Damp Proofing

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Damp Proofing in Johannesburg

Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Damp problems are one of the most frequent problems encountered in homes.

Once damp has become a problem in your building, you may begin to notice the following physical defects. Be sure to contact us to arrange your free professional damp assessment.

Damp proofing is a material that resists the passage of water with no hydro-static pressure and waterproof as a treatment that resists the passage of water under pressure. Generally damp proofing keeps moisture out of a building where vapor barriers keep interior moisture from getting into walls. Moisture resistance is not necessarily absolute: it is usually defined by a specific test method, limits, and engineering tolerances.

Damp proofing is accomplished several ways including:

• ¥A damp-proof course (DPC) is a barrier through the structure by capillary action such as through a phenomenon known as rising damp. Rising damp is the effect of water rising from the ground into your property.The damp proof course may be horizontal or vertical.^[3] A DPC layer is usually laid below all masonry walls, regardless if the wall is a load bearing wall or a partition wall.
• ¥A damp-proof membrane (DPM) is a membrane material applied to prevent moisture transmission. A common example is polyethylene sheeting laid under a concrete slab to prevent the concrete from gaining moisture through capillary action. A DPM may be used for the DPC.
• ¥Integral damp proofing in concrete involves adding materials to the concrete mix to make the concrete itself impermeable.
• ¥Surface coating with thin water proof materials for resistance to non-pressurized moisture such as rain water or a coating of cement sprayed on such as shotcrete which can resist water under pressure.^[3]
• ¥Cavity wall construction, such as rainscreen construction, is where the interior walls are separated from the exterior walls by a cavity.
• ¥Pressure grouting cracks and joints in masonry materials.^[3]

Materials

Materials widely used for damp proofing include:

• Flexible materials like butyl rubber, hot bitumen, plastic sheets, bituminous felts, sheets of lead, copper, etc.
• Semi-rigid materials like mastic asphalt
• Rigid materials like impervious bricks, stones, slates, cement mortar or cement concrete painted with bitumen, etc.
• Stones
• Mortar with waterproofing compounds
• Coarse sand layers under floors
• Continuous plastic sheets under floors

Masonry construction

A DPC is a durable, impermeable material such as slate, felt paper, metal, plastic or special engineered bricks^[6] bedded into the mortar between two courses of bricks or blocks. It can often be seen as a thin line in the mortar near ground level. To create a continuous barrier, pieces of DPC or DPM may be sealed together. In addition, the DPC may be sealed to the DPM around the outside edges of the ground floor, completely sealing the inside of the building from the damp ground around it.

In a masonry cavity wall, there is usually a DPC in both the outer and inner wall. In the outer wall it is normally 150 millimetres (5.9 in) to 200 millimetres (7.9 in) above ground level (the height of 2-3 brick courses). This allows rain to form puddles and splash up off the ground, without saturating the wall above DPC level. The wall below the DPC may become saturated in rainy weather. The DPC in the inner wall is usually below floor level, (under a suspended timber floor structure), or, with a solid concrete floor, it is usually found immediately above the floor slab so that it can be linked to the DPM under the floor slab. This enables installation of skirting boards above floor level without fear of puncturing it. Alternatively, instead of fitting separate inner and outer DPCs, it is common in commercial housebuilding to use a one-piece length of rigid plastic, (albeit an angled section), which fits neatly across the cavity and slots into both walls (a cavity tray). This method requires the need for weep vents to enable rainwater ingress to drain from the cavities otherwise rising dampness could occur from above the DPC.

Concrete walls and floors

Concrete normally allows moisture to pass through so a vertical damp proof barrier. Barriers may be a coating or membrane applied to the exterior of the concrete. The coating may be asphalt, asphalt emulsion, a thinned asphalt called cutback asphalt, or a rubber polymer.^[7] Membranes are rubberized asphalt or epdm rubber. Rubberized products perform better because concrete sometimes develops cracks and the barrier does not crack with the concrete.

There are many solutions for dealing with dampness in existing buildings, the choice of which will largely be determined by the types of dampness that are affecting the building (e.g. rising damp, hygroscopic damp, condensation, penetrating damp etc…).

Where can damp occur?

Damp typically occurs in walls, floors, doors and windows and also within pipes, plumbing, ceilings and roofs.

What are the causes of damp?

Damp is caused from moisture coming in to the building from outside, from condensation from within the building or from water being extensively used within specific areas such as bathrooms. If an area is not well ventilated, this will exacerbate the damp problem in your building.

How does damp cause damage to a building?

Damp can cause secondary damage to a building leading to peeling paint and wallpaper, as well as loose plaster. Mortar is liable to crumble as a result of damp, while steel and iron fasteners can rust.

How can I tell if I have a damp problem?

Once damp has become a problem in your building, you may begin to notice the following physical defects. Be sure to contact us to arrange your free professional damp assessment.

• Mold and wet stains on skirting boards
• Decayed or rotting timber
• Crumbling plaster
• Peeling, bubbling or flaking paint
• Discolouration, mold growth and staining on walls
• Salt stains and salt deposit buildup

Is damp in a building a risk to health?

Damp is often the perfect breeding ground for a variety of molds and fungi. Spores, airborne mold concentrations and bacteria can be inhaled by humans which can cause serious respiratory illnesses and other health problems.

What is rising damp?

Rising damp is the slow, upward spread of moisture within the lower sections of walls and other ground supported structures, and can be identified by a characteristic ‘tide mark’ along the lower portions of the wall, as well as crumbling plaster and peeling or blistering paint.[/toggle]

What is lateral or penetrating damp?

Lateral, or penetrating damp is caused by water leaking through your walls and is often the result of structural problems such as faulty guttering, roofing, flashing and cracks in the walls.

What problems does rising damp cause?

Damp proofing problems on inside walls:

• Paint does not adhere to the wall.
• Wall paper lifts and stains appear on the walls.
• Plaster flakes away, feels soft and spongy, bubbles and white powder or crystals appear.
• Skirting boards and floor boards rot.

Damp proofing problems on outside walls:

• Mortar frets and falls out between bricks and stonework.
• Stains or white powder appear on walls.

How can damp be prevented?

Regular building maintenance and good ventilation are both key to preventing damp in your building. Be sure to check your roof regularly for holes in roof sheeting, or missing tiles. Also clean gutters and check for structural damage such as cracks regularly. Keep windows open as much as possible or check that ventilation and air-conditioning systems are working as they should.

Can serious damage from damp be repaired?

Yes. SA Damp, which is a specialist waterproofing and damp proofing company, is able to provide professional, long lasting damp repair solutions. Based on an assessment of your building, which is conducted by our highly trained, knowledgeable and experienced technicians, we provide a professional damp assessment to identify the damp repair and maintenance work that will be required.

High risk structure – because such a building has been identified as one that will rot quickly and structurally fail if not up-graded and constantly monitored, our waterproofing and damp proofing plan will be designed to reduce such a building to a medium risk structure.

Medium risk structure – such a building will require an ongoing maintenance plan, which includes regular assessments and repairs to ensure that it does not degrade further.

Low risk structure – minor repairs and regular maintenance will ensure that such a structure will not begin to degrade for hundreds of years.