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Who is Responsible for Verifying Design Loads?

Who is Responsible for Verifying Design Loads by Contract?

Disclaimer – this and subsequent articles on this subject are not intended to be legal advice, merely an example for discussions between you and your legal advisor.

Please keep in mind, many of these terms are applicable towards post frame building kits and would require edits for cases where a builder is providing erection services or materials and labor.

DESIGN LOADS/CONDITIONS: Plan, drafting, engineering or calculation changes needed due to Purchaser’s failure to adequately confirm criteria in this section, or Purchaser’s desire to change building dimensions or features, will result in a minimum $xxx charge.

It is solely upon Purchaser to verify with Purchaser’s Planning and/or Building Departments, or any other appropriate government, or non-governmental agencies, the ability to construct purchased building(s) at location anticipated, as well as to apply for and obtain any needed permits. All due diligence to comply with any architectural or aesthetic covenants must be done by Purchaser, and Purchaser agrees to absorb any costs associated with compliance.

Purchaser acknowledges verification/confirmation/acceptance of all Building Code, Plan and Design Criteria included on Instant Invoice. Information Purchaser has verified includes, but is not limited to: Applicable Building Code version, Occupancy Category, Ground (Pg) and Flat Roof (Pf) Snow Loads, Roof Snow Exposure Factor (Ce), Thermal Factor (Ct), Wind Speed (vult or 3 second gust) and Wind Exposure, Allowable Foundation Pressure, Seismic Zone and Maximum Frost Depth, as well as obtaining for Seller any unusual code interpretations or amendments.

Seller’s designs are all per specified Building Code and include the use of NDS Table 2.3.2 Load Duration Factors (Cd) as well as ASCE 7, Eq. 7-2 for slippery surfaces. Seller’s designs rely solely upon occupancy category and structural criteria for and at specified job site address only, which have been provided and/or verified by Purchaser. 

It is Purchaser’s and only Purchaser’s responsibility to ascertain the design loads utilized in this Agreement meet or exceed the actual dead loads imposed on the structure and the live loads imposed by the local building code or historical climactic records. Purchaser understands Seller and/or third party engineer(s) or agents will NOT be contacting anyone to confirm.

Dead loads specified on engineered roof truss drawings include the weight of the roof truss. Roof trusses are NOT designed to support ANY hanging loads or ceiling loads other than those specified as special truss loads in the Agreement. In the case of design roof truss bottom chord loads of less than five (5) psf (pounds per square foot) the bottom chord dead load may be sufficient only to cover the truss weight itself and may not allow for any additional load to be added to the bottom chord.

Roof truss top chord design loads of 5 psf (or less) are not adequate for roofing other than light gauge steel.

Seller recommends use of A1V (aluminum/single air cell/vinyl) radiant reflective barrier, an Integral Condensation Control (I.C.C. – Dripstop, Condenstop or similar), solid sheathing (with appropriate underlayment) or Purchaser applied 2″ or thicker closed cell spray foam insulation to help control roof condensation. 

In no case is Seller liable for any condensation issues. An I.C.C., when ordered, is manufacturer applied to roof steel panels only. Seller makes no representation of any R or U value for any insulation or insulation products supplied. In the event Purchaser opts to utilize snow loads, wind loads, wind exposure factors, seismic loads or ventilation of less than those recommended by Seller, or soil bearing capacities greater than those recommended by Seller, Seller and third party engineer(s) are totally absolved of any and all structural responsibility.

Any windows and/or doors provided by Seller are NOT wind-rated, unless specifically noted as such.

Any possible design responsibility for this building is null and void should any structural materials and/or construction be substituted, replaced, depart, deviate, or are otherwise altered from the Seller’s original building kit they belong to, including structural materials from suppliers not authorized in writing by Seller’s owner, or if building is constructed at an address other than as specified on plans.

Buildings Designed/Built to Code

Designed / Built to Code

Sounds pretty impressive to think you are going to be investing in a new building designed and/or built to “Code”.

Right?

Well – maybe not so much. To begin with “Code” happens to be bare minimum requirements to adequately protect public health, safety and welfare. This does not mean a structure built to “Code” will withstand all possible circumstances. As an example, residential structures (R-3) are designed so as there is a 2% probability of their design loads being exceeded in any given calendar year!

So, how does a consumer best protect their interests?

BE AN INFORMED BUYER

Whether investing in a complete building kit, or having a builder provide materials as well as erection labor – if you receive a proposal stating only “to Code” or not mentioning “Code” at all…..

RUN

All proposals and agreements for buildings should mention what Code and Code version is being used. IRC (International Residential Code) and IBC (International Building Code) do have some differences between them. Every three years there is a new Code version published. Each version has latest updated changes due to testing, research and new products being introduced. Your new building should either match your jurisdiction’s adopted Code version or (if no structural permits are required), most recent version.

ENGINEERING

Unless you are building within prescriptive ‘cook book’ restrictions of a Code, I am a firm believer of buildings being fully engineered. Not just engineered trusses (as an example) but every component and connection being checked and verified by a Registered Professional Engineer specific to your building’s features on your site. This is for everyone’s protection (not just yours, but also your provider and any hired builder).

WHAT TO LOOK FOR ON PROPOSALS AND AGREEMENTS

Beyond applicable Code version, there are other factors you should have included:

Ground Snow Load (Pg) in areas where it snows. Ground snow load is not the same as roof snow load, but is important as it affects drift zones on each side of roof ridges. In these areas, roof purlins often must be closer together, larger dimension or higher graded material to compensate for drifting.

Flat Roof Snow Load (Pf) is usually calculated from Pg and incorporates factors such as Occupancy (low risk buildings get a 20% reduction), wind exposure (an exposed building has snow blow off, a protected site has snow sit) and temperature (heated or unheated and well or poorly insulated). Some jurisdictions mandate a minimum Pf, ignoring applicable laws of physics.

No snow? Then Lr applies, rather than Pf. Lr is a reduced uniformly distributed roof live load ranging from a minimum of 12 to a maximum of 20 psf (pounds per square foot), depending upon the area being carried by a given member.

Design Wind Speed in either V (basic design wind speed, sometimes expressed as Vult) or Vasd, in mph (miles per hour). These values are directly correlated as Vasd equals V multiplied by square root of 0.6.

Wind Exposure – rarely mentioned and extremely important. Most buildings will be on Exposure C sites, meaning they must resist a 20% greater wind force than a fully protected Exposure B site. Become more knowledgeable by reading here: https://www.hansenpolebuildings.com/2012/03/wind-exposure-confusion/

If wind exposure is not delineated on a proposal or agreement, it is not a good sign.

Allowable Foundation Pressure – most people are not interested in having their buildings settle. This value relates to your site’s soil being able to support a given value per square foot of building weight INCLUDING roof and floor live (or snow) and dead (permanent) loads. Keeping it simple, easier to dig equals lower values.  In an ideal world, a geotechnical engineer has tested your site’s soils and can provide an exact measure of soil strength in his or her report. Many providers assume a value of 3000 psf, this would exclude soils including any silts or clays and using this as a value could compromise structural integrity.

Seismic Zone: for single story wood or steel frame structures with low or no snow and more than just bare minimum design wind forces, seismic forces will not dictate structural design. However, they should be checked.

If you are negotiating with a provider or builder who is not clearly stating all of these factors, you are very well paying hard earned money for something you are not getting.

Contact your local jurisdiction so you are aware of what Code minimum requirements are. Ask your provider or builder for any additional investment to upgrade to a greater roof load and/or design wind speed – in most cases it is negligible and it allows you to make informed choices as to risk/reward.