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frequently asked questions

Roof Trusses
Room-in-Roof Trusses
Metal Web Joists
Spandrel Panels

Roof Trusses

What are the different types of roof trusses?

Roof trusses can come in all shapes and sizes and Scotts Timber Engineering are able to design and manufacture as per the customer’s requirements.

The most common types of roof trusses include: fink trusses, king post trusses, raised tie trusses and attic trusses (also known as a room-in-roof trusses).

For other types of roof trusses please see our ‘Types of Roof Trusses’ page

How much do roof trusses cost?

There is no one price for roof trusses as there are a number of factors which can affect the cost of trusses. These include:

  • The type of roof truss
  • Span
  • Pitch
  • Quantity of trusses
  • Type of timber

For a quote on your roof trusses, please get in touch with the Scotts Timber Engineering team.

What is the difference between a rafter and a truss?

Both rafters and roof trusses are installed to support a roof. They are both assembled prior to being installed onto the roof of a house. However, roof trusses are assembled in an offsite manufacturing facility, whereas rafters are assembled at the construction site. Also, roof trusses incorporate internal webs for additional support and strength and form the ceiling of the roof. Lastly, rafters are more costly than roof trusses.

Are trusses cheaper than rafters?

As roof trusses are prefabricated in a controlled offsite factory they are much faster and cheaper to install than rafters. Roof trusses reduce labour costs and the need for highly-skilled labour, which is required when installing rafters.

What is the maximum span for roof trusses?

All roof trusses Scotts Timber Engineering design are bespoke to the customer’s needs. We have manufactured trusses with a span of 16 metres. Additionally, transportation of the delivery needs to be considered and therefore limits the span of the truss.

Our Design Team are able to provide advice on this and assist you with your requirements. Get in contact with our team today.

How far apart should roof trusses be?

The distance between your roof trusses, when installing, depends on the number of roof trusses. However, most are spaced up to 24 inches, or 600mm, apart.

How to safely unload roof trusses?

The unloading of roof trusses on site is the responsibility of the contractor and sufficient and suitable resources must be prepared prior to delivery to ensure the safe unloading of trusses.

For further details please see our ‘Delivery and Installation of Roof Trusses’ page

How to safely install roof trusses?

Installing roof trusses is a dangerous job as it requires working at height. Therefore, it is vital for contractors to have the right assessments completed and develop a safety method statement before any work commences.

For more information please read our blog – ‘How to safely install roof trusses at height’.

Common roof truss terms you’ll need to know

Below are some of the terms and phrases used when referring to roof trusses. Take a look at our glossary highlighting all of the most common terms used and what they mean.

Apex/Peak

The uppermost point of a truss.

Attic truss

A truss which forms the top storey of a dwelling, but allows the area to be habitable by leaving it free of internal web members. This will be compensated by larger timber sizes elsewhere.

Bracing

This can be temporary, stability or wind bracing. See these terms in our full glossary

Ceiling tie (Bottom chord) 

The lowest member of a truss, usually horizontal, which carries the ceiling construction, and to which storage loads and water tanks are applied.

Eaves

The line where the rafter meets the wall.

Gable end

The end wall, which is parallel to the trusses and extends upwards vertically to the rafters.

Girder truss

Two or more trussed rafters fixed together, designed to act as a single structural unit carrying exceptional loads such as those imposed by other trussed rafters fixed to it.

Hip end

An alternative to a gable end where the end wall finishes at the same height as the adjacent walls. The roof inclines from the end wall, usually (but not always) at the same pitch as the main trusses.

Nailplate

Metal plate having integral teeth punched from the plate material. It is used for joining timber in one plane with no overlap. It will have an accreditation certificate and will be manufactured, usually, from galvanised steel.

Pitch

The angle of the rafter to the horizontal measured in degrees.

Rafter

The uppermost member of a truss which normally carries the roof covering.

Span

Span over wallplates is the distance between the outside edges of the two supporting wallplates. This is usualy the overall length of the ceiling tie (bottom chord).

Strap

Metal component designed to fix trusses and wallplate to walls.

Wallplate

A timber member laid along the length of the load bearing walls to support the trusses.

Webs

Timber members that connect the rafters and the ceiling tie together, forming triangular patterns which transmit the forces between them.


Room-in-Roof Trusses

What is a room-in-roof truss?

A room-in-roof truss, also known as an attic truss, is a common type of truss used to add another floor and living space without needing to change the footprint of a house.

Attic trusses can serve as both a structural roof and floor in a single component. This type of truss can provide extra storage space, such as an attic/loft, or can be utilised as an extra room in the house.

Scotts’ room-in-roof trusses are designed bespoke for each customer and can offer additional living space of up to 65%.

Are room-in-roof trusses more expensive?

Yes. Room-in-roof trusses are typically dearer than other types of trusses. This is because an attic truss commonly is used to add another floor to a home and therefore the truss has a larger span which requires bigger depths of timber, thus increasing the cost of the truss.

