building valuations


Damp proof courses defined


If you need help and advice with regard to building surveys, engineers reports, defects reports, valuation reports including things such as cracks, dampness, condensation, foundation problems, etc,. Please free to phone 0800 298 5424 for a friendly chat.


Damp proof courses defined

Definitions of a damp proof courseWe would refer you to, the excellent free online encylopedia. It says:

A damp-proof course (often abbreviated to DPC) is a horizontal barrier in a wall designed to prevent moisture rising through the structure by capillary action - a phenomenon known as rising damp .

Interestingly, they say:

This technique has been used since ancient times. The Romans used a horizontal course of slate inserted in a wall to act as an impervious barrier.

Building standards in many countries require most new buildings to incorporate a DPC at the time of construction. This may consist of a thin strip of plastic, a course of engineering brick or slate, or a layer of bitumen.

It would be interesting to know what the person who put the Wikipedia definition up does for a living?


Wikipedia definition under damp proof course for properties without a damp proof or a failed damp proof course

Where a DPC is absent or inadequate, there are various means of retrospectively fitting one. A common method in masonry walls is to drill holes into the wall at regular intervals and inject a penetrating chemical (e.g. silicone) into the holes. The chemical is absorbed into the masonry where it dries to form a waterproof barrier. Some irregular stone walls cannot be drilled for a chemical DPC, so an osmotic electrical system is often fitted.

Alternatively the cement joints can be drilled and the chemical injected there instead, although this is a less satisfactory method. A larger volume of chemical will be needed.

Some forms of the chemical are odour free, some have a strong odour, this should be taken into account when purchasing.

We would reiterate this is a definition from Wikipedia and isn't one that we agree with.


The construction definition from Wikipedia


This is interesting too.

What is a damp proof course?The DPC known as Damp Proof Course is usually a thick plastic strip bedded into the mortar between two courses of bricks or blocks. It can often be seen as a thin plastic line in the mortar near ground level.

A DPM is usually a thick polythene sheet laid under the floor slab, to allow the slab dry out and keep out groundwater. It is often laid on a bed of sand, to prevent the sharp edges of the hardcore damaging it.

To create a continuous barrier, pieces of DPC or DPM are welded together. In addition, the DPC is welded to the DPM around the outside edges of the ground floor, completely sealing the inside of the building from the damp ground under it.

In a cavity wall, there is usually a DPC in both the outer and inner wall. In the outer wall it is normally 150-200mm above ground level (the height of 2-3 brick courses). This allows rain to form puddles and splash up off the ground, without saturating the wall above DPC level. The wall below the DPC may become saturated in rainy weather. The DPC in the inner wall is usually below floor level, (under a suspended timber floor structure), or, with a solid concrete floor, it is usually found immediately above the floor slab so that it can be linked to the DPM under the floor slab. This enables installation of skirting boards above floor level without fear of puncturing it. Alternatively, instead of fitting separate inner and outer DPCs, it is common in commercial housebuilding to use a one-piece length of rigid plastic, (albeit an angled section), which fits neatly across the cavity and slots into both walls (a cavity tray). This method requires the need for weep vents to enable rainwater ingress to drain from the cavities otherwise rising dampness could occur from above the DPC.

In old buildings there may be a DPC made from lead . The DPM may be non-existent, leading to damp problems, or it may rely on an impermeable floor finish such as ceramic tiles to keep most of the damp out.

Again, we must stress that definition of a damp proof course comes from Wikipedia and not us.


Different types of damp proof courseDifferent types of damp proof course

There are many different types of damp proof courses, which can be broadly divided into two sections:

Original damp proof courses have been built in as the property was constructed, and

new damp proof courses that have been added after the property was built. They may be into a property that originally had a damp proof course, or with many older properties (prior to the late 1800's), when damp proof courses were first required.


We would refer you to our article on Damp proof courses, why? for more information

Many sources say it was from the Public Health Act 1875, however, Jeff Howell from the Sunday Telegraph and the excellent website , has researched the subject and in his brilliant book The Rising Damp Myth believes the first legislation to be from the local government board's model by-laws of 1877. We are sure in some areas of the country the practice of adding a damp proof course was long established if it was formed as part of a by-law and in other areas of the country it no doubt took some further years these methods were adopted.


Damp proof courses built in as the property was built

House with a plinth to the base of the property built in the 1800s During the course of our surveys on older Victorian and Edwardian properties, where we can see a damp proof course these tend to be the edge of a slate. In many instances we can't actually see any damp proof course at all, as there is a rendered plinth at the base of the property.
White painted rendered plinth to the base of the property, built in the 1800s  


Lead damp proof course

We have read about these being used but we have only seen them used retrospectively and this was to a timber frame property, where the sole plate, which is bottom most timber, meets the brick plinth and makes up the very base of the property. The lead flashing had been added relatively recently and we can see this as being both good and bad, depending upon the detailing. Unless the lead was well formed with a suitable slope it would allow water to sit on a ledge, which would ultimately cause problems.


Modern plastic based damp proof courses

A variety of different styles have been used over the years, such as plyload, which their website informs us is a bitumen free polymeric damp proof course.

