How heavy are they ?

As the weight of the webs is negligible, timber is the main element. Timber density is also significant.
For a 72mm wide joist, approximately 4.5kg/m length.
For a 97mm wide joist, approximately 6kg/m length.
For a 122mm wide joist, approximately 7.5kg/m length.

Can they be modified?

Joist cannot be modified without prior permission from our design office.

Can I drill a hole through my joist?

Holes are not to be drilled through joists without prior permission from our design office. Smaller holes are generally acceptable but a generic Yes or No cannot be given.

What does strongback bridging do?

ninja quiet sumo strong spacejoist

Strongback Bridging (SB) is used as a load sharing element between the joists. When installed correctly, standing on one joist effectively spreads the load over 3 joists. As it is structural, it has to be graded timber, usually the same as what the SpaceJoist has been made from. It has to be installed in its vertical orientation, to a timber vertical either within the joist (chase vertical) or face fixed to the side of the joist. Minimum size is 35mm x 97mm TR26 but larger sections should be used on deeper joists. Using lower grade timber will have a lesser effect.

What is the minimum bearing?

Minimum bearings depend on what SpaceJoist are going into. From a practical point of view, anything less than 50mm should be avoided as it leaves little tolerance. If the joists are built into a wall with a bearing greater than 90mm, then they are deemed to provide restraint to that wall.

How do I support them?

SpaceJoist are supported in the same way as normal timber joists, when bottom chord supported. They can be built into walls or supported in hangers. If building in it is advisable to use the horn detail so air-tightness can be achieved more easily. Hangers have to be a minimum of 2/3 the depth of the joist to provide adequate top chord restraint, otherwise top chord noggins will be required.

What is the EC5 vibration check?

The EC5 vibration check allows the analysis of the joist deflection to EC5 rules, meaning they can span further providing the vibration check is satisfied. This takes the whole floor construction into account and adds together the joist, decking, plasterboard and strongback properties to see how the floor will perform under a point load, designed to represent a heel drop test.

What are Robust Details?

Robust Details are methods of construction in the UK that guarantee a level of sound attenuation between dwellings, mainly used in compartment floors (i.e. flats). Registering with Robust Details and constructing in strict accordance with their details means you can avoid sound testing, which can be expensive and time consuming. SpaceJoist are currently accredited with E-FT-3 and E-FT-6. Robust Details can only be used with timber frame, masonry construction has an issue with flanking noise.

How do I protect against fire?

Around 90% of fire resistance is provided by the plasterboard so it is important to specify this correctly. The required fire resistance for domestic floor structures is 30 minutes and for compartment floors is 60 minutes. This is generally achieved by one layer of plasterboard for 30 minutes, 2 layers for 60 minutes.

How do I join a 2-ply joist together?

Joists are to be connected together as specified by metalwork supplier’s instructions only, using the referenced connectors. Joists are connected with either OW-Clips or PSTS screws. Typically a cluster of 4 around the point load, then 600mm centres along the rest of the joist, staggered top and bottom, with two at each end as well. OW-Clips can only be used on 2-ply joists; 3 plies have to be screwed if they are to be used. Screwing positions are the same as clips.