Once you have developed a viable design for your container home you will need to analyze your plans them to gain a perspective on the materials you will need since the drawings themselves do not incorporate information on the quality or quantity of the materials.
The materials needed for the project should be grouped together with similar items into a set of schedules, such as doors, windows, etc. The schedules in effect become the specifications of you project and are then used to do what are known as takeoffs, or materials estimates. The schedules are vital, especially if you plan on hiring a contractor to build your home, since it is the only way for the builder to get a handle on the materials and processes required to do the job.
Some materials like doors and windows will be specified on the schedule as a unit, while other materials like concrete will be specified as a cubic amount, or linear feet in the case of lumber. Other materials are estimated in sq foot, or in the case of flooring in sq. yd. quantities. The Resources Section has a number of construction calculators available to help you with these calculations.
Because each project is different the actual details for each schedule will vary according to the requirements of the project but the basics will remain unchanged. A general list of the schedules needed will consist of;
General requirements
Site work
Concrete
Masonry
Metals
Wood and plastics
Thermal and moisture protection
Doors and windows
Finishes
Mechanical systems
Electrical systems
The General requirements are mainly concerned with how the project is to be administered. An overhead summary will help you get a realistic idea of the costs of items and tasks that may not be directly related to the production of the structure but have a cost associated with them non the less.
The main areas of concern would be Testing and Inspection of soils and concrete. Permits and Fees will incorporate the cost of building and occupancy permits, assessments for the connection of utilities, and plumbing and electrical permits. Each locality will have it’s own rules for calculating these fees. Clean up, during and after completion may include costs for dumpster's, and permits for them as well as a cleaning service to provide the final clean up before occupancy.
These general requirements will not be included in the plans but they are definitely an inherent part of the construction process
Site work schedules often involve a high number of unknowns, which can make them difficult to complete since it’s often impossible to know what lies beneath the surface. For example, perhaps there are hundreds of used tires disposed of under the surface that will need to be removed.
Most of the site work will be shown on the civil drawing. If you are going to require grading of the site, the amount of cut and fill required to bring the site to grade must be calculated.
The utility drawings for your site will be used to takeoff the trenching and backfill estimates. Also check the mechanical and electrical drawings for any conduits that are necessary but not shown on the civil drawings.
Some projects may require clearing of trees or grubbing (the removal of stumps). This work may require equipment, or it could be handwork.
Excavation, or digging holes will require the calculation of the volume of soil to be removed, and in the case of drainage and utilities, backfilling. Drainage plans will provide the info needed to takeoff the drainage estimate. Estimating the pipe needed for utilities and drainage must also be calculated. The pipe is taken off as linear feet while the cost of cutting and fitting the pipe must also be included. Some pipe fitting such as PVC pipe can be fitted by hand but large diameter pipe such as ductile iron or corrugated drainpipe may need specialized saws to cut. Special bedding materials such as sand or gravel may be required and must be taken off and added to the schedule.
Other site improvements that need to be included on the site work schedule can include a wide array of miscellaneous items and tasks such as fencing, irrigation or sprinklers, fountains and planters.
The takeoff of concrete work can be organized into several categories. Concrete in taken off the plans as cubic feet and then converted to cubic yards, which are the accepted units for both estimating and purchasing the material. Once cubic yard contains 27 cubic feet.
Because concrete is a fluid when it arrives at the construction site there must be allowance made for form work to contain the concrete. If you are using a pier foundation the form work will consist of a Sonotube and Sonotube base forming the spread footing. A spread footing is typically taken off as a piece and labeled on a per unit basis. In the case of a ConStructure with an incorporated locking device to anchor the ISBU you should incorporate a template for embedding the twist lock that fits into the base of the ISBU.
When considering your concrete cost you will also need to consider the distance the concrete will need to be moved once on site. Concrete poured directly from the chute is cheapest while utilizing a wheelbarrow or a pumper to move the material will add to your labor costs.
