The nature of the job determines the total time it will take to install a damp proof course. For instance, whereas a smaller job may require around 1-2 days to complete a bigger job may need up to a week.
On average, a full damp proof course on 3-bed semi should take around 3-4 days.
DAMP PROOFING DEFINITION
It is the process of making floors and walls impervious to water molecules, rising from the ground. Damp proofing is known to protect a building from both timber and structural decay. It is a long-term solution to keeping the interior part of a building free from water.
Usually, after a building is constructed, moisture eventually climbs up the walls through capillarity and then enters the interior part of a building. You may then notice damp spots on your walls & floors, peeling off paint, white powder like staff or brownish staining your walls. These are all indicators of a missing or ineffective damp proof course. It is especially common in buildings with basements.
If you are familiar with such signs and would like expert advice on how to go about it, feel free to get in touch with us.
DAMP PROOFING METHODS
What types of Barriers are used?
There are various types of barriers used to damp proof floors and walls such as damp proof course, damp proof membrane, integral damp proofing, cavity construction, pressure grouting and surface coating.
The two most common methods are:
a. Damp Proof Membrane(DPM)
Over the years dump proof membranes have taken to many forms including the use of asphalt, bituminous coatings, cementitious coatings, resin coatings sheet membranes and cavity membranes.
b. Damp Proof Course(DPC)
Use of damp proof course is considered an alternative to DPM. It includes the use of water repellants, osmotic and pore blocking. These methods were improvised so as to waterproof already constructed buildings since it proved almost impossible to insert them with a physical DPM.
How are these installed?
Water Repellant
A chemical solvent that is in the form of a gel, liquid, paste or cream is used. It is injected into walls via drilled holes and eventually joins up to form an impermeable layer.
Osmotic
It is believed that water molecules rise up from the earth through matter by capillarity or osmosis. As they move electrical potential is developed between the matter and the earth.
The osmotic damp proof course was developed as a result of this theory. In this method, a titanium wire is run around the walls that need waterproofing.
*Initially, a copper wire was used but was soon replaced by titanium due to its highly corrosive properties.
The wire is then connected to the mains which supply it with electricity. Its earth rods short-circuits the electrical potential caused by water molecules rising up a wall stopping any further movement.
Pore Blocking
Cement is combined with water using a ratio of 1:3 to form a semi-liquid mixture which is then injected into a wall’s mortar using a reusable gun. With time, it chemically reacts to compounds that take up the pore spaces. This blocks moisture from rising up the wall.
DAMP PROOFING INJECTION
Damp proofing injection is a cost-effective and proven way to tackle rising damp in a building. Damp proof injection is applicable in all types of masonry walls. A chemical cream solvent is injected into the walls and floors and deeply penetrates the mortar creating a waterproof membrane.
Preparing to Inject Damp Proofing Cream
First and foremost, acquire and wear protective gear. A pair of gloves, gas mask and safety goggles will do.
Preparing to inject damp proofing cream involves:
Step 1 – Consultation
It is advisable to consult a professional to help determine how far moisture content has gone up the wall. This will establish the levels in which it is appropriate to remove plaster.
Step 2- Removing Plaster and Skirting Boards
Plaster and skirting boards are removed to recommended heights. If a qualified person is not available, it is considered safe to get rid of the plaster to a height of 1.5m since water normally rises up to a height of 1.2m.
Step 3- Drilling Holes
Drill holes into the mortar joint (avoid the brick and stones) using a 12mm diameter drill no less than 100mm apart. The holes should be drilled 10-20mm in depth in a continuous line.
Step 4 – Injecting With Chemical
Inject a dry zone injection fluid into the holes under low pressure using a hand pump or gun. Leave it to settle. Given time, the cream will chemically react to form a fundamental layer that prevents water molecules from penetrating the wall.
Note: Injecting with the chemical is considered most effective for newly constructed walls. Additionally, It is advisable to ensure only quality dry zone injection fluid is used for great results.
WHAT IS PENETRATING DAMP?
Penetrating damp is often referred to as rain penetration. It is the infiltration of moisture into the external wall of a building which later manifests itself as a stain of dampness enlarging in proportion after a heavy downpour. This is usually common in older buildings. A cavity wall that is constructed as per the required standards should channel infiltrating water back outside.
Symptoms of Penetrating Damp
For External walls
Brickworks is damaged- This often occurs when water which has penetrated a brickwork freezes causing cracking in the brick that later becomes a weak point in the wall structure.
The growth of moss on the exterior side of the wall- The perfect breading environment for moss and algae is a moist place. A damp wall hence creates a perfect living space for moss encouraging its broad spread on walls. This creates an unattractive appearance to the walls.
The stain of dampness on walls- Stains of dampness on external walls form and their sizes increase when more moisture penetrates into the wall.
For Internal Walls
Plaster damage- Paint and plaster peeling off and discolouration on the wall’s surface is as a result of dampness on the inner side of the wall.
Wooden fixture rotting- Wood rot is basically decay of wooden fixture by a fungus which digests moist wood. Excessive presence of moist in wood causes rot and decay in timber.
