Simple Building Calculator

Simple Building Calculator

Functions to estimate material amounts for a stick-built building from the bottom (footers and foundation) up through framing, siding and roofing.  This is useful for a cabin, tiny-house or even a backyard shed.  The functions include the following:

Summary Function

• Building or Shed Materials: Computes the top (roof) to bottom (deck) framing and roofing materials needed for a simple building based on a few dimension. 

Roofing Functions:

• Gable Roof Area: Computes the total surface area of a roof, the number of 4x8s, the number of bundles of shingles and the number of roofing nails needed for a roof based on the length, span, pitch and overhang.
• Trusses Needed for Roof: Computes the number of trusses needed for a roof based on the ridge length and truss spacing.
• Rafters for Gable Roof: Computes the total number and length of rafter boards (roof joists) for a gabled roof based on the ridge length, pitch and span.  It also returns the length of the ridge board, and the length and number of rafter ties and collar ties.
• Purlins for Gable Roof: Computes the total number and length of purlins for a simple gable roof based on the ridge length of the roof, the roof pitch and the span of the roof.
• 4x8 Sheathing for Gable Roof: Computes the total surface area of a roof, the number of 4x8s and framing nails needed for a gabled roof based on the length, span, pitch and overhang. 

Siding Functions:

• Siding for Rectangular Wall:  Computes the siding materials for a rectangular wall (squared corners) for horizontal panels or boards based on the dimensions of the wall and the panels or boards.
• Siding for Gable End: Computes the siding materials (horizontal panels or boards) for a wall under a gable roof end, based on the dimensions of the wall and the panels or boards.
• Metal Siding for Gable Ends: Computes the number of vertical panels for a wall under a gable roofline.  It also returns the total area of gable end wall, number of screws needed and the cut angle of the panels.

Framing Functions:

• Plate Boards for Room: Computes the number of top and bottom plate boards, above and below the studs, required for a room based on the length of the four walls and whether the top plate is doubled or single.
• Studs for a Room: Computes the number of stud boards required to frame a room based on the length of the four walls, including extra studs at the corners where the walls meet.
• Drywall for a Room: Computes the number of drywall sheets (4x8 or 4x12) required to cover a walls and ceiling of a rectangular room based on the length and height of the walls.
• Drywall for Wall: Computes the number of drywall sheets (4x8 or 4x12) required to cover a wall based on the length and height of the wall.
• House Sheathing: Computes the number of 4x8 sheets (e.g., OSB or T1-11) needed to cover the exterior walls of a basic structure with gable ends.  For more siding options, see the Siding Calc.
• House Wrap: Computes the square feet of house wrap needed for a basic structure with gable ends.
• Subfloor 4x8 Sheets: Computes the number of 4x8 sheets (e.g., plywood or OSB) required for a floor, sub-floor or deck.
• Floor Joist Count: Computes the number and length of joists (joists and end plates) required for a floor or deck based on the dimension of the room or deck and the on-center joist separation.  It also includes the number of joist hangers.
• Foundation Sill Plates: Computes the number of sill plate boards to connect a foundation to the first deck.

Foundation and Basement Functions:

• Concrete in a Slab:  This computes the volume of concrete needed for a slab. The volume is returned in cubic yard and equivalent amount by number of bags (40lb, 60lb, 80lb).  It also return the area of the slab and the length of forms that might be needed.
• Blocks for Foundation:  This computes the number of blocks needed for a foundation based on the foundation dimensions and the size of the blocks.
• Concrete Needed for Foundation:  This computes the amount of concrete needed in a poured concrete foundation based on the dimensions of the foundation. It also returns the square feet and number of 4x8s needed for the forms.
• Concrete for Footers:  This computes the amount of concrete needed in a footer based on the dimensions of the footer.

DIY and Pro Construction collection of calculators and data support the main categories of calculator supporting construction. 

SUBCATEGORIES

• Roofing and Siding: Shingles, underlayment, roofing nails, metal roofing panels, screws, underlayment and more.
• Framing: Studs, plates, joists, trusses, sheathing, decks, walls, and more.
• Masonry: Concrete, brick, block, rebar and more.
• Rough-in Construction: Plumbing, electrical, cable and conduit, HVAC, insulation and more.
• Finishing: Paint, wallpaper, flooring of all kinds, ceiling tile and more.
• Outdoors: Landscaping, gardening, mulch, lawn care, retention walls and more.

Construction Math

The Simple Building Calculator includes formulas in three groups (Roof - Frame - Foundation) that roughly correspond to three distinct components and phases in the development of a building.

Roof Equations

The ROOF group has equations associated with roofing, including the count and cost of rafters,  roofing plywood, and shingles.  The shingle equations includes price estimates based on shingle price point observations from national providers like Lowes and Home Depot.  The unit prices used here are based on a vCalc data repository of pricing (Shingle Pricing).