It is flexible to low temperatures, resistant to ageing and shrinkage and can withstand superimposed loads.

Interestingly, it comments:

Traditional damp proof courses were made from textiles with bitumen or pitch and suffered from creep under heavy load and therefore have limited life spans.

They then go on to say that these were superseded by high performance rubber products, but these were generally high priced. Alternative cheap polythene products were used in lower specification applications, despite the low strength of the mortar/polythene bond and an example of a modern damp proof course.

Information from the website.

Another manufacturer is Anderson and they do a variety of damp proof courses; from a standard one that is bitumen free and uses a blend of polymers and elastimers, to a high load variety, to a bitumen and polyester based damp proof course that is advertised as being very robust, to a high performance DPC, that is capable of both gas and damp proof course existence.

Funnily enough, whilst we looked for manufacturers of damp proof courses, the Internet offered us far more companies that inserted damp proof courses as a remedial service. We may have been using the wrong term, or the inserting of a damp proof course may simply be bigger business.


New damp proof courses that have been added after the property was built

Damp proof courses that are added at a later date

These fall into four areas:

the insertion of a damp proof course

the repairing of a damp proof course

magic tubes tubes

the electronic barrier system


DIY inserted damp proof coursesDIY inserted damp proof courses

If you look to website, who offer drill and cartridge kits for your house for under £100!

Damp-proofing cream soaks in over an hour and reacts with the water in the masonry to form a complete DPC. BBA Certificate /4202. This is based on a silane/siloxane paraffin emulsion and all you do is:

Drill a whole into the wall, along the line of the mortar joint.

Slot the cartridge into a silicone gun and attach the nozzle, which you will need to buy from them.

Squirt the cream into the hole.

Job done; no more damp.

It says it is suitable for stone, brick masonry rubble on most walls, a full proof DPC every time!

There are many companies offering the insertion of a damp proof course; from large companies, such as Kenwood Plc , RentaKill , Protim and Pass & Co. Timber Preservation: and many other local companies; search on the Internet or in your Yellow Pages to see that there is plenty of choice.


Physically inserted damp proof courses

The physically inserted damp proof course


Although we have never seen it, we have heard it talked about. This is where, literally, a section of the wall is removed and a slate damp proof course is inserted, although we can't see why it can't be any other sort, and the building is gradually worked around (we assume) until the damp proof course is in place.


Magic tube system (the Knapen system)

Often advertise on the front of national newspapers, so we assume they sell a lot of them to make them worthwhile, although we can't say we've seen more than a dozen over 20 odd years.

We found the gist of this explanation in a book called Damp Walls by R W Castle, and on .

This system involves a tube of approximately 2.5cm diameter being inserted into the wall (not an easy task in itself). The frequency of these tubes depends upon the material into which they are being inserted, the ideal being that it increases the evaporation of moisture by ventilating the property better.


This article utilised:

The Rising Damp Myth by Jeff Howell: Bricklayer, Chartered Surveyor and Chartered Building Surveyor

Mike Parrett's information from the SPAB (Society of Protection of Ancient Buildings) website, particularly in relation to annual maintenance work

The article by Tim Hutton MA MSc MRBs on Building Conservation 1998.

Dr Jagjit Singh, the excellent , who provide a do-it-yourself damp proofing kit, Tel. No. 0845 373 0110, local contact Ashley Palmer at Tel. No. 07545 330675.


You may also be interested in these other articles about dampness issues:



Resolving Dampness in your Basement

Dampness in Buildings - Basics Article

Dampness in Buildings - Technical Article

Dampness Defects Report

Dampness Problems

Condensation Problems

Damp Walls

Shared Freehold and Problems with Damp

Damp Proof Courses - What are these for?

Damp Proof Specialists - Talk to us First

How do Older Properties keep dry without a damp proof course?

French Drains

Rising Damp and Independent Reports

Please see our section on:

Specific Defects Reports


If you truly do want an independent expert opinion from a surveyor with regard to structural surveys, building surveys, structural reports, engineers reports, specific defects report, dampness issues, dilapidations, home buyers reports or any other property matters please contact 0800 298 5424 for a surveyor to give you a call back.

If you have a commercial property, be it leasehold or freehold, then you may wish to look at our Dilapidations Website at and for Disputes go to our Disputes Help site .

We hope you found the article of use and if you have any experiences that you feel should be added to this article that would benefit others, or you feel that some of the information that we have put is wrong then please do not hesitate to contact us (we are only human).

The contents of the web site are for general information only and is not intended to be relied upon for specific or general decisions. Appropriate independent professional advice should be paid for before making such a decision.

All rights are reserved the contents of the web site is not to be reproduced or transmitted in any form in whole or part without the express written permission of


If you require any information about Dampness in

Properties please telephone us for help and advice

0800 298 5424



Home Buyers Reports Property Surveys - why we're the best. Engineers Reports
© Copyright
Site Map

1stassociated-logo-for-footer IVSA-badge IVSA-putting-client-first call-us-for-footer

New Survey Software for more information click here Survey Software 1st | Modern Methods of Surveying

We have thousands of free property articles to help you - or call us freephone on 0800 298 5424

We have been working in the property industry for many years and have been
providing free property articles for over ten years. All for free and to help you with buying your next property.

