While steel is one of the most durable building materials available, the sturdiness and strength of your steel structure is only as solid as the foundation it rests upon. Many builders will promote different, complex techniques and methods for setting your foundation; and it is important you do not get caught spending unnecessary time and money on foundation adjustments that provide no added benefit to your structure. As long as you follow steel construction foundation best practices, and ensure your foundation meets all Occupational Safety and Health Administration (OSHA) standards and local building codes you will be off to a great start.
In order to obtain a permit for your building, many governing organizations will ask for an 'Engineered Foundation Plan'. This plan is drawn up and approved by a certified buildings manufacturer and contains a detailed layout of all foundation measurements, anchor bolts, reinforcements and footings. Be sure to discuss this plan upfront when deciding between potential manufacturers, as in recent years it has become less common for manufacturers to include this plan in their standard building packages. This became common practice several years ago when the Metal Building Manufacturer's Association (MBMA) released a revised version of its Standard's of Practice, which stated that moving forward it was the responsibility of the building owner to acquire the foundation plan for themselves. Many companies will still offer this plan for an additional fee, so be sure you know exactly what you are getting with the cost of your building up front.
Elements of a Strong Foundation
There are a variety of different foundation options out there and choosing the most suitable one for your needs depends on a few different variables:
- The stability and layout of the terrain foundation will rest on
- Horizontal forces on your structure, such as wind and rain
- Vertical forces on your structure, such as gravity and building load
To determine the type of foundation needed first survey the land where you are going to place your steel structure. Remember to first check all local and state building and safety codes before deciding upon the placement of your structure. Most counties have regulations concerning the proximity between two buildings, or a building and nearby property lines to help enforce fire regulations and other safety rules.
Once you have finalized where your new steel structure will be placed on the property have the land professionally surveyed. The surveyor will be able to determine the grade, or evenness, of the land to make sure it will be able to fully support your structure and it is compact enough to prevent to cave-in's or shifting over time. If the land you're placing your structure on is not flat you may be required to level, or even out, the terrain before continuing with your project.
The type of foundation your building requires depends upon its use and size. Many building customers opt to pour a full slab of concrete upon which to place the building. This concrete slab will provide a smooth floor for your structure, ideal for storage buildings, garages and residential structures and is also the best option for large, heavy buildings or buildings that have to withstand heavy horizontal and vertical loads. If you would rather retain the gravel, or dirt foundation on which your building is placed, or if your structure is light and less complex then it is not necessary to build a full slab, instead several concrete piers will provide enough support and anchor your building.
Anchoring your Foundation
An anchor rod, or anchor bolt, is a steel rod that is either cast, set in concrete or grouted into concrete and masonry for the purpose of attaching a steel structure to its foundation, providing both stability and preventing movement of the building. Anchor bolts are normally provided by the company hired to lay your concrete and put in place when the foundation is being laid. However, anchor bolts can also be placed once the concrete has been laid. There are two types of anchor bolts on the market, wedge anchors and bent anchor bolts, and the use of these bolts depends upon the necessities of the building. Wedge anchor bolts consist of a straight pin with a bolt at the top and used when the concrete foundation is already in place. These anchor bolts are placed in drilled holes and expand once in place. These bolts rely upon the friction of the surrounding concrete to remain in place. Bent bolts are similar to wedge bolts, but have a bent, 'L' shaped piece at the end. These bolts are placed in the foundation as the concrete is being poured and for this reason are extremely resistant to upheaval and ideal for large, heavy structures.
Adhering to Regulations for Anchoring your Steel Structure
Since the effectiveness of your building's anchor system directly affects the stability and durability of your steel structure there are many local, federal and county-based regulations and safety codes that govern the placement and installation of a building's anchoring. Studies have found that errors made in the placement and quality of aching accessories are the most common causes for building structural deficiencies and collapses. These rules vary from county to county and the first step should always be to consult all local building codes, however there are several rules in place that apply to all steel construction projects, including:
- All structural columns on a building must be anchored by at least four anchor bolts
- The placement of all actor bolts on the structure must adhere to the approved Engineered Foundation Plan and all anchor bolts must be placed within 1/16 of an inch of the pre-approved specifications
- Grits and purlins must never be used as an anchoring structure for any building unless written approval is obtained from a licensed building safety specialist
- All adjacent anchor bolts shall have a difference in dimension no more than 1/4 inch
- The height of all anchor bolts within a foundation, measured by the height of top-most part of each anchor rod shall be within 1/2 inch or one another
- All anchor rods shall be placed with their longitudinal axis at a 90-degree angle to the surface of the foundation
Author: Conrad Mackie