All branches & showrooms will be shut on Monday 27th May. Any online orders placed on 27th May will be picked up on Tuesday 28th May.

The complete guide to roof trusses

Do you need trusses for your build? Want to know if you can alter them? Or do you want to match-in to an existing roof? And just how many trusses will your roof need?

Here is your complete guide to roof trusses: 


What is a roof truss? 

A roof truss is an engineered, structural framework of triangulated timbers that provides support for a roof. A roof formed using trusses can use up to 40% less timber than a traditional roof – this makes them highly cost effective. 

Roof trusses are prefabricated, which saves time on-site when it comes to installing them. 

What are the different types of roof trusses? 

There are many different designs of roof trusses available, but some of the most common include: 

  • Standard Fink trusses: Mostly used by national house builders for new build homes. 
  • Mono trusses: Sloped in one direction and mostly used in porches. 
  • Scissor trusses: Looks like scissors and mostly used as a feature over living rooms, larger bedrooms etc. to create a vaulted ceiling. 
  • Gable trusses: Works as an end cap for the roof and usually used alongside other types of roof trusses. 
  • Attic trusses: Allows for extra storage or living space within the roof. 

How do roof trusses work? 

Roof trusses act much like a lid on a box. They work by transferring the weight of the roof to the load bearing walls of the house. 

What are trusses made of? 

Our trusses are made from TR26. This is a strong, specialist engineering grade of timber for trussed rafters. 

Can trusses be cut/altered? 

No, trusses cannot be cut or altered. As an engineered product built for purpose, any moderations could affect the structural integrity of the truss. 


Trusses vs rafters 

While both trusses and rafters effectively do the same job, there are some differences which make trusses more suitable for modern builds. 

Trusses are delivered to site as a full structural component – saving labour time and costs when it comes to installation. Rafters are known as a ‘cut roof’ single component which need to be assembled on-site. 

Trusses can spread the weight of a roof across a number of triangulated struts and braces, whereas Rafters have 2 main outer beams which provide the support. 

Roof Trusses vs roof rafters diagram

Can I get trusses with no overhang? 

Yes, you can get trusses with no overhang. We are seeing more buildings being designed without truss overhang to create a contemporary, minimalist look. 

Trusses can be manufactured without the overhang. 

How are trusses measured? 

Trusses are measured using span and pitch. Additional measurements will be required when needing to match an existing roof. 

How many roof trusses do I need? 

The number of trusses required for a roof depends completely on the design. However, typical roof truss spacing means that they are usually 400mm (16 inches) or 600mm (24 inches) from centre – this means from the centre of one truss to the centre or the next truss. 

What truss profile is best for my build? 

This all depends on your designs and requirements. Profiles will be designed to dissipate the roof load across various struts and braces in a way that works best for the build. 


Attic truss design - room in a roof
Trusses for attic spaces

By opting for attic trusses, you can future-proof your property by having the option of extending your living space into the roof if required.


What is an attic truss

An attic truss is a type of roof truss that has an open space at the bottom to accommodate a living space and is designed to allow for domestic floor loadings.

We can accommodate various designs based on your requirements.

Talk to us about attic trusses
Matching an existing roof - trusses for double storey extensions
Trusses for double storey extensions

If you are building a double-storey extension, you will need to match your existing roof in with the new roof on the extension. This requires the following measurements:

  • Overall span (Wall to Wall)
  • Bottom Chord Length (If different than the Wall-to-Wall Span)
  • Overhang Length
  • Heel Height
  • Peak Height
  • Pitch/Slope of Roof

Need to match an existing roof? We can come to site to measure and provide accurately-measured trusses.

Talk to us about trusses for extensions

Roof trusses from below

Talk to us about roof trusses

Need some roof trusses for your project?

Whether you’re building from scratch or matching into an existing roof, we can supply roof trusses bespoke to your measurements.

Send us your contact details, your location and some information about your project and a member of our engineered timber team will come back to you.

Please note: we only supply trusses in the South of England.

Find out more about engineered timber at Elliotts

Share :

Call us for expert help and advice - 023 8038 5300. Lines open 9am - 5pm Monday to Saturday