Roof trusses are pre-fabricated, triangulated wood structures which are built in a factory and carefully designed to carry the load of a home’s roof to the outside walls. They are then shipped to the construction site and installed using a crane after the home’s walls have been framed.

Ask most builders today and they will tell you that engineered roof trusses are the only way to go and are far better than the old roof frames. The primary benefits of using pre-fabricated roof trusses are cost savings and construction speed.

The flexibility in the roof design and complexity that roof trusses enable have also made them increasingly popular. With today’s home styles, more complex roof designs, angles, cross gables and other features have added cost, which can be at least partially offset by using pre-manufactured roof trusses rather than building a roof frame on site.

The Advantages of Pre-manufactured Roof Trusses

While the basic advantages have been mentioned above, a more detailed list of the advantages of roof trusses in building a home include:

• Professional design and fabrication techniques; in conventional roof building, the carpenters build a roof frame, leaving much to chance and the builder’s opinion in terms of the roof’s strength. By comparison, a trussed roof system is designed by engineers to accommodate the specific roof design and meet building codes and enabling a more uniform size and roof pitch.
• Higher quality materials and strength; roof trusses are fabricated inside a shop, where the materials are not exposed to inclement weather or moisture conditions.
• Trusses can typically be installed in a single day, speeding the home construction process and getting the structure closed up sooner, which helps prevent moisture and other weather elements from getting inside.
• Trusses are cheaper than conventional roof framing due to labor savings and since they are built from shorter lengths of 2×4 lumber rather than the large size lumber required in building rafters and ceiling joists.
• Roof truss systems allow for almost any custom roof design and shape imaginable, allowing features such as cross gables and cathedral ceilings without being prohibitively expensive.
• Roof trusses can span much longer distances without the need for load bearing interior walls

The only real disadvantage of roof trusses is that the homeowner ends up with less usable space in the attic area; a very small price to pay!

Types of Roof Trusses Used in Building Homes

Two basic types of roof truss designs are used in home building; the pitched or common truss and the parallel chord or flat truss.

A common truss is recognizable by its triangular shape and is most often used in roof construction. Most often, variations of the common truss are named for their web configuration, such as the King Post, Fan, Fink and Howe trusses, with the chord size and web configuration typically being determined by the load, span and spacing.

A parallel chord or flat truss is so named for its parallel top and bottom chords and is often used to construct floors.

There are many roof truss types and variations including Arch Frame, Belgian, Bowstring, Dropped Chord, Gambrel, Hip Step-down, Howe, Parallel Chord, Pratt Bottom Chord, Pratt Top Chord, Raised Heel, Scissor, Semi Howe, Slope Frame and Warren.

Each type of roof truss offers pros and cons and is designed to suit specific structural and aesthetic purposes. It is important to understand the different types of roof trusses when designing a new home, doing major remodeling or a room addition. This will help match the look and function of your home’s roof to the correct roof truss type and design.

Both aesthetic and functional considerations are required in choosing the best type of truss to use for a given roof shape, size and design complexity. You will want to discuss all of these factors with your architect and roof truss engineer before ordering roof trusses for any new home or major remodeling project.

Climate is another consideration, since each type of roof truss has different characteristics that make it more or less desirable in terms of the insulation and air-vapor barrier.

We have expanded on the advantages and disadvantages of several of the major types of roof trusses:

A Raised Heel Truss is designed to span an area and provide adequate space for full depth attic insulation. While enabling greater energy efficiency, Raised Heel Trusses also enable an air tight vapor barrier to reduce problems arising due to condensation, dry rot and mold. It is also more expensive than other types of roof trusses due to the need for soffit siding, higher manufacturing cost and the additional insulation required.

A Dropped Chord Truss has two segments; a convention truss, with a secondary chord truss suspended below to help reduce truss uplift, which is when an interior ceiling may “lift upward” and result in ceiling and wall damage. A Dropped Chord truss design enables a vapor barrier and full depth attic insulation, as with a Raised Heel design. Taller studs and additional blocking and siding are required where walls and ceilings intersect in order to accommodate the air-vapor barrier, which adds to the construction cost.