Masonry includes brick, block, glass block, or stone. Common concrete blocks are referred to as concrete masonry units or CMUs. CMUs are mainly used for walls and partitions that will support a structural load. CMUs can be utilized as a perimeter foundation for ISBU construction. Estimating masonry work requires consideration of the following factors; type of material used depth and width of joints, reinforcement requirements, bonding pattern and finally a consideration for waste. Since mortar is the bonding agent in masonry the takeoffs must also include a calculation for this. The mortar requirements will be in direct proportion to the number of masonry units used.
Since masonry is composed of modular units you start with calculating the number of masonry units needed. This can easily be accomplished on a small residential project by simply counting, or take the square foot area and divide by the size of your masonry unit. A concrete blo.ck is typically 8” high x 16” long x 4”,6”, 8” ,10”, or 12” wide for estimating purposes. The actual dimensions are 3/8” less to allow for a mortar joint. Typical waste allowance is 4%.
It's most unlikely that your plans will require you to break down your container to the component steel pieces it is manufactured from unless your building department is dead set on denying your project. The metals section should be reserved for ancillary metal pieces that are not a part of the shipping container, such as the the structural tubes (TS) that you will use to support cantilevered sections of your design, attachment plates that are located atop your foundation piers ,etc.
The metals schedule will designate each metal shape and its ASTM designation, the plan and detail drawings will show how they are incorporated with the shipping container or engineered unit.
Each shape on your metal schedule will have a prefix letter and numbers, which provide key information about each individual piece of steel. The letter designates the shape of the piece as in the chart below. The first number refers to the actual or nominal depth in inches of the section. The second number refers to the weight per linear foot of the section, in pounds per linear foot.
This division deals with the various elements used in the rough wood construction, including engineered trusses, interior wall framing, etc. Measuring lumber utilizes the “board foot” measurement, which is a piece of lumber 1” thick by 1’ square. Calculating the board feet in any piece of lumber is calculated by thickness x width x length divided by 12 times the quantity of pieces.
Check you plan for interior wall framing, roof trusses and any other rough lumber needed. You can list them on the schedule as units if you wish, such as 100 - 2x4x8 Douglas fir for interior walls. Be sure to remember that all finished lengths must be rounded up to the standard stock size available.
Finish carpentry work such as window casing, baseboards and other finish pieces can be listed as linear feet. Cabinetry and casework are listed by the individual piece. Separate them by form, function, and size.
Plastics would include counter tops and other materials that aren’t wood or metal.
Insulation to protect against hot and cold as well as vapor barriers to prevent the condensation are important elements of you home design. Insulation can be blankets or rolls called batts and are installed between interior drywall and exterior steel walls. Some batts have a foil facing that that acts as a vapor barrier. Polyethylene sheeting in 4 or 6-mil thickness is another vapor barrier alternative. Vapor barriers are applied to the warm side of the wall or roof.
Taking off insulation and vapor barriers is done on a square foot basis. If you are using loose fill insulation such as mineral wool use square foot per inch of thickness and extend it to cubic feet.
Also included in this section is the exterior siding. Use your architectural wall sections and exterior elevations to takeoff the square footage needed. Accessories such as inside and outside corners, as well as various hardware must be included along with labor costs.
Metal roof systems of pre-formed metal are most easily adapted to shipping container designs. They are available in long lengths of various shapes and widths. They can be made of steel or aluminum or even fiberglass. Preformed roofs are installed according to manufacturer’s recommendations as to the minimum pitch required.
Roof material takeoff is by the square foot while the trim pieces, and the linear foot does sealant materials.
Flashing consists of the pieces of sheet metal used to seal and protect joints from leaks. The flashing can be exposed or concealed and is utilized not just in the roofing but is also found around doors and windows. Flashing is taken off by the linear foot for materials less that 12” in width, flashing materials wider than 12” can be taken off by the square foot. List by metal type, size, application and thickness.
This division will include windows, interior and exterior doors and frames, finish hardware, garage doors, and glass and glazing. Also list hardware such as hinges, lock sets and thresholds.
The location, size, quantity and specific information concerning each individual item will be obtained from the architectural drawings. The plan view and elevation view will provide the necessary information on the location and operation of each door and window. The type and operation of specific doors or windows may be expanded upon in detail drawings.