Frame Equations

The FRAME group has the most functions.   These functions include those related to the count and cost of floor joists, sub-floor boards, wall studs, and drywall.  For anything above a simple one room structure, you will have to develop your estimates room-by-room.  The cost data comes from vCalc's tables (see list below) which come from the nationally advertised prices and are updated approximately every two months.

Foundation Equations

Starting from the bottom and going up, the Foundation functions include calculations for the amount of concrete needed for a footer, and then the amount of materials (concrete or block) needed for the foundation walls. And then finally, the amount of concrete needed to pour a slab in the basement to complete the rough construction. These formulas are are all based on the dimensions of the building.  However, the block count estimator is based on standard block sizes in the U.S.

Usage

The basic construction of a building is the same for many structures.  With few exceptions, a building requires a foundation or peers, a frame and a roof.  Many buildings have basements that are below grade or partially below grade and these are typically made of block, poured concrete in forms or stone in order to stand up to exposure to the earth.   Foundations are often coated with moisture blocking substances (e.g. tar), and perforated piping is often laid in a gravel bed, outside of the base of the foundation and covered by a silt barrier (paper) to drain water away from the base of the foundation in a French drain. The frame of the house is built on this foundation, and in the modern era, the frame is physically attached (bolted) to the foundation.  This last step is widely performed to keep a house on its foundation during earth quakes.  The boards that are bolted to the foundation are generally referred to a foundation sill plates and are used to affix (nail, screw or bolt) the deck and joists for the first level of the building frame, to the foundation.

The first part of the wood frame is the deck of the first floor.  The deck typically has side boards (skirts) that are vertically placed around the foundation with joists running across the span and nailed into the skirts at the ends or affixed to the skirts via joist hangers.  The end of the joists rest on the plate and have a direct conveyance of their load (weight) through the solid plate to the foundation.  In some cases, when the span of the basement is too great, a beam is erected mid-span for the joists to convey their load in a third place (both ends and on the beam).  The architectural design should account for this.  Beams must rest on part of the foundation and/or on post (molly columns) that rest on concrete peers comparable to the footers of the foundation.

The frame of a building can have several floors, multiple rooms and each room can have doorways and windows, not to mention many built-in features (e.g. closets).  Between rooms are passages and hallways and between floors are stairs.  But the basic framing of walls and floor is consistent in most structures.  Between floors you will find decks that are made of joists that are roughly surfaced with sub-flooring.  Joists are either strong pieces of lumber like 2x12's or I-joist made of composite materials or even steel. The span of the joists and their separation are greatly dependent on the structural load that they will have to bear, but there are some industry standards (e.g. 16" separation).   When the spans of joists over rooms are too great, beams are required.  Nonetheless, the framing of the building is primarily composed of the walls (interior and exterior).  These walls separate the rooms and carry the load (weight) of the floors and roof above.  Walls come in many categories including:

• interior
• exterior
• load bearing
• non-load bearing

It is common that load-bearing walls have a double top board (plate).  However, some non-load bearing wall can have a single plate on the top. Interior walls are typically covered with drywall or paneling to enclose things like wiring, plumbing and cable conduits and to provide a surface for fine finishes.  

Exterior walls are typically strengthened with structural panels such as plywood, have wind braces (diagonal steel) and are covered by a vapor barrier to keep the difference in moister (outside to inside) from leaching into the housing materials.  Exterior walls are also used to attach the outermost surface of the house (brick fascia or siding) to the frame.  The exterior surface may be  siding or even masonry  (brick or stone).  In the latter case, attachments are connected to the exterior wall and integrated into the masonry seams (mortar joints) as the exterior facing is laid.

All exterior walls are load bearing, which means they carry more weight than that which is directly above them.  The weight they bear includes the load of floors that span open spaces and then rest on the load bearing walls.  These walls typically have standard spacing of vertical members (16" centered studs) and doubled top plates to provide strength between the studs.  It is important for the architect of the building to methodically transfer the weight of every component of a building through every load bearing component down to the foundation and ensure adequate strength is built into the design and materials to carry the load for the life of the building.  This all sounds complicated, but some wonderfully simple buildings exist and are still strong after centuries.

Above the frame of a building is the roof.   The attic which is formed by the roof frame on top of the house is typically the location of the greatest layer of thermal insulation such as fiberglass.  The roof serves the primary purpose of shielding the frame of the house from the water of rain and snow above and of carrying the load of snow (in some climates) until it melts.   Roofs have load bearing structures, either rafters or trusses that convey the weight of the roof to load bearing walls (e.g. outer walls).  Plywood or purlins are attached to the surface of the roof frame as a base for the final roofing material.  The most common roofing material is the shingle which is nailed in layers on plywood.  However, there are numerous other roofing materials from thatch, to tile to standing-seam metal. 

External Links

• Menards
• Home Depot
• Lowes