Check for recommended guidelines within your country which outline heights, angles and positioning in relation to grab rails within the home. Every country usually has its own set of standards. If you are unsure you can contact your Occupational Therapist to get information on the standards (link how to contact an OT).
Some examples of guidelines include:
1) The general recommended diameter of a grab rail is between 3 and 5cm
2) If a grab bar is horizontally mounted it should have a wall clearance of 4.5cm (Canada) or 6cm (Australia) to ensure the person will not catch their arm in the gap between the wall and the bar.
3) The person installing the grab rail must ensure that there is no possibility of any of metal part of a rail coming in contact with electrical cables. All metal grab rails need to be earthed to prevent electrical accidents.
Invest in a trained professional
When installing the grab bar it is important to have these rails installed by a trained professional who can see the structure of the building and will know the best, most secure place for the rail to be attached. The wall on which the rail will be fixed can also impact on the location. If the studs are at either end of the shower and you want to install a rail in the middle of the wall then the builder/installer may have to reinforce the wall. Or you can consider another option such as mounting a rail from ceiling to the floor.
General Guidelines are:
Brick/Cement Wall. Rails can be attached safely in any position.
Timber Frame Wall: Rails must be fixed at each end to the wooden studs.
Metal Frame Wall: Rails must be fixed at the ends of each metal studs.