Constructing a Blockwork Wall

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Although a wood-framed partition is easy to build, it does not provide the most effective sound insulation and it will need extra strengthening if it is to carry shelves or cabinets. In situations such as this, a partition built from lightweight concrete blocks is much more suitable. However, you cannot build such a partition on an upper floor, since even a reinforced concrete floor is unlikely to be strong enough to carry the load of a concrete block partition. A concrete first floor makes an ideal foundation and even a suspended wood first floor will do if a full-width wood sole plate is put down first, but check with your local Code.

Before starting work, the floor, walls and ceiling should be stripped of all coverings and any coving and base cut away with a chisel to clear the blocks. The easiest way to mark the position of the partition is

with a chalked plumbline, snapping it against the floor to leave two parallel chalk lines the width of the blocks. Continue these lines up the walls and across the ceiling making sure they are vertical.

For strength, it is best to tie the partition to adjacent walls by cutting recesses in them to accept the end blocks of alternate courses or similarly by using galvanized metal ties screwed to the walls and buried in the blockwork mortar joints. Nailing a guide batten to the wall against one of the chalk lines is also a good idea to help with the alignment.

Trowel a 6in wide layer of mortar (1 part masonry cement: 6 parts soft sand) across the floor to span the chalk lines on it, leveling it out to about 1/2 an inch thick. Then scribe a guide line through the mortar in line with the chalk marks on the end walls, using the point of your trowel and a long straight-edged plank.

There are many different types of concrete block to choose from, but the best types for building an internal partition are known as aerated blocks (A).

These are light in weight, so they are easy to handle — an important quality since they are twice the size of a normal brick. This fact also means that you can build a full-height partition relatively quickly. You can drill them, knock nails into them or, using a general-purpose saw, cut channels in them (B) to conceal electric cables and pipe work. Sound will not pass through them as easily as it would a woodframed partition, nor will heat.

Aerated blocks should be laid in the same manner as bricks in a “stretcher” bond pattern with mortar joints. Their normal size is 17 x 81/2 x 4in. For finishing, you can either plaster them directly or nail on battens and fix a gypsum board cladding to the battens.

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