Damp wall insulation is complicated, but important and useful as a repair measure. Before turning to insulation, let us get acquainted with the basic masonry tools. A trowel or hawk is used for applying material (fig. 1, 1. part). Whenever possible, choose the smallest possible hawk, because constantly moving a loaded hawk places heavy strain on the wrist. A plasterer’s trowel is used for spreading and leveling the mortar (fig. 1, 2. part).
With a trowel, it is very important that the center line of the handle passes through the tip of the trowel. When choosing a trowel, preference should be given to smaller ones with a rounded tip. Wooden floaters (perdaške) are used for leveling mortar (fig. 1, 5. part). We should have floaters in as many dimensions, i.e. sizes, as possible. When choosing a mason’s hammer (fig. 1, 4. part), it is best to choose the one with a single blade, because the hammer with two blades (hammer-chisel) is used for special work, and besides that it is 1,5 times heavier than the single-blade hammer, whose weight is 0,7 kg. Other important tools are the level (fig. 1, 6. part), which should be as large as possible, the plumb bob (fig. 1, 3. part), which we can make ourselves, laths for measuring, leveling and checking, and a string. Long laths can also be used for leveling bricks, by placing the lath next to the row of laid bricks and, by striking it, bringing individual bricks into a straight line. A string is needed as a guide for laying a row of bricks, by tying the string to two laths at the ends of the wall, as well as for checking the plane of finished walls (fig. 2). Where the string moves away from the wall, the wall is recessed; where it presses against it, the wall is bulged.
Post insulation of damp walls whose plaster is already crumbling and whose paint is peeling, as we have said, is one of the most troublesome tasks and the hardest to resolve. A complete solution to this problem is very time-consuming and can be achieved only with substantial investment.
Before starting the subsequent insulation of such damp walls, we need to make sure whether it is possible to extend the insulation below the level of the building floor. If that is not possible, if the building has a concrete floor and no basement, it is pointless to start the job, because the moisture will bypass the new insulation.
For subsequent insulation, major and carefully executed masonry work is required, which means that such work requires a certain level of expertise (fig. 3, 1. part). First, it is necessary to open the wall along the desired line. This line should be above ground level, but below the level of the ground floor. Once we have determined the appropriate line, the wall plaster should be broken away on both the interior and exterior sides, and a line should be found where the brick courses are approximately horizontal. Care must be taken to locate the exact positions of various electrical and other services in the walls so that they are not accidentally damaged. Self-supporting main walls and their extensions should be insulated. Secondary walls, which are built on floors, do not need to be insulated even if they appear damp, because they can take in moisture only from the side from the main walls. By insulating the main walls, the moisture will disappear through natural drying from these secondary walls as well.
Wall openings
We begin opening the wall by removing the bricks above the selected line (fig. 3, 2. part). Around the starting brick, above, below and at the sides, we chip away the mortar, then by tapping the brick left-right and up-down, we loosen it and pull it out. After removing the first brick, the others are removed very easily. In order not to compromise the load-bearing capacity of the wall, we may open the wall over a length of one to two bricks. Opening the wall over a greater length is dangerous!
Opening walls with a width of 1,5-2 bricks, e.g. a weekend cottage, is relatively easy. A much more difficult task is opening the main walls of residential buildings, whose width is several bricks. When, during wall opening, we remove the bricks, it is advisable to place supports made of half- and quarter-bricks in their place so that no collapse occurs during the work and no hand injury is caused (fig. 3, 4. part). If we have succeeded in opening the wall completely, level the exposed surfaces of the main walls and coat them with a thick layer of insulating compound or with UB-B-55 or UB-B-65 bitumen. Onto this prepared base, then place insulating bituminous strips 15-40 cm wide, which we previously coated with bitumen. The strips should be installed so that they overlap the wall surface. If possible, insulating strips marked (fig. 3, 3. part) should be used. Above this, with rather laborious work, we should place new, completely sound and frost-resistant bricks in strong cement mortar and thus close up the opening. Above the new row of bricks and below the bricks of the old wall, mortar should be packed in with an iron rod, into which we may mix small brick fragments. In this way, proceeding along the main wall piece by piece, we will be able to carry out subsequent wall insulation.
Instead of removing, i.e. opening, the wall in this way, we can also work with a saw if the wall is made of soft stone or if the thickness of the mortar between the walls is large and lies in a horizontal plane. In this case, we break through the wall at one point and pass a wall saw through the widened opening. With the saw we can remove the rows of bricks faster, of course again in small pieces. If we slightly widen the opening made with the saw, we can also insert directly the insulating strip coated with bitumen on both sides. After complete setting, cement mortar should be packed above the bitumen. One of the insulation procedures is the electro-osmotic process.
It is known that moisture penetrates walls from the foundations upward through capillaries. This penetration is aided by the potential difference between the ground base level and the lower parts of the walls. By installing insulating electrodes, the penetration of moisture will automatically stop.
Electrodes are built into the wall above ground level and below the lower floor level for 15 cm. They are made of iron bars - reinforcing steel, with a diameter of 12-15 mm. We place them in holes drilled with a 2 cm drill bit, at a distance of 40 cm from one another. The electrodes are installed both on the inside and the outside, so that the ends of the electrodes are spaced 2-3 cm apart at the center line of the wall. After installing the electrodes, the openings should be filled with cement mortar. The ends of the electrodes projecting from the wall should be connected with steel wire 6-8 mm thick, and the steel wire to one flat iron element measuring at least 60x60x8mm that is placed below ground level. For aesthetic reasons, it is good to recess the steel wire connecting the electrodes into the wall. The elements of this installation are connected by soldering or welding. Care should be taken that the electrode and wire system does not come into contact with the electrical network or with grounding conductors. In some cases, based on local measurements, the electrode system should be assisted by connection to low-voltage direct current.
After the damp wall has been insulated, the wall is plastered, and you can read about how this is done in the article Repair and replacement of plaster