing can be changed. Move more fabrication off-site and into factory, can implement more automation, faster production and still more unit cost reductions.

See! Personally I don't care that C20019 is adequate for a main frame, because I wouldn't want the frame unless it is 3mm thick or greater, but there is no C20030, so may settle for C20024. Then again walls of brick veneer houses are typically 240mm thick, so therefore a C25024 may be the preferred size to go with. Similarly wouldn't want C7510 girts and purlins, stick with C25024 installed between frames rather than to outer surface. Having chosen a larger section, wouldn't stick with typical 3m spacing, would increase this to limits of the C25024. That is having chosen C25024, design structure to suit.

Those C7510 cladding rails, were originally for fencing. They are relatively dismal sections, and can barely span the 3m spacing of typical frames. The result is that cladding is not installed at its maximum span. Cladding another issue of economics, for manufacturers are always trying to make deeper profiles which span greater distances, problem is they also have less coverage: so whilst have fewer cladding rails to install have more cladding sheets to install. Further greater distances between purlins (roof cladding rails) represents increased hazard working on the roof, either during construction or during future maintenance operations. Whilst for the walls, typicall window sill at 900mm and window head at 2100mm, so for typical small workshop/office need at least 4 girts (wall cladding rails, around the girth). For taller buildings, should girts match spacing of some expected future multiple storeys or mezzanines, or simply relate to maximum cladding spans.

Another issue when considering weight, this is Australia, not the USA, UK or Europe, the weight of snow crushing the building is not an issue. The critical loading condition is wind loading, uplift forces, if make the structure lighter, then have to find some other means of providing the weight to hold it down. The solution is usually a lot of concrete in the footings. Concrete may be cheaper than steel, but drilling the piers could be a problem. Also if floor slab to be installed some time after shed has been built then the weight of concrete in slab not available to assist building hold-down, so larger footing piers required at the beginning.

There are more than the structural mechanics issues to consider, to achieve a building structure which can be supplied at the right price, at the right time, in the right condition.

Clearly some of the larger players have better advertising and promotional campaigns than some of the other players, but they don't necessarily have better products. There is little point in smaller players competing with them across the full range of products. Smaller players need to find the right niche market, and out perform the bigger players in that market sector. For example win the larger buildings on the quality of both goods and service. Sure may still loose some on price, but that just means still haven't got the right product: the appropriate combination of goods and services, and still otherwise failed to educate the public.

Think small local retailer versus supermarket. The supermarket is going to beat the small local retailer on price, the small retailer therefore has to determine the right combination of goods and services that the supermarket cannot supply: specialisation. Rather than looking to compete, look at diversification. Problem with shed industry is everyone jumping on same bandwagon, everyone wanting a piece of the same pie. If seek diversity in the industry, then require innovation, and result is creation of a different pie to offer.

If have exactly the same product, then the cost difference would have to be your profit, wouldn't it? Now if the product varies, then what would the cost difference be? Want the public asking questions about the product, not the price. People can cost the materials retail, and then determine they can get the design done, and build themselves for less money. If that happens, then suppliers have got their product all wrong. Given we have a large DIY and owner-builder population, the building industry really needs to improve its product: goods and services.

Mon 2012-Oct-08  00:11

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