Another popular frame type for domestic buildings are the brick and block style frame. In fact, 70% of all UK new self-build are built with this traditional technique. Brick and block work houses use a cavity wall construction with an inner skin made of blocks and an outer made of bricks, with cavity ties linking the two walls and the cavity filled with insulation. Key to the strength of the system are the structures internal walls that help bear the weight of the upper floor. With this method the external wall goes up first, to first floor then the internal load bearing walls, followed by timber joists or a concrete floor.