The Difference Between Rising and Penetrating Damp

Having a room in your house susceptible to condensation can cause major issues with dampness. Besides the unsightly mildew caused by it, dampness comes with other concerns. Prolonged exposure to a damp room could cause you and your family serious health issues such as respiratory problems, respiratory infections, allergies or asthma. Damp and mould can also affect the immune system. Furthermore, not repaired in time, dampness can have financial repercussions

Not all dampness is the same, so before you begin to repair, first identify what type of dampness it is.

A metal damp-proof course
A metal damp-proof course. Image by wdwd [GFDL or CC BY-SA 3.0 ], from Wikimedia Commons

Rising Damp

As the name suggests, rising damp is caused from the ground up causing a wall or a floor to soak up water. It’s inevitable that the exterior walls of a house will be exposed to wetness due to rain and wet weather. This will usually be averted with a damp-proof course or a damp-proof membrane.

As per the NHBRC’s Guide to Home Building Manual, it has become standard regulation for modern buildings to be built with damp-proofing courses, however, some older buildings may still not have them. It’s also possible that over time, they may have worn out. Something else to note is that you could experience problems if the ground level outside your home is higher than the damp-proof course.

Rising damp
Image by Kebabknight [CC BY-SA 4.0 ], from Wikimedia Commons

How to Identify Rising Damp

  • Check for damaged and/or rotting plaster or skirting boards (if fitted).
  • Peeling paint is a tell-tale sign of a potential problem.
  • If fitted, check the wallpaper for peeling and/or wet patches.
  • A white powder-like substance, much like salt may appear encrusted on an affected wall. This is caused by the wall soaking up salts from the ground.
  • Check for lifts in floor tiles or coverings.
  • Wet-stain patches are signs that water was once present, even if the area is dry when you check.

How to Treat Rising Damp

If you’ve inspected and discovered that the damp has been caused by a blocked cavity wall, either unblock it or hire a professional.

If for some reason your house has no damp-proof course, or if it is damaged, definitely have this installed. It is made of waterproof materials which curb further rising of damp.

Penetrating Damp

When water either leaks or absorbs through walls, this is referred to as “penetrating damp”. Unlike rising damp, when the dampness expands, it will usually be in a horizontal direction. Incorrectly installed or faulty guttering and pipes are a common culprit but cracks in the walls, ceilings or roofs could also be the cause. As you can see, there are many reasons this could occur, so thorough inspection is necessary in order to prevent structural problems.

Defective Pointing
Defective pointing can allow rain to penetrate through masonry walls. Image by Kebabknight [CC BY-SA 4.0 ], from Wikimedia Commons

How to Identify Penetrating Damp

  • Wet walls and patches are clear signs that dampness is seeping through your walls.
  • Check your ceilings for dark patches. Ones that grow bigger over time are especially a concern.
  • Wet and cracking plaster.
  • Dampness may not always occur where visible. Keep an eye out for dripping or condensation at the edge of cupboards and other furniture that may be blocking a wall.
  • A buildup of mildew or mould inside built-in cupboards.
  • It goes without saying to check for puddles.

How to Treat Penetrating Damp

Sometimes treating dampness may be easier than identifying it. It is imperative that you find the source of the problem in order to prevent an unnecessary waste of time and money. Simply repainting a wall will cause you issues if the source of the leak is not fixed. In most cases, simply fixing the cause of dampness is enough. This could include:

  • Resealing window and door frames,
  • Fixing damaged guttering,
  • Re-plastering cracked walls
  • Re-cementing spaces between bricks and masonry in the event that the cement has crumbled,
  • Applying a water-repellent coating
  • Check for obstructions within the cavity wall which may be feeding water from the exterior to the interior.

If you’ve discovered penetrating damp below ground-level (in the foundation) of your building, you may need to call an expert as this involves a professional survey of the buildings construction and materials.

Need Help With Damp-Proofing and Waterproofing?

At AmanziProofing, we pride ourselves on our many years of experience in construction and building maintenance, with waterproofing and damp-proofing being our primary focus. If you need assistance, please feel free to contact us.

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