A Scissor Truss also uses lower chords, but instead of being horizontal, the lower chords are sloped inward to form a shape that looks somewhat like a hang glider. Cathedral ceilings many times require Scissor Trusses and eliminate the need to use a bearing beam and wall. Insulating the attic area is more difficult with this type of truss and manufacturing costs are typically higher than other roof truss types.

A Parallel Chord Truss may also be used with cathedral ceilings, but allows for fuller and easier installation of insulation of the attic area. Because it requires steel braces and several wood products to manufacture, the cost is higher and thermal bridging caused by the steel braces can decrease energy efficiency.

Ordering Roof Trusses For Home Construction

It is very important that you specify the correct type, measurements and other factors when ordering roof trusses. Common mistakes include inaccurate specifications and failing to inspect the roof trusses when they are delivered to the construction site.

A list of the basic specification required when ordering roof trusses includes:

• Truss Span – specifies how long the bottom chord needs to be.
• Overhang Length – specifies the horizontal distance between the end of the bottom chord and the bottom edge of the top chord.
• Number of Trusses – specifies how many trusses are required. The uniform spacing of roof trusses (usually either 24 inches or 48 inches on center) makes this relatively easy to calculate.
• Design Load – specifies both the live and dead loads of the top and bottom chords, as well as wind and any other loads to which the trusses will be subjected.
• End Cut – specifies the plumb or square cut and any custom specifications
• Heel Height – specifies the vertical distance between the bottom of the bottom chord and the top of the top chord.
• Roof Slope – specifies the vertical rise in inches per each 12 inch horizontal run.
• Bearing Width – specifies the requirements for the truss bearing.
• Type of Truss – specifies the type of truss required.
• Overall Height – specifies the total vertical distance from highest point of top chord or peak to the bottom edge of the lowest bottom chord, not including the overhang.

Concrete forms offer the same wind and fire resistance, but also offer an additional built in layers of foam insulation.

Homes built with insulated concrete forms offer homeowners greater energy efficiency and less noise pollution from outside.

An insulated concrete form is basically a form for poured concrete walls that stays in place as a permanent part of the wall assembly.

The forms, made of foam insulation or other insulating material, are either pre-formed interlocking blocks or separate panels connected with plastic or metal ties.

The left-in-place forms not only provide a continuous insulation and sound barrier, but also provides a backing for drywall on the inside, and stucco, lap siding or brick on the outside.

Within these two basic ICF types, individual systems can vary in their design:

• "Flat" systems yield a continuous thickness of concrete, like a conventionally poured wall.
• The wall produced by "grid" systems has a waffle pattern where the concrete is thicker at some points than others.
• "Post and beam" systems have just that – discrete horizontal and vertical columns of concrete that are completely encapsulated in foam insulation.

Whatever their differences, all Insulated concrete form systems are engineer-designed, code-accepted and field-proven.

Energy savings and comfort are built into every ICF system. ICF’s start with a high R-Value. Four inches of ASTM C 578 polystyrene foam insulation, combine with a five inch concrete wall a typical ICF system – are rated above R-17 at 75o mean test temperature. Other insulating form configurations and materials also exhibit high R-values.

The concrete walls of an ICF home have high thermal mass, which buffers the interior of a home from the extremes of outdoor temperature during every 24-hour cycle. This reduces both peak and total heating and cooling loads.

This combination of high R-values and high thermal mass is believed to account for the amazing 25% to 50% energy savings of ICF versus wood or steel-framed homes.

In sound transmission tests, ICF walls allowed less than one-third as much sound to pass through as do ordinary frame walls filled with fiberglass. With double-glazed windows in ICF walls and beefed-up roof insulation, you will rarely hear street noises or airport traffic.

The high-mass walls of an ICF home not only give it a remarkably solid feel, but they also make it safer for the family. And make it a remarkably solid and secure investment, too. Concrete homes have a proven track record of withstanding the ravages of hurricanes, tornadoes and fires, when all the stick-build houses around them are in ruins.