The growth of mould on walls- Moisture constantly present on an exterior wall may cause rapid growth of mould and its spread along the wall.
Causes of Penetrating Damp
Faulty building material
Penetration of rainwater may be caused by faulty building material. These are unmaintained gutters with clogged up downpipes and a poorly designed drainage that leaves water stagnant on one part of the floor or roof.
Ageing of building material.
All building materials have a definite lifespan. Weather conditions may affect the building materials and accelerate the rate of ageing. For instance, when water penetrates in a brick and is frozen, cracks are formed enabling water to infiltrate through the cracks created.
DAMP PROOFING EXTERNAL BRICKWORK
The first step is to establish the main cause and fix it. Check all possible leading causes e.g. Gutter, downpipes etc. confirm that all downpipes are in good order and unclogged to allow a smooth flow of water.
Using water seals on the external wall is preferable as this will prevent penetration of water which may cause damping.
Waterproofing your Exterior Brick Walls
External walls are constantly exposed to water sources including rainwater and snow hence a need to waterproof them.
The following are steps to waterproofing exterior walls
- Identify faults on walls and other building materials- Check to eliminate all other causes of structural dampness on the wall. Fix the issue and as a precautionary measure waterproof it.
- Choose the most preferable waterproof material. These waterproof products include: Concrete waterproofing, Silicate-based concrete sealer and Waterproofing paint.
- Prepare the wall to apply a waterproofing-Apply good-quality fillers to repair cracks on the wall to create an even surface so as to ensure good glueing between the substrate and waterproof material.
- Apply waterproof material- Either roller or a brush is used to apply. After applying the waterproof ensure that it fully dries before any interference.
- Assess the product effectiveness- Carry out an assessment to identify if the product meets the required expectations.
DAMP PROOFING FOR INTERNAL WALLS
Condensation
Moist air coming into contact with a colder surface like a wall, window, the mirror is known as condensation. Condensation occurs mostly in corners of rooms and behind furniture. Avoid this by good ventilation of a room.
Penetrating Damp
moisture coming into the house through leaking or cracked pipework, a damaged roof, blocked guttering is penetrated damp. The types of material may influence the likelihood to endure from water entering.
Rising damp
Rising damp is a type of damp that affects the wall of a building. Rising damp occurs when moisture from the ground is absorbed through small tubes and travels horizontally through the wall and if not corrected creates the right conditions for moss and mould growth on walls and peeling of paint.
During construction of a building, a damp proof course is installed at the lower levels of the wall which prevents water absorption. However, the damp proof course effectiveness decreases as the building gets older.
What are the Internal Damp Proofing Options?
Damp proof membranes
It is an impermeable layer polyethene of greater density that is subdivided and attached under the slab and wall to avoid dampness in the inner part of the building. Comes in different sizes with a thickness of between 0.5-1mm.
Damp proof paint
It’s a type of harmless product that minimises the risk of dampness in walls commonly referred to as water-resistant paint. The paint contains a highly powerful polymer that prevents water through the masonry wall hence protecting the wall from damping. The paint mostly is applied to the painted area of the walls and beneath the tile area acting as a secondary protection for wet areas such as kitchen and bathroom.
Cementitious tanking
It is a traditional way of waterproofing. Commonly used in underground wall, cementitious is a microporous cement base coating assisting in restraining water from passing through the wall by enhancing the cement bond.
Liquid epoxy damp proof membranes
Base and hardener are the two components in a liquid epoxy damp proof membrane. It normally used above the ground damp proof membrane on concrete floor and screeds
Anti-mould paint
The reappearance of mould on the wall can be prevented by use of an anti-mould paint. Durable and works as a water resistant on walls thus making it ideal for walls and ceiling in buildings.
DAMP PROOFING INJECTION COST
To calculate the total cost you are likely to incur you need to put into consideration the amount of labour involved, manpower needed and taxes. It will also depend on whether a house is terraced, semi-detached or detached. Damp proofing a detached house is more expensive compared to a terraced one.
What do I Need to Install a Damp Proof Course?
You will need
• Protective gear- A pair of hand gloves, safety goggles, and face mask
• A damp proof course specialist
• Equipment and tools such as chisels, hand drills and a low pressure injecting gun.
• Quick Cure DPC Cream
• Skeleton gun (400cc or 1000cc)
• Electric hammer drill with 12mm masonry drill bit
• Re-plastering additives/materials
• Wall plugs
How much Does a Damp Proof Course Cost?
To determine how much a damp proof will cost you should consider the total size of the building and how thick its wall measure. If it is an uphill task to come up with this data, you can always hire a professional to help you out.
Here is a guide for how much DPC chemical you will require to damp proof a wall:
- 4.5” thick single wall: 1 litre for every 9m from one side
- 9” think cavity or double solid: 1 litre for every 4.5m from one or both
- 8” thick filled or solid wall: 1 litre for every 2m from both sides
Damp treatment cartridges (310ml) can be purchased for around £20 each but you may be able to get 5 for under £100.
For larger projects and thicker walls, you can get 600ml cartridges for around £35 each or 3 for under £100.
