Plastered Hollow Brick and Cable Trellis Systems

Houses made of plastered hollow brick started being built around 1930. These bricks can accomodate all trellis cable systems from FassadenGrün almost without restriction. However, certain problem areas should be avoided, and with very thick or special plasters, difficulties can sometimes arise. Here you will find relevant detailed information, including drilling tips and some of the history and characteristics of hollow block bricks. Hollow brick or clinker without plaster are discussed under exposed masonry.


Properties of plastered hollow masonry

Since about 1930 bricks were not only massively produced as solid bricks but also with holes as 'perforated bricks.' Initially this was done to save material and to lower costs during firing, but it also served to 'interlock' the stones better when laying on the mortar layer. Expect to find hollow brick masonry in most structures built after 1930. After about 1950 there were also plastered hollow blocks of concrete, some of which were filled or foamed. Later, 'insulation' became the new factor: bricks with holes allow significantly less heat to escape from the house as solid bricks do. The hollow bricks were continuously optimised and now consist of 'more holes than stone.' With a trick, the insulation values ​​are increased even further: additives such as sawdust or the like are added to the clay during the kneading process, which burn off when the shaped bricks are fired, leaving porous hollow spaces in the already thin webs of the brick-- among these, 'Poroton' stones ('porous clay') are particularly well known. There are aslo bricks where the hollow chambers are filled with foam or  insulating material.

Today, hollow bricks are generally divided into those with a dense structure or a porous structure. The latter have less strength in the webs. The degree of porosity is difficult to see from the outside of the brick; the weight of the bricks will let you know!

Exception: double-leaf masonry

In exceptional cases, plastered hollow bricks are used as the outer 'leaf' (wall) of a 'sandwich' ('hollow' / two-walled) facade. Behind a 10 cm thick hollow brick wall is an empty or insulating space about 10 cm in front of the actual load-bearing wall. Such facades are to be considered as weatherboard (the non load-bearing wall of two leaf masonry) and special care taken when mounting cable trellis systems.

Problem Zones

If your windows have roll-down blinds, do not drill into the area where they are mounted above the window; in general, avoid mounting above windows (lintels) and in the area of ​​ceilings or floors, ring anchors, and wall-integrated supports. Sometimes these elements are made of concrete and slightly offset to the rear, then insulated and clad flush with the wall with special sandwich bricks before the final plaster is uniformly applied, thus avoiding thermal bridges at the level of the concrete elements. In some places or (with older buildings) also on larger surfaces, it is possible to find thermal insulation (4-6 cm) directly on the masonry. In this case it will be impossible to affix a cable system or espalier direclty with the standard trellis mounts/fittings. These places are invisible after the plaster has been applied; they can be found by gently tapping the wall before drilling. These places are not really visible on plaster, but are recognizable by light tapping and listening before starting to drill. *Special plasters more than 2 cm thick can also be problematic.

Cable Systems for Hollow Masonry

Basically, all wire rope trellis systems from FassadenGrün are suitable here, but our Massive version with WM 12153 can only be used within limits, especially in very light vertically perforated bricks where the load-bearing capacity of the stone material is so limited. In the above-mentioned problem zones, the cross mount WM 12XX2 might be necessary too. If plastic rawlplugs, like the DH 10065 are used, choose a size larger for hollow brick masonry.

Drilling into Hollow Brick

Such walls are easy to drill into. All drill types can be used. The above-mentioned insulated zones should not be drilled into or at least treated separately;they can be identified by knocking lightly on the wall before drilling. Hollow bricks with a high proportion of holes / 'air chambers' (Poroton') should generally be drilled without the hammer/impact function; otherwise chipping is likely in the narrow webs and the load-bearing capacity of the mounting decreases drastically. So, pre-drill with a smaller drill bit. Problems can occur when drilling in border areas of the webs-- the hole often 'runs away' and becomes crooked. This can be corrected by drilling and gluing the mount (plug) using composite mortar. Please refer to our general information on drilling.