In fire wall tests, ICFs stood exposure to intense flame without structural failure longer than did common frame walls. The polystyrene foam used in most ICF forms is treated so it will not support combustion. Also, tests show that its tendency to transmit an outside flame source is less than that of most wood products.

A Healthier Home & Environment

Building with ICFs is healthier for the environment in a number of ways: by minimizing the number of different building products involved in construction, by reducing the amount of waste generated on the construction site, and by lowering energy requirements for heating and cooling.

ICF homes provide a healthy indoor environment, too. Nothing held within or ordinarily emitted by an ICF wall is toxic. The measurement of the air contents of actual ICF houses shows an almost complete absence of any emissions.

Building a foundation is not usually considered a do it yourself project, but it can be done with a little advice from your contractor or a friend who has experience.

But, if you plan ahead and study a little on the specifics involved with building a concrete foundation, you can do the project yourself and save considerable expense.

If you are building a foundation for the first time, a project like an outbuilding, perhaps a detached garage or workshop is a wiser choice than a complex major project like the foundation for a new house.

Concrete Foundation Designs

Typically, foundations will be of either a shallow or deep design.

A shallow design foundation will be set about three feet into the soil. A spread footing design is typical, with concrete pads extending below the frost line, and transfers load from the walls to the earth.

Another type of shallow foundation used is the slab-on-grade design, which transfers load to the earth through a slab of concrete. Slabs also allow for the use of radiant heating.

A deep foundation is generally more complex and will be used in cases when soil conditions are poor (such as a hillside for example) or the structure must be raised to prevent flooding if the structure is being built in a flood zone.

A deep foundation transfers load from the structure through a weak top soil layer down into a stronger layer. Several variations for deep foundation designs can be used and naming conventions tend to vary, but include caissons, piers, piles, drilled shafts, and earth-stabilized columns.

Deep foundations can be made from steel, wood, reinforced or pre-tensioned concrete. A deep foundation penetrates the bedrock in some cases, so an engineering expert is definitely needed!

This article is concerned primarily with planning and building shallow design foundations used in constructing a garage, workshop or outbuilding.

Planning Your Foundation

Laying a foundation requires good planning, adherence to local code, and careful consideration of how you will be using the finished structure. If you plan on adding features like a filtered drainage system and radiant floor heating, these will need to be installed during construction of the foundation.

Don’t forget you will have to have inspections from city or county officials throughout the process, so be sure to follow your local inspection codes, obtaining the correct permits and any required soils, engineering and/or seismic reports before you begin your project.

A garage foundation is typically constructed of concrete block or a poured concrete wall. First, clear, scrape and level your building site. Next dig trenches below grade for your footings. Be sure to follow local building code regulations.

Setting Footings

Footings should be approximately two feet in width, with an extra two feet on both sides so that you have plenty of work space, which means your trenches will have a total width of six feet.

Use 2×10 boards to build forms for the footings. The forms will be removed after your concrete sets. Be sure to mark center wall lines so that you know where the wall forms will be placed.

The size of your structure will determine the height of foundation walls. A structure like a one story garage needs at least an eight inch tall foundation wall. For a two story structure, you will need at least a 10 inch high foundation wall. Again, check local codes to make sure you will pass inspection!

Steel rebar reinforcement is critical to making sure your foundation can bear wall stress adequately. Mechanical vibration is then needed in order to consolidate the concrete and eliminate air pockets or voids that could compromise or weaken the concrete’s integrity.

Install anchor bolts in your foundation, which will be used to secure walls to the foundation later. The number and location of anchor bolts needed is also set by local building codes. If appropriate to the use of the structure you are building and local climate conditions, insulation can also be added to the exterior of your walls.

Concrete Slab Pouring

After completing your footings and pouring concrete to form the foundation walls, you will be ready to pour the concrete slab inside the frame of your foundation for the floor of your garage or workshop. A layer of sand or gravel is needed before you pour the slab.

Install a vapor barrier over the gravel or sand before you pour the concrete slab. This will help prevent any moisture from rising into your slab. In some locations where moisture is prevalent, a vapor barrier below the sand or gravel may also be needed.

