Damp Proof Injections

What are damp proof injections?

plastic dpc.jpgThe problems caused by rising damp have their root cause in the movement of groundwater, rising upwards through the masonry of your property. Modern houses have a damp proof course (DPC) or sometimes known as a damp proof membrane built into the walls just above ground level. This consists of a layer of waterproof material (generally plastic, though on some older properties slate is used) laid between courses of brickwork which acts as an impermeable barrier to moisture.

In older buildings where no DPC is fitted, or other buildings where the DPC has deteriorated or been damaged in some way, rising damp can be a serious problem. The standard treatment for this is to retrofit a DPC. Damp proofing injections are a way of injecting a remedial, liquid DPC into the masonry at the appropriate level. The liquid used permeates the base of the wall and sets to create a physical, impermeable barrier to the groundwater, keeping it from rising in the wall.

How are chemical Damp Proof Courses fitted?

DPC-Injection.jpgHoles are drilled into the wall about 150mm above external ground level but beneath the level of internal floor joists, or close to the floor if it is solid. The holes should be around 100mm apart and span the entire width of the affected wall. In cavity walls the holes will need to be drilled into both the internal and external walls. The exact spacing of your holes will depend on the individual construction of your wall and should be decided upon by a damp proofing specialist. The damp proofing chemicals are then injected into the holes where they spread out laterally forming a continuous barrier across the wall.

How do chemical Damp Proof Courses work?

Most chemicals DPCs are silicone based. It is the silicone in the formula that fills the pores in the masonry, making them resistant to water. Early chemicals required thickening agents to stop them running back out of the holes. They also relied upon high pressure machinery and their usage was often expensive, messy and prone to ‘blow backs’ and the loss of liquid via invisible cracks and fissures in the masonry.

Modern ‘second generation’ chemical DPCs come in a variety of forms such as liquids, creams and gels. These are water based and use a technology that emulsifies the product inside the wall. This makes for easier, more precise applications. They are also much more user friendly chemicals that are low odour and easier to handle. The actual type of formula required will depend on the type of problem you have and the existing state of your masonry. Triton and Dryzone are the market leaders, ask your damp proof specialist which formula is best for your own circumstances.

The very latest ‘new generation’ DPC formulae come as a water soluble thixotropic gel. This gel undergoes a chemical reaction within the wall, filling the masonry capillaries with a network of water repellent silicone resin. The result is permeable to water vapour, meaning that the wall will be able to breathe and dry out quickly and effectively.

Despite the growth in DIY damp proof injection kits, unless you are already skilled in major building works, the injection of a remedial DPC should be left to the professionals.




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