Strong fixings for internal walls

Various types of construction of internal walls will be found in different properties; plastered masonry, stud partitions (lathe and plaster or plasterboard), plasterboard dry lined onto masonry - (our page "types of internal wall" explains these in more detail).

The type of construction will influence the method used to obtain strong fixings for brackets; each type of construction is covered separately below - plastered masonry, stud partitions, plasterboard dry lined on to masonry.

Plastered masonry walls:

Making strong fixings on to most plastered masonry walls is normally fairly straight forward using screws with appropriate wall plugs - wall bolts should be used to fix the brackets for extremely heavy loads.

The plugs and screws need to be long enough to pass through the plaster into the masonry - plaster alone does not provide enough strength to hold these types of fixings.

Also take care to avoid mortar joints between the masonry as these can be weak points especially where the mortar is lime based (generally in older properties. Try to position the plugs into the actual brick/block.

Some true concrete blocks and older bricks may contain hard pieces of flint and hard stones, these can cause a drill bit to off line - this often results in the holes not lining up with those in the brackets. One method to overcome this is to first fix a vertical batten to the wall using screws and plugs, and then fix the brackets to the batten using shorter screws.

Modern lower density, high insulation blocks are extremely soft and won't take ordinary wall plugs. With this type of block, use the special wall plugs and drill the blocks carefully to avoid making overlarge holes.

Stud partitions (both lathe and plaster and plasterboard).

Fixing for shelves should not be fixed just to plasterboard (or lathe and plaster). A strong fixings will only be obtained where brackets are directly screwed to the vertical timber framework.

The vertical timbers are usually spaced at equal distances apart - on older stud partitions they are normally about 405mm (16 inches) apart, while more modern stud walls have them spaced at about 600mm (24 inches).

Finding the position of the vertical timbers is not always easy, with plasterboard walls, try tapping lightly on the wall while moving sideways - at the position of the timber it should sound solid rather than the hollow sound resulting from the space between the timbers.

Finding the position of the vertical timbers behind lathe and plaster is more of a problem as there is no significant difference in the sound of a surface tap. One method to locate the timbers is to draw a horizontal line at the position for the shelf and then drill a series of small holes along the line about 25mm (1 inch) apart until the timber is found. Once the position of the first timber has been established, measure 405mm (16 inches) along the line and drill another hole to confirm the location of the next timber - if this hole does not locate the next timber, drill another horizontal series of small holes from this hole until a timber is located.

The surface of lathe and plaster walls may crack as a bracket is tightened down and the lathes are compressed. Once the positions for the screws have been determined, drill shallow clearance holes through the plaster and lathes so that it is not subjected to sideways pressure when the screws are tightened.

Plasterboard dry lined on to masonry walls.

Plasterboard dry lined on to masonry walls is probably the most difficult type of wall to get a strong fixing on as the surface plasterboard is only attached by 'blobs' of plasterboard adhesive. If wall plugs are fitted into the masonry and the bracket screwed down onto the plasterboard, the surface will deform.

One practical option is to:

• Establish the positions for the wall fixings.
• Cut holes in the plasterboard at these points - the holes should, if possible, be smaller than the back of the bracket.
• Make up a spacer for each bracket position to fit in the holes in the plasterboard - the spacer should be as thick as the distance from the masonry behind the plasterboard and the front face of the plasterboard.
• The brackets can be fixed to the wall either by using screws through clearance holes drilled in the spacer into plugs in the masonry, or by first screwing the spacer to the masonry and then using shorter screws to fix the bracket to the front of the spacer.

The holes in the plasterboard and the spacers should be smaller than the back of the brackets so that they are covered by the brackets when they are tightened down.

Modern lower density, high insulation blocks are extremely soft and won't take ordinary wall plugs, so if the masonry behind the plasterboard is of this type, use the special wall plugs and drill the blocks carefully to avoid making overlarge holes.