The 7 Most Common Causes of Rising Damp in Houses

You may be surprised to learn that the most common cause of rising damp in houses is not the failure of the damp proof course (DPC). The truth is that damp proof course failure is rare, with some estimates suggesting that only 1 in 10 properties diagnosed with rising damp actually have a failed damp proof course. Properties built before 1875 won’t have a damp proof course and many traditional and period properties will not have have one by design.

Diagrams Of Rising Damp Causes

The 7 most common causes of rising damp are shown below in 3d model diagrams which should clearly illustrate the potential pathways of moisture. If you have been told that the property needs a damp proof course injection without the rising damp surveyor ruling out these possible damp causes then proceed with caution.

High Ground Bridging Damp Proof Course

high ground bridging dpc

Over time flowerbeds become raised as gardeners add more earth or compost to the pile. Eventually with no one noticing the damp proof course becomes bridged.

High Pathway Bridging Damp Proof Course

high path bridging damp proof course

Without doubt this scenario is the most common cause of rising damp symptoms in houses. The high path shown can often be a driveway, a footpath or even wooden decking. All external ground should be installed 150mm below the damp proof course as per good building practices.

External Render Cause Of Rising Damp

render briding damp proof course cause of rising damp

This is a common cause of rising damp in houses which will not be solved by installing a chemical damp proof course. It is often totally overlooked by rising damp surveyors despite being quite an obvious issue and very easy to spot.

Pointing Causing Rising Damp

pointing as cause of rising damp in house

Pointing should never be over the top of a damp proof course as it can allow moisture to pass around it and up the wall. House builders know this so it should not be a problem, unfortunately often well meaning home owners will have the pointing re-done (probably due to a damp problem) and mistakenly cover over the damp proof course.

Blocked Cavity Cause Of Rising Damp

blocked cavity wall cause rising damp

Cavity walls work by creating a void which prevents moisture jumping across the gap to affect the internal wall. In this example the cause of the rising damp is a blocked cavity allowing the groundwater to rise up and around the damp proof course. The blockage can be caused by debris from building works above (roofing etc) falling down the gap, wall tie failure pushing material into the gap, or cavity wall insulation which has become wet due to an external defect.

Faulty Plaster Can Cause Rising Damp

plaster cause of rising damp in house

What is a skirting board for? Not a question most people consider, I mean they look nice so surely that is the point of them? Skirting boards are fitted to hide the gap between the plaster and the solid floor which should be present. Amazingly many plasterers do not know this and take the plaster all the way down to touch the solid floor. This can allow moisture within the floor to rise the plaster giving rising damp symptoms.

Floors Can Cause Rising Damp

Sometimes a floor screed laid too high can bridge over the damp proof course. This itself causes an issue by itself, however, the problem is often made even worse by laying an impermeable, non breathing, covering on the floor such as vinyl or even a liquid damp proof membrane.

As these diagrams show, rising damp can be caused by all sorts of defects around a typical house. These ones shown are the most common causes which we see while conducting specialist damp surveys but by no means are they all of the reasons. Other defects which can lead to rising damp style symptoms in buildings can include leaks from pipework, cracks in render anywhere on the wall, cement render on a building more suited to lime render, cement pointing on a solid wall, guttering leaks and the list goes on.

It is worth remembering that gravity affects everything on our planet and dampness is no exception. Water penetrating through cracked render 3m up a wall may only show at the base of a wall giving the impression of rising damp. 

In many cases of suspected or mis-diagnosed rising damp a damp proof course injection plus replastering with a waterproof cement render will not solve the issue and can actually make the situation worse by trapping the moisture in the wall. This trapped moisture can lead to rotten timber floors from dry rot or wood boring insects.

If you are unsure of the cause of rising damp within your property then please feel free to contact us or call 01803 262064. 

Table of Contents

Contact Us

If you need a solution to a damp problem or require a specialist survey then get in touch using this form. We are very friendly and happy to help. 

download how to diagnose your damp free guide

Click the button below

for instant download of your free guide