The Causes Rising Damp in Buildings

Rising damp is a common structural defect which, left unchecked, can cause severe damage to a building structure. This damage can include the spoilage of plaster and other decorative finishes and rot in wall plates, floorboards, floor joists and skirting boards. In this edition of the Twistfix blog, we will look in more detail at the problem of rising dampness and the common reasons for which it can occur.

Rising damp occurs when porous masonry absorbs water and soluble salts from the ground and, in defiance of gravity, the moisture ascends steadily up the wall; this happens through a process referred to as 'capillarity' or 'capillary action' (capillaries are pores that are inherently present within masonry structures). A combination of surface tension and electrical attraction allows the water to rise. As standard bricks and mortar have a relatively large pore structure, they are especially susceptible to capillary action and thus to rising damp.

The process of capillarity and the rising damp it causes has been well understood for many years and it is for this reason that new structures built today include a damp proof course (DPC), laid along bed joints at wall bases, as standard. Before the Public Health Act was introduced in the UK in 1875, the installation of a damp proof course (DPC) as a physical waterproof barrier was not mandatory when constructing a building.

Before the introduction in the UK of the Public Health Act in 1875, installing a damp proof course (DPC) as a physical waterproof barrier was not mandatory when constructing a building. The understanding of the process of capillarity and the dampness it causes are why new structures built today include a damp-proof course (DPC) laid along bed joints at wall bases as standard

The first DPCs were low-level horizontal barriers in the form of rows of moisture-resistant engineering bricks or overlapping slate layers. In newer buildings, conventional DPCs primarily consist of synthetic plastic strips.

Rising damp is especially common in older buildings where the DPC is absent, has been breached or has become defective. In certain situations, it can also occur in newer constructions. For example, property alterations or raising the ground to a level above the damp-proof course can compromise the effectiveness of a DPC.

Anything that bridges the DPC allows moisture to travel above it and cause rising damp. Bridging can occur in many different ways, such as internal plaster extending directly to solid floors at the base of walls or the presence of debris inside cavity walls. Removing the bridging material is the first step in tackling the problem and alleviating a primary cause of dampness.

Twistfix specialises in the supply of premium-quality damp proofing products designed to prevent and remedy the occurrence of rising damp. Our collection of anti-damp treatment options is comprehensive and includes a selection of damp-proof cream, damp-proof membranes and more.

We will be showcasing our array of solutions for damp proofing walls in upcoming editions of the Twistfix blog throughout the Summer, so make sure you are subscribed to our free, regular newsletter to ensure you don't miss out.