You may know them as either tensions traps or bat straps. Whatever you know them as, they are necessary for the restraint of floor and roof structures to walls. This is usually to stop bulging or cracking of walls, with the most common cause being repeated wind pressure. However, having proper vertical and horizontal restraint straps in place will stop this issue.
What is the worst that can happen in the absence of proper restraint straps?
There are, of course, degrees of severity with regard to the problems that can arise from inadequately fitted straps, but just take a look at the video in this link to see just what can happen in the absence of proper, or indeed any lateral straps. In this video, you will see the entire roof gable collapse on top of a car. With a lucky pedestrian just yards away, this was a narrow escape from potential disaster. As you can see it was quite a strong wind, from the tree bending over, but obviously, this is no excuse for what was clearly a construction error in a new build property. Obviously, this is an extreme example, but it should be more than enough to persuade any negligent builders to ensure that the proper restraints are in place.
Types of restraint straps
Depending on the exact implementation, type of building, level of exposure, and other environmental conditions, different straps can be deployed. As a general rule, heavy-duty restraints are fitted in roof rafters, trusses and joists that are tied into masonry walls, while light-duty restraints are best deployed for vertical loads, such as wall plates on top of masonry walls. In the case of the above video, it looks like neither were fitted.
Restraint strap best practice
As with anything in construction, there is no use doing the right thing, wrongly. There are several key factors to consider when deploying restraint straps to ensure they will do the job as intended.
Regulations surrounding restraint straps
Concerning all floor and roof construction, walls must be given lateral restraint straps as laid down by provisions in BS EN 1996-2:2006 and Building Regulation requirements. There is a requirement for lateral restraint straps at floor, rafter and flat roof member levels. For pitched roofs, straps will be required at ceiling joist levels.
If the video shows anything, it is that any construction work should involve Building Control inspectors and structural engineers. They will make sure that best practice is followed and any work carried out will not leave any structural weaknesses.