No matter what kind of building is being considered, some basic requirements are always the same.
Snow and roof loads, energy conservation requirements, frost protection, wind loads, floor loads… all these things do not change.
At least they do not change in the same area. The more south you go from the Town of Webb (or more north you go) the design criteria may change.
The Building Code of New York shows zone maps which indicate what zone, or area, the project will be in.
These maps tell the architect or engineer the basic design criteria needed for a project.
Everything in the structure is then reliant on these basic requirements from the ground up.
Soil conditions may also impact how wide a footing needs to be.
Window and door headers, overhead door headers, special point loads inside the structure, horizontal beams and floor joists are all dependent on the design criteria.
For this area, specifically the Town of Webb here are some of the fundamental criteria;
• Roof systems, 94 – 104 lbs per square foot. This is based on 80 lb per foot baseline, and then add 2 lbs per square foot for every 100 feet of elevation above 1,000 ft.
• Most areas will have a wind zone of 90 mph – category C. This can increase to 120 mph in a few rare cases, usually with long distances of water pointing at the house.
This impacts wall bracing, window impact resistance and roof system tie down requirements.
• 7244 HDD (heating degree day) climate zone 6 for compliance to the New York State Energy Code. Compliance can be shown by two different methods, prescriptive or calculated.
Prescriptive allows a house to be built with up to 10% wall area having doors or windows and with minimum “R” values in walls, roof/ceilings, basement walls, floors or any part of the building exposed to unheated areas.
A calculated method is done by using the ResCheck formula.
By entering in all components of the structure, including doors and windows, entering the “R” values in the different areas you will determine compliance or not.
Either one must be shown as part of the plans.
• Frost depth is 48 inches here. Depending on where the building is, how it is situated, what kind of wind exposure it may have, deeper may be recommended.
• Floor systems depend on their use, living space, bedroom space or storage. 40, 30 and 20 lbs per square foot respectively. Is the attic truss for storage or for a playroom?
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All this stuff should be shown of page one of the plans. It makes it so much easier for the code official if a design criteria chart is shown right on the front page of a set of plans.
At least the code official knows the basics seem to be covered.
All too often that information is not obviously shown.
The energy code calculated method must be a separate document prepared and submitted with the plans.
Occasionally plans are submitted with the warm and fuzzy statement “all local code must be complied with.” That’s a great ‘cover-your-butt’ statement usually found on mail order plans.
If mail order plans are used, they must be reviewed by a licensed architect or engineer, stamped and signed.
They will make appropriate adjustments and note them on the drawings accordingly.
None of this stuff is new; it has been around for a long time, well before the NYS Uniform Fire Prevention and Building Code was adopted in 1984.
Although the actual criteria may be more or less in different parts the state, the concept is the same.
So when we get a set of plans from North Carolina, and the roof system is designed for a 25 lb. snow load, and the applicant says “we will just order the trusses for 100 lb” and the code official still says, “what about all the headers over the doors and windows, or that carrying beam in the basement, or that little support post in the wall” you will realize that it’s whole house that works as a system, all the parts impacting the each other.
A chain is only as strong as the weakest link.