How far can Scotts Timber Engineering attic trusses span?

We have supplied large span trusses bespoke to your requirements…

However, incorporating easi-joist® members into the design of an attic truss enables us to design a larger spanned truss; the additional strength of the metal web joist enables a larger clear span.

How much are attic roof trusses?

Attic roof trusses are commonly the most expensive type of truss to buy. This is due to the need for larger timbers as the truss has to be strong enough to support a load bearing floor.

The cost of attic trusses is determined by the span, pitch, the quantity required and the type of timber used. Additional factors to consider is the need for openings such as a stairwell, dormers or a roof light, as these features can also impact on the overall cost.

For more information about our room-in-roof trusses visit our room-in-roof trusses page, or contact our team for a quote.

Can my attic truss support a floor?

Yes. An attic truss is designed with both the structural roof and floor in one component to accommodate the need of an extra level. The bottom chord of an attic truss uses larger timber sections to support a load bearing floor.

We can also design and manufacture attic trusses incorporating easi-joist® members as the bottom chord of the truss, allowing for the easy installation of services and insulation.


Metal Web Joists (easi-joists®)

What are easi-joists®?

We design and manufacture easi-joist® members which are parallel lengths of timber plated together with Wolf Systems’ patented, precision engineered metal webs, EP 1 985 774 A1.

easi-joists®, also known as metal web floor joists, offer a lightweight and strong solution for large spanning buildings. Compared to traditional timber joists, easi-joists® can offer excellent versatility when designing floors, roofs, or even walls.

For more information about our easi-joists® visit our Metal Web Joists page, or contact our team for a quote.

What is the maximum span for engineered floor joists?

easi-joists® are a beneficial flooring solution as they can span up to large lengths due to Wolf Systems’ precision engineered metal webs.

We can design and manufacture easi-joists® with larger spans, to your requirements, but certain factors do need to be considered when installing your joists such as the type of support you have in place, etc. We can offer you advice on what is needed for larger spanned metal web joists. Contact our team today.

Are metal web floor joists better?

Metal web floors joists can add a number of benefits to commercial and domestic builds.

  • The open web design allows for easier installation of services, pipes and insulation
  • Reduces installation time and costs
  • Reduces health and safety risks on site as manufactured in an off-site controlled factory environment
  • They are strong but lightweight so can be easily handled on site
  • Designed and manufactured for heavier load requirements
  • They can span greater distances compared to traditional timber joists.

Additionally, the easi-joist® system incorporates fewer webs and up to 20% less timber.

How much do easi-joists® cost?

The cost of an easi-joist® system is determined by the number of joists required, the span and joist depth.

For a metal web joists quote contact our team.

Can metal web joists be used for roofs?

Metal web joist can be used for roofs (easi-rafters®) as well as floors and even walls (easi-panel®). easi-joists® may be positioned at any angle between zero and 90 degrees.

Our easi-rafter® roof systems can be easily adapted to create pitched roof structures which are lighter and more thermally efficient.

easi-rafters® are easier to manoeuvre on site and are safer to handle than traditional heavier timbers. The easi-rafter® system can be installed onto a wallplate or ridge beam without the need for bevelled wallplates or special metalwork items.

Common metal web joist terms you'll need to know

Take a look at our glossary of terms for the most common words used for metal web joists. 


Spandrel Panels

What is a spandrel panel?

Spandrel panels are off-site manufactured structural panels which are used as a separating wall or as an external gable wall panel, replacing the need for masonry walls. There are two types: gable and party wall spandrel panels.

The panels are designed to comply with structural, thermal and fire resistance performance standards and current building standards and regulations.

Find out more information on our spandrel panel page, or contact our team for a quote.

What is the difference between a gable and party wall spandrel panel?

Gable wall spandrel panels provide an alternative to the inner leaf of an exterior masonry wall at the gable end of a building. This type of spandrel panel must resist wind loads acting on the gable end walls and any loads imposed by the outer layers of cladding.

Party wall spandrel panels are used between two properties and are cladded on either sides of the timber frame. Party walls are required to provide a minimum of 60 minutes fire protection and should meet the sound insulation requirements outlined in the latest building regulations and Robust Details®.

Both types of spandrel panels must comply with structural, thermal and fire resistance performance standards and current building standards and regulations.

How do you unload spandrel panels safely?

Spandrel panels can be safely unloaded using either a forklift or a crane. We can provide these documents upon request.

How do you handle spandrel panels on site?

Spandrel panels should only be manoeuvred using mechanical handling. Additionally, a site-specific risk assessment and method statements for site handling, crane lifting and safe installation of gable wall panels, must be completed by the installers and contractors on site.

If storage is required, the panels must be stored in an upright position only, supported by bearers to keep the panels off the ground, and they must be safely restrained to prevent injury. Furthermore, panels should be adequately protected from adverse weather, as this can prevent bowing or wrapping of the panel.

How to install gable wall panels?

We can provide documents about the safe handling and installation of spandrel panels upon request.


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