What is Flitch Beam? | Advantages & Uses of Flitch Beam | How Far Can You Span with Flitch Beams?
What is Flitch Beam? |Advantages and Disadvantages of Flitch Beams | Uses of Flitch Beam | How Far Can You Span with Flitch Beams?
What is Flitch Beam?
A flitch beam (or flitched beam) is a type of composite beam that is commonly used in the construction of houses, decks, and other wood-frame constructions.
The flitch beam is typically composed of a vertical steel plate placed between two wood beams, with the three layers secured together with bolts. It is sometimes referred to as a steel flitch beam in that prevalent form.
Additional alternating layers of wood and steel can be utilized to create a stronger beam. The metal plates included within the beam are referred to as flitch plates.
Flitch beams were employed to strengthen long-span hardwood beams at a low cost, but have since been mostly replaced by more modern technologies.
Flitch beam reduces fluctuations in timber performance and allows wide openings, such as garage doors, to be spanned while keeping lintel depth to an acceptable minimum.
Each beam is manufactured to design and can be cambered to meet the needs of the application.
Uses of Flitch Beam
Flitch beams are presently primarily used in traditional renovations to reinforce old lumber supports or for aesthetic purposes when exposed beams with the appearance of wood and the strength of steel are required.
In the United Kingdom, converting stables into offices necessitated cutting the beam holding the floor down its full length and inserting a similarly sized steel plate.
The resulting flitched beam was then fixed with glue and bolts, which preserved the look while adding strength. In a two-story new construction, flitch beams were employed as columns. The second floor and roof were supported by glulam beams.
This gave the look of wooden columns while still giving the essential strength.
The transformed-section method is used to calculate the size of a flitch beam that will be used in construction.
The steel beam component is considered to be an equivalently flexible (but considerably thicker) piece of wood. The elasticity of the entire beam can thus be estimated as if it were totally constituted of wood.
A flitch beam can span up to 25 feet long before it needs support from another beam. One way to make sure your home’s roof will be structurally sound is by installing flitches on top of each other with supports at regular intervals between them
How a Flitch Beam Works
A flitch beam is composed of two layers of wood sandwiched by a steel plate (the flitch plate).
The resulting beam has the same strength as a solid wood beam but less depth (vertical dimension); less weight than a steel beam of the same strength and dimensions; and may be attached using wood frame fasteners.
The wood side pieces offer lateral support to the narrow steel flitch plate and prevent it from buckling.
The structural load is distributed proportionally to the relative stiffness of the steel plate and the wood side pieces in a flitch plate beam.
Transformed section characteristics, which consider the composite section as an equivalent wood element, are utilized to structurally assess a flitch plate beam.
Benefits of Flitch Beams
The main benefit of using steel flitch beams is that they are lighter and cheaper than pure steel, while also still allowing the builder to fix in surrounding timber framework using either nails or screws.
This would save the builder money, while ensuring the strength of their work project is not compromised in any way.
Flitch beams can also be made stronger, by adding more timber and steel layers into the design.
Flitch beams are also stronger than timber, and require less depth for building than a wooden beam would, if it had the same amount of strength.
Flitch Plate Bolting
Adequate bolting is critical for flitch plate beam performance. Because the stress is applied to this composite beam via the wood side pieces, the bolts must distribute the portion of the load carried by the steel plates.
Only the wood side pieces of the beam end bearing supports rest on the supports. As a result, bolts at the beam’s ends must transfer the end reaction from the plate to the wood.
The load is transferred between the steel plate and the wood side pieces via shear through the bolts and friction between the steel and wood.
The magnitude of the weight imparted through friction is determined by the bolt tightness. Under the nuts, washers should always be utilized.
The nuts should not be tightened to the point where the wood becomes crushed beneath the bolt head or washer. The bolt tension and friction forces will decrease as the lumber seasons and shrinks.
Because of this, and because identifying the quantity of load transfer owing to friction between wood and steel cannot be determined with confidence, the bolt friction component is usually ignored in computations.
Advantages and Disadvantages of Flitch Beams
Advantages of Flitch Beams
- Flitch beams are much stronger than wood alone.
- They require less depth than a similar strength wood-only beam.
- They are significantly lighter than a comparable steel beam of the same size.
- They can still be attached to the remainder of a wooden building with nails.
- Flitch beams can also be made from existing in-situ joists or beams, making renovations easier.
Disadvantages of Flitch Beams
- The usage of this type of beam has fallen significantly due to the high costs of labor.
- With the introduction of high-strength engineered timber that uses current adhesives and lower-cost wood fibers, this technique has become essentially outdated.
- Engineered lumber is cut to length and installed in the same way as sawn lumber is.
- The flitch requires fabrication in the shop and/or field bolting.
- This, combined with the beam’s substantially higher self-weight (11.4 pounds (5.2 kg) for engineered wood vs. 25.2 pounds (11.4 kg) for a flitch beam), reduces the system’s efficiency.
Flitch Beam FAQs
How far can you span with flitch beams?
Flitch plate beams are capable of achieving greater spans and supporting higher loads than built-up wood members.
Flitch beams can span very far. A 2×12 or a 2×8 flitch beam is just as rigid as a 4×4 timber beam depending on your design.
What is the load capacity for a 2×8 flitch beam?
Flitch plate beams are composite members which combine the strength and stiffness of structural steel with the versatility of wood.
The 2×8 flitch beam has the same load capacity as a typical 4×4 timber beam.
What is a flitch plate?
A flitch plate is the steel portion of a flitch beam that is bolted onto timber beams or studs to give it extra strength and rigidity.
What is the difference between a flitch plate and a beam?
A flitch plate is used to help strengthen the long wood beam it crosses. A flitch plate is a steel plate that is sandwiched between pieces of framing lumber and bolted together.
They are used in a similar manner to built-up wood girders or headers in residential and light commercial construction. A flitch beam is produced by steel plate sandwiched steel plates between timber beam
What size of a flitch beam should I use in my house?
It depends on your project and the load that will be placed on it. The size of your flitch plate should be based on the strength you want your beam to have for that particular project.
What are some ways to use beams in your house?
The main way beams are used in homes is to span between rooms, but they can also be used to support roofs, ceilings and floors.
Unlike engineered wood beams, flitch plate beams can be flush framed with dimension lumber joists without causing shrinkage related distortions to the structure.
What kind of wood is best for a flitch beam?
2×6 Beams are recommended for use in Flitch Beams as they are more rigid and have greater strength than 4×4 beams. It is advisable to use timber that is already pre-seasoned before the build as this will help to prevent any rotting, which may cause problems with the beams splitting and sagging over time.
How thick should the wood beams be in a flitch beam?
In order to make the best possible flitch beam, it is advisable to use timber that is 3-4 inches thick. The thinner the timber used in a flitch beam, the weaker it will be.
Are flitch beams used in horizontal or vertical applications?
Flitch beams are typically used in horizontal applications.