When constructing floors and roofs it is important to bear in mind that they provide lateral support to walls.

So when it comes to floors and joists being ‘built in’ or where walls require lateral restraint straps, do you know what to look out for?

Here are some best practise tips to make sure your lateral restraints are in check.

Where floors and joists are “built in” or supported by hangers off the wall the following should be taken into account:

  • Shrinkage of joists – members must be secure to prevent twisting.
  • Joists should be protected against moisture.
  • Gaps formed in the wall construction should be sealed with a compressible filler to ensure air tightness.

The bearings of all floors, joists and roof members must not be less than 90mm onto a load bearing wall.

When are lateral restraint straps required?

At floor and roof constructions, walls require lateral restraint by tension straps in accordance with the provisions in BS EN 1996-2:2006 and Building Regulation requirements.

Lateral restraint straps are required at floor and rafter or flat roof member levels. If you are building a pitched roof you will also need to use straps at ceiling joist levels. Provision is necessary, should the height of the wall exceed recommended values found in BS EN 1995-1-1:2004 and current Building Regulations.

Best practise of lateral restraint straps

  • Ensure all restraint straps fit tightly against the masonry face within the cavity.
  • Use blocking in the gap between the joist / rafter and the parallel wall at all lateral restraint strap positions as well as in between joist / rafters for the length of strap required.
  • Lateral restraint straps at floor or roof level must not be retro fitted by plug and screwing the strap to the masonry.
  • Restraint straps must turn down the cavity by at least 100mm and be tight against the face of the wall.

Timber floor / wall detail

Suspended concrete beam and block floor / wall detail

Rafter / gable wall detail

For more information please refer to our Technical Manual and check out our blog on how to use lateral restraints during construction.

By Frzana Ferguson