House and Home Surveys and Useful Information

All you need to know about Building Surveys

Building Control, what do they do?

Designers and Architects will they save me money or will they cost me money

Enviroment, Your Building and Garden Gnomes

Estate Agents help sell houses and work for the vendors

Have a Structural Survey to protect you against structural problems

Home improvements, builder problems and ideas for you on how to solve them

How a Surveyor values a property, Chartered Surveyors and Regulated Valuers

How Chartered Engineers and Building Engineers can help you

Listed Buildings and Conservation Areas

NHBC National House Building Council

Structural Surveys and How We Can Help You

Traditional and Non-Traditional Houses and Mortgage Problems

Valuations and how much is the building worth?

Whats the difference between a Chartered Building Surveyor, Chartered Surveyor and an Independent Surveyor

Useful property problem articles by Chartered Surveyors explaining building issues to avoid

External - Helpful information on building problems on the outside of the property

Chimney issues and problems

Cracking and Movement Problems and Surveying Solutions

Flat Roof Problems, how we can solve them

Foundations and Structures and Settlement and Subsidence and Underpinning

Pitched Roofs Problems and Solutions

Roof Problems

Wall Problems

Windows and Doors and Fascias and Soffits and Wet Rot and Dry Rot and other problems

Internal - House problems we have investigated inside

All you ever need to know about floors

Asbestos in your home, what you need to know

Ceiling Cracks and Structural Problems

Condensation, Damp and Black Mould Problems

Cracking and Movement Problems and Surveying Solutions

Windows and Doors and Fascias and Soffits and Wet Rot and Dry Rot and other problems

Woodworm is it a problem or not? Is it active or not?

Services - Building help and advice on costly services

Drainage, what's underground can affect what's above ground

Heating; I just can't get my house warm enough or alternatively I just can't get my house cool enough

You can't mess around with the electric, you need an expert


Commercial Property Services

Building Terms Explained and Directories

Commercial Property Surveys

Commercial Structural Surveys

Leisure Facilites

Offices Large and Small

Shops and Retail

Warehouse and Industrial Buildings

Dilapidations Help and Advice What is a Dilapidations Notice?

A Beginner's Guide to Dilaps

Damp Mould and Condensation

Dampness Rising Damp Mould Black Mould Condensation

Dilapidations and Negotiations

Dilapidations Claim by a Landlord

Energy Saving what can I do?

Finance what is a Financial Adviser (We are not Financial Advisors)

Fire Risk and Help

Health and Safety Risks

Insurance how do I get the correct property insurance?

Landlords Surveying Advice

Property Investment how can I invest in property?

Property TV Reviews by an Independent Surveyor

Schedules of Condition Leasing a Commercial Property

Scotts Schedule and Section 18 Valuation

Tenants Surveying Advice

Weather how does weather affect my property?



Snow and Ice

Strong Winds

Reviews from clients on Commercial Building Surveys

Churches and Charities, helpful reviews from our clients

Industrial Buildings and Warehouses and what our clients say about us

Offices Large and Small, reviews and feedback from our clients

Pubs, Restaurants, Hotels and other Leisure facilities we have surveyed over the years

Shops and Retail, helpful reviews from our clients


First Time Buyers

Buying a Leasehold or Shared Freehold Home

Buying and Selling Houses for the experienced house and home purchaser

First Time Buyers how do I go about buying my first house and home?

Improve your property knowledge with our presentations on house, homes and commercial property

Building Surveys

Building Surveying Useful Information


Dilapidations Presentations in Detail

Final Year Building Surveying Exams for University Students or those that would like to know more

How old is your Building? Which era was it built in?

Party Walls

Surveyors and Design Tools

Disputes and Party Walls

Boundary Disputes

Building and Property Disputes

Party Wall Book Reviews

Party Walls Your Rights and Responsibilities

1stAssociated Surveyors Review for Structural Surveys and Building Surveys

Building Surveys, reviews and feedback from satisfied customers

Buy to let property clients, what they say about our structural surveys

Buying at auction, review of the survey

Buying bungalows and retirement properties and how our surveyors can help

Both at work / busy couples, how we can help and some 1stAssociated client reviews

Families with a young person flying the nest, reviews and feedback

First Time Buyers, what they say about us

Listed buildings, structural surveys

Older buildings, a review of buying an older house

Families with children looking for a new home, feedback and reviews

Buying a Non-Traditional Property

Residential Surveys

House and Home Surveys

Commercial Building Surveys

Commercial Surveys

1st Associated Surveyors Are Also Available in the Following Areas:

East Anglia and East

South and South East

West Country and South West


North and North East



London Markets

London Parks



Areas of Britain

1stAssociated Independent Expert Property Surveyors

Specialists in Home Buyers Reports, Building Surveys and Structural Surveys and Schedules of Condition

All Surveyors are Royal Institution of Chartered Surveyors qualified and RICS regulated

and are Members of the Independent Surveyors and Valuers Association

Putting the Client First

We do not accept service of documents by email or fax