Remain up to date with the latest standards!...

The incorrect use of DPC as cavity wall trays are expected to cause major problems associated as they don’t comply with standards.

In a booming housing sector and ever-changing landscape, it is vital for businesses involved in construction, notably housing developments, to remain up to speed with the latest changes in the industry and legislation. It can be difficult to keep up with the ongoing changes throughout the industry and changes towards damp-proof courses (DPC) isn’t any different. They are an integral part of any construction project with potential impacts felt not just on strength and structural integrity, but also on the health of all living within. 

As a business owner, house builder, director, or site manager it's hugely important to be aware of relevant new regulations regarding DPC - not just for current works being undertaken but in preparation for future jobs too. In this blog, we will highlight the changes in the legislation and make you aware of the best use for DPC materials. It will also make you aware of the incorrect use of DPC as cavity trays, and which ones you should be choosing for your builds. 

What is DPC?

Damp proof course (DPC) is a physical barrier that prevents water from moving up a wall. The process of water travelling up through the walls is known as ‘Rising damp’. You can either use liquid or physical DPCs to prevent this from happening however, many homes will/should already have some form of DPC. 

The plastic DPCs are installed into the wall in the construction phase, the plastic then acts as a barrier to prevent water from passing through it. They are manufactured in a way to provide a robust damp proof barrier to prevent water from rising up the wall.

DPCs can be installed in brick, stone, and concrete walls, and can be installed vertically or horizontally. An interesting fact is that they originally emerged in the Victorian age and are found in homes built from 1900. 

What types of DPC are there?

Damp-proof courses should adequately resist moisture from reaching the inside of the building. Issues to be considered aren’t just the positioning of DPCs, but also the DPC materials. 

The following materials are acceptable for use as DPCs:

• Bitumen to BS EN 14967

• Polyethylene to BS 6515 (except in cavity trays in walls, below copings, in parapets and as cavity trays) 

• Proprietary materials assessed in accordance with Technical Requirement R3

• Plastic and rubber to BE EN 14909

Please be aware that Some warranty providers will NOT accept polyethylene DPCs for cavity tray applications. These have been used incorrectly as cavity trays in some buildings should NOT be made of Polyethylene for instance. However, from the table below, it is worth noting that Zedex CPT High Performance DPCs can be used in all typical applications. 

There are many types of DPCs to choose from, depending on the wall’s material and the building’s age. FixFirm has a range of DPC products on offer, including:

·        Visqueen Zedex Housing Grade DPCs (range of sizes available) 

·        Cavity Wall Weep Vents

·        Multi-Cavity Closers

·        Visqueen Double-Sided Vapour Barrier Joining/Sealing Tape 

Alternatively, you can CLICK HERE to view the entire range. 

What changes are there in legislation?

There are several changes in legislation from the UK GOV surrounding DPCs that contractors should be aware of.

DPCs are now required to construct new buildings, preventing rising/penetrating damp which can lead to costly repairs due to mould and damp in the building materials. 

Approved Document C requires that to prevent rising damp, a damp-proof course should be:

·        Continuous with any damp-proof membrane on the floor.

·        At least 150mm above the level of the adjoining ground or paving level if it’s an external wall.

·        If inside an external cavity wall, the cavity should extend at least 225mm below DPC, or a cavity tray should be provided, with weep holes evenly spaced every 900mm so that water running down the cavity cannot pass into the inner leaf of the wall.

·        Of the correct width and fully bedded.

·        Either welded or lapped by 100mm minimum.

·        Impermeable to water.

DPCs may also be required:

·        In masonry walls.

·        In joints between wall, door, and window frames.

·        In suspended timber and materials that can carry moisture from the ground.

·        In older buildings that have or have had mould/damp issues.

FixFirm supply DPC materials and our team remain on hand to offer expert advice and support in ensuring the correct use of DPC depending on the application. 

Click here to contact us, or to find out more on DPC related products, visit here: https://www.fixfirm.com/category/building-products-ironmongery-brickwork-ancillaries