Engineered floor joists, such as easi-joists (metal web joists), are becoming increasingly popular in the UK, replacing traditional solid timber joists and concrete flooring.

It is the role of the Building Designer to provide Scotts Designer with the correct information on which the floor design will be based. Keep reading to find out the necessary information required.

1. The building footprint and layout

To start, the Designer will require a basic dimensioned plan of the building footprint. This is used as a framework to create the floor design.

2. The joist span, direction and floor depth available

One benefit of metal web joists is their ability to span greater clear spans than traditional solid timber joists, allowing the Designer better flexibility for room layout. Additionally, the most important benefit is its ability to facilitate quick and easy installation of services and pipes.

Easi-joists, when used for flooring, are laid perpendicular to load-bearing walls. However, other configurations can be possible when required to suit openings or other construction details.

Metal web joists are available in a range of sizes and are manufactured in our offsite factory in Thrapston to your exact project requirements. It is important to note, the length of joists can be limited by the practicality of handling and transportation.

3. Design dead load or details of types and weights of floor and ceiling coverings

It is important to make the Designer aware of the correct loadings at the design stage. This will ensure a safe, effective and cost-effective floor design. Additionally, the Designer should also be aware of any unusual loads that may be applied to the floor system, e.g. spa baths, snooker table, hoists, etc.

Using the latest design technology by Wolf Systems, the Designer can accommodate both dead and imposed loads applicable to the use and occupancy of the building.

4. Intended building use and design-imposed loads

Metal web joists can be used for floors as well as flat and pitched roofs. In both circumstances, easi-joists provides the Designer with greater design flexibility.

5. Position and weight of non-load bearing internal partitions

Each individual design is dependent on the application and loads applied. Metal web joists are not designed to support masonry load-bearing walls but can be designed to support lightweight partition walls.

6. Other additional loads

If significant loads are added to the building, such as hoists in care homes and adapted living accommodation, it is important this information be provided as early as possible in the design stage.

7. The positions and method of support at all bearing position

Metal web joists can be designed to be supported on either the bottom or top chord and can be built into supporting elements or connected via joist hangers, whether for masonry or timber frame projects.

8. Any special requirements for floor members

This includes specific chord widths, joist spacing or deflection requirements. Floor vibrations or deflection limits should always be discussed with our Designer. Where the span exceeds four metres a strongback is normally used to dampen vibration. Our team can provide guidance on installation.

9. Size and location of required floor openings e.g. stairs

If openings are required, the Designer will need to know the location, size and type of opening (such as stairs) within the floor area. This is one of the most critical aspects of design in order to transfer the loads and deal with practicalities of creating the opening using trimmers and girders or multiple metal web joists.

10. Size and location of large or non-standard services planned to be run through the floor zone

As previously mentioned, one of the benefits of using metal web joists is their design ability to easily install services and utilities within the floor void area. They require no cutting, notching or drilling, speeding up the process. The depth of joists can be varied to suit particular duct requirements, please inform our Designer of this in the design stage.

11. Other considerations

Horizontal restraint straps

These are used to tie the walls to the floors and should be fixed to the perimeter walls in line with the Building Designer’s instructions.

Preservative treatment

Scotts metal web joists can be preservative treated if required. This is normally needed where the environment is likely to be classified as Use Class 1 or 2, as defined in Eurocode 5.

Fire and acoustics

Our engineered floor joists fully comply with all the relevant standards in relation to fire and acoustics. Please refer to the Robust Details’ handbook for more details.

 

If you require any further information or advice, our expert Designers are available to answer any of your questions. Contact the team on 01832 732366 or email info@scottsofthrapston.co.uk

To find out more information about metal web joists, take a look at the TRA’s Buyer’s Guide to Metal Web Joists.