Door and Window Schedules are a part of the Architectural drawings. These schedules list the vital info concerning each item including the rough opening size. Window Schedules are laid out in much the same manner.
Doors can be specified as pre hung, which is a complete package of a finished door on a frame, complete with trim and hardware. Doors generally fall in two categories, solid-core or hollow-core. Solid core doors provide more sound insulation, better fire resistance and dimensional stability and therefore are usually specified for exterior applications. Hollow core doors are used for interior applications.
Pre hung door units are taken off by the unit and listed according to size, thickness and composition. Sliding glass doors are also taken off as a unit which includes the entire assembly of doors, track and hardware. They can be listed by manufacturers number or by size (width x height).
Storefront glass is specified as metal framework, which encloses fixed or operable windows or doors. Each individual component should be taken off individually, the framework by the linear foot, and the glass and/or insulated panels by the square foot.
Finishes include the various interior items such as drywall, tile, acoustical ceilings, flooring and paint. These items will be shown in the architectural drawings. The quantities will be determined from the floor plans and interior elevations and sometimes-ceiling plans. The finish specifications should show the specific materials as well as the method of application.
Drywall can be taken off as a complete taped and finished system. Including all components and is quantified by the square foot of surface area to be covered, extend these measurements to the number of sheets required. Joint compound quantities can be determined by manufacturer’s coverage specifications. Tape quantities are determined by linear feet needed converted to a quantity of rolls. Screws are calculated as approx. 1 screw per square foot.
Flooring materials can include tile, carpet or wood. Tile and wood estimates are taken off by the square foot, while carpet is taken off by the square yard. Separate your materials by type, size and thickness.
Painting takeoffs will be broken down to exterior and interior applications. Further breakdown into field and trim work and separate materials accordingly by the square foot for field work and linear foot for trim work.
Mechanical systems will include plumbing systems, heating ventilating and air conditioning (HVAC). The accurate estimating of these systems may require specialized knowledge beyond the realm of the general contractor or owner/builder.
The work to be taken off will be located in the mechanical drawings pages of your plans and labeled with the prefixes M for mechanical, P for plumbing, and H or HVAC for the heating, ventilation and AC. Plumbing work requires special knowledge and a license to perform the work as well as separate permits and inspections.
Review your plumbing drawings in plan view and he riser diagrams to determiner your piping quantities. The fixture and equipment schedules are helpful in determining the quantity and types of plumbing fixtures and other equipment. The fixtures include items like water closets (toilets), shower stalls, bathtubs and lavatories.
Valves, faucets, and drains need to be included. Each fixture and it’s trim items should be listed by type, manufacturer, model and color. Equipment such as water heaters, garbage disposals, etc. also need to be included.
Sanitary waste piping and venting need to be broken down to the individual units and listed according to size and type along with additional items such as pipe hangers and supports.
Another piping system that needs to be broken down into units and listed by type and size are the natural gas lines which will distribute the gas to water heaters, stoves and clothes dryers.
Ductwork for HVAC is also a part of the mechanical systems along with the insulation that usually accompanies them. Don’t forget the various fittings such as reducers, collars and dampers. Registers, grilles, thermostats and other assorted items will need to be listed as individual units as well. For most residential it is often left to the individual pumbing or HVAC contractor to design and install a system that will meet code and perform as expected.
This division will include the various systems that distribute electricity for power and lighting.
Like plumbing, the electrical system will require special knowledge and a license to perform the work as well as separate permits and inspections. The takeoff data will be located on your electrical plans.
Raceways are used to distribute the wires that supply your power, including electrical metal tubing, flex tubing and junction boxes. Wire, flex, and cables are taken off by the linear foot.
The wire within the conduit is determined by multiplying the number of conduits by the linear foot length of these conduits. Wire should be listed by type, size and application usually allowing a 10% waste factor.
Lighting fixtures are counted as units and listed by manufacturer, model, color, and finish. List interior and exterior fixtures separately.
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