Place wire mesh in the center of your slab and rebar in the footing areas to increase rigidity and prevent any cracks in the concrete.

Local code sets your specifications, including slab thickness, footing thickness, footing width, what size wire mesh is needed, how thick a layer of sand or gravel is needed, the size and placement of rebar and the placement of foundation anchors or bolts. Again, be absolutely sure to follow your local building code before planning your foundation specifications, setting forms and ordering materials.

Foundation anchors are embedded in the wet concrete to later secure walls firmly to your foundation; you don’t want the walls falling off your foundation in the case of an earthquake or high winds!

Installing Drainage and Radiant Heating

A nice feature to add to your garage slab is a center drain for washing a car, boat etc.

Drainage pipes and radiant heat tubes should be placed and attached to the wire mesh before pouring your concrete slab. The slab should be pitched from the back towards the front of your garage for proper drainage.
There are some features to your garage or workshop you will not be able to add after your foundation is complete, so decide up front during the planning phase which features like a drain or radiant heating you will include in the foundation.

Radiant heating is a nice, efficient heating system to use in a workshop or garage, since you get heat without any need for blowers or air movement, which helps make for a more dust free environment. Also, the floor will be nice and warm for those occasions when mechanical projects require you to sit, kneel or lie on the floor!

Adding a drain may also be worth considering. In some cases, a garage or workshop drain simply uses drywell drainage; you just dig a hole and fill it with a course stone for water to drain into. Drainage pipe will be placed on the foundation bed and the drain placed before concrete is poured.

Alternatively, a connection to your sewage system may be required for your drainage system. Local codes are usually quite strict about what you can dump in garage drains. A filtering system can also be installed to keep any contaminants from entering the soil or sewer system.

Sill Sealers and Concrete Sealers

You will also want to seal your garage or workshop to inhibit moisture, cold or hot air, and particles. There are two commonly used types of sealers; floor sealers and sill sealers. The sealers are normally applied during the construction to help keep your garage or workshop dry and well insulated.

Sill sealers use adhesive foam and the application will sit between the top of the foundation and sill plate, creating a waterproof barrier.

A sill sealer will conform to the surface of your foundation to prevent any cracks or gaps that could otherwise form between the foundation and sill plate as the concrete shrinks as it cures. Sill sealer applications have a strong adhesive on one side that will stick to your foundation. This does a great job of protecting against moisture, air, rodents, insects, etc.

Typically, concrete sealers are spray on applications designed to prevent moisture and vapor from rising up through concrete, which is porous. Concrete sealers can provide other benefits as well, including preventing radon gas seepage and inhibiting the growth of mildew or molds. Concrete sealers can also help strengthen concrete and prevent cracks over time.

You should always get advice from a professional when planning a foundation to be sure it is all engineered correctly for the intended structure it will support and to be sure it meets all local building codes!

Step by step video on preparing your concrete foundation:

If you do live in a hurricane zone, you should definitely install hurricane shutters. Hurricane shutters protect your home from extreme damaging winds.

These winds throw debris against your house at speeds exceeding 90 miles per hour. In particular, you want to prevent window breakage.

Your goal is to keep the wind outside. If high winds get inside your home or business, it becomes trapped. In reality, the pressure from wind continues to build as it stays in a structure. This can literally cause the winds to blow your house or business apart.

Some experts recommend install hurricane shutters if you live in an area that experiences tornadoes or other extreme high-wind weather. The problem with this is that tornados will literally lift a roof off a house, or a house off its foundation without ever blowing out a window! So while they can help prevent window breakage from flying debris, in reality it does little to fully protect your home. However, protecting your home is worth the investment.

If windows are broken during storms, you are likely to have water damage to rooms. This is expensive and time consuming to repair. More importantly, damage to irreplaceable family heirlooms and other invaluable items are not always reparable.

Hurricane shutters come in a wide variety of styles, including automatic ones that you lower with a touch of a button! Other styles include ones you manually close. Either type is easier and more time efficient that nailing plywood to your windows hours before the storm hit!