Preventing Dampness


The paint on the walls is peeling off, have you seen that? What’s that wet spot under the sill doing there? You have painted the walls numerous times, but the paint continues chipping. Perhaps you have finally decided to take the plunge and get the opinion of a damp-proof expert. Knowing if the damp proof expert was giving you accurate information would be a good idea. Not understanding the basic principles of damp proofing could result in a costly and time-consuming misstep.

Here, we’ll glance at the basics of damp proofing, including what to check for and the various damp proofing goods and systems that can help you.

First, we’ll have to figure out where and what’s generating the dampness on the job. We can save money on a professional’s visit by eliminating the most evident causes of moisture before calling them.

What causes high-level or remote damp walls? Is the moist spot causing severe problems inside? Look for water dripping down the wall, perhaps from condensation or a leaking toilet overflow line. A damp spot or salts showing through can signify that water from the continual source against your brickwork has been dragged into your inside finishes. It’s probably pretty apparent that you need to stop doing this right now, and once you have, redecorating your moist wall will be a breeze. If you fix the external source of moisture, such as a leaking gutter or downpipe, the problem should go away. Structural flaws, such as damp walls, can also cause water infiltration into your home. This is trickier to determine, but here are several considerations: Repairing any lead flashings around chimneys or under windows, repairing any cracks in the walls (may require structural repair; consult engineer), fixing any defective pointing (could be a significant problem; seek professional advice), replacing any loose tiles (obviously a source of dampness in the structure immediately), and preventing any bridging of a cavity wall with rubble are all urgent needs.

Except for the cavity wall bridging, those above may be visually inspected for dampness. Still, a chartered surveyor’s comprehensive report could be a valuable additional check.

Condensation mold due to inadequate ventilation is another potential issue. Condensation issues, which look like black patches and are sometimes hidden under cabinets or in corners, are often misunderstood as increasing dampness. Again, ventilation is best left to the professionals, and newer buildings that are required to be more airtight have fewer windows. As with structural flaws, a professional surveyor should be able to steer you in the proper direction here.

The absence of a damp-proof course or the presence of high ground levels over the top of your current damp-proof course are the two most common causes of a failed damp-proof diagnostic. If your property’s outside ground level is too high, you may experience problems beyond just damp walls, including, in the worst case, water seepage into your home. If you can’t dig it out, you’ll have to treat it like a basement and waterproof it.

Now that we know better where the damp could be coming from, we can examine “how to damp proof” using the newfound information.

A damp proof course is described. What should I do if my property is broken or doesn’t have one?

This should be established as the first step in any “how to damp proof” tutorial, what to do if you don’t have a damp proof course, and whether or not you have one. Above internal floor levels, inserted into the mortar course 150 mm above exterior ground level, is the damp proof course, or dpc, a physical barrier made of slate in older buildings or a happy or HDPE membrane in later buildings. This dpc prevents rising dampness (water that moves upward from the earth) from entering the building during construction.

If your dpc is broken or nonexistent, you’ll need to repair it or install a cavity drain membrane to prevent and remove moisture buildup inside your home. The dpc can be reinstalled in one of two ways: cutting it into the mortar course and replacing it with slate packing (a process best left to the few with the necessary expertise) or inserting a chemical dpc. A damp-proofing expert is the person to call when you need a dpc installed. To insert, you drill holes on the exterior of your home, typically 20 centimeters apart, to a depth sufficient for your wall, and then inject a damp-proof liquid or cream to build a barrier that prevents dampness movement. Thanks to technological advancements, Dpc creams are a safer bet than other liquids; nonetheless, you should only have a qualified professional install them. Injecting creams or liquids is a dirty process that requires “hacking off” damp plaster to a height typically 1.2 m before injection and then re-plastering with a salt retardant component in the mix to prevent the salts from coming through. The wet trades and waiting periods before redecorating are the true issues here. The effectiveness of various damp proofing techniques varies. Therefore, discussing this with the contractor doing the work is essential.

Another method of damp proofing is to install a cavity drain membrane. These membranes can be finished with either a smooth plaster or a plasterboard surface. Unlike the cream option, this barrier is physically attached inside the wall, allowing it to “breathe” and release any moisture that has built up. So it’s not just a line across the mortar joints; it forms a barrier over the entire region it covers. Outside, you can use this damp-proofing substance to stop water from infiltrating via porous brickwork or faulty mortar courses. Dimple thickness can range from 3mm to 8mm on commercially available cavity drain membranes. These chemicals are comprehensive in preventing moisture damage to interior finishes and require little to no surface preparation or drying time after application. However, for the interest of the home as a whole, you should locate the cause of the moist walls (such as broken gutters).

I’m hoping you’ve learned enough to get started on “how to damp proof” now. You have a lot of tools at your disposal; all you need is expert guidance and a reliable contractor to help you choose the best one.

Warren Muschialli is a John Newton & Company director focusing on basement waterproofing, damp proofing, and pumping. Warren has extensive expertise advising clients on damp proofing and recommending the most effective basement waterproofing solutions [].

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