The main objective of this assignment is to look at seven aspects of a given material. This one deals with 4 commonly and uncommonly used waterproofing systems. These are the EPDM system which comprises of rubber sheeting, usually laid on roofs. Bituminous Paint systems which are applied on planters etc. in the building industry. Thirdly a Paint/powder mixture that forms a layer of film that is used in wet areas and finally the traditional D.P.C. or damp-proof course system.
The seven aspects to be looked at for each of these products are:-
‡ Properties of the Material
‡ Performance Standard Required
‡ Compatibility with other Materials
‡ Visual Characteristics
‡ Fire Resistance
‡ Cost Effectiveness
Properties of Materials
Most of the materials that are used to waterproof buildings are made from oil based or synthetic based products or in some cases rubber or metal. It doesn’t matter what the material is, the materials aim is to prevent the water or dampness from penetrating into the insides of the building.
The first waterproofing material is a rubber based product called EPDM (Ethylene Propylene Dientermonomer). It’s uses are on flat roofs of large office block and other commercial or industrial projects and for tanking for underground basements and the like. Firstly due to its rubber composition it has a high tensile strength and can resist great levels of puncture. It has a good resistance to U.V. radiation and is resistant to other weather types such as extreme temperatures (from - 500C to 1000C). Finally it is resistant to rot damage and most common chemicals will not corrode the sheeting.
The second type of waterproofing material is the liquid bituminous type. It’s properties are that it is applied cold requiring less labour. It is non-flammable and therefore cannot catch fire. The only bad aspect of using this method is that it must be coated with another paint to protect it from U.V. radiation if it is exposed to the sun and other atmospheric conditions.
Although most waterproofing occurs on the outside or on the perimeter of the building, the wet areas have to be taken into consideration. This type of product (which is sometimes called dampseal) is a paint powder mixture that is applied onto the floor and walls of the shower recess. This product once applied creates a layer so that dampness and moisture do not penetrate the walls and create problems in adjoining rooms. This material is fire resistant, can cope with U.V. factors, has a long life and is flexible allowing movement in walls and floor joints.
The traditional method of waterproofing the majority of buildings (residential housing) is by using the damp-proof course on the bottom few courses of brickwork. In this method, a metal with galvanized or bituminous coating is placed in the bedjoints of the brickwork. This flashing is there to prevent the dampness from the ground from penetrating up the walls and causing problems internally. This method which is usually good to prevent the problem can sometimes fail if:
After the placing of the D.P.C. mortar droppings or sand which has fallen in the cavity can act as an alternative route for the dampness as it escapes the D.P.C. Another area of waterproofing that must be looked at is the water penetration that occurs from rains that come in through exterior walls. During construction the right mixture of mortar should be used so that the mortar will not break or fret away. Also bricks that show visible stress cracks should not be used as these cracks have other ways which the water could penetrate. If proper materials are used and the labour used to install them is also of a good quality the old method of a damp-proof course should be sufficient to meet requirements.
Performance standards required
If installed in the right way and in accordance to the manufacturers recommendations all of the above waterproofing systems will comply with the requirements set out in Australian Standard - AS 3740-1994.
In addition to this the building code of Australia requires that that wet areas be made impervious in accordance with the above Australian Standard.
The EPDM layer must be installed by a qualified installer who has passed a certificate of waterproofing course.
Compatibility with other materials
Due to the fact that most of these products are chemical based they can be applied to nearly any surface.
Firstly the EPDM rubber sheeting can be applied to :-
‡ Metal gutters and the like.
The main issue when applying is that the above materials be clean, dry and have an even surface. If these are not met then the compatibility issue is irrelevant.
The bituminous paint can be applied to :-
‡ Brickwork and other Masonry
‡ Fibre-cement Sheeting
For the paint to work on masonry, the surface must be clear of and fine cement particles and it should be even.
The wet area waterproofing (dampseal) is also compatible to all above materials except for the metal products. This product due to its properties can also be applied to water resistant plasterboard.
Finally flashing may redirect the water but at the place where it abuts a wall or other material water can seep through causing damage. When flashing is used a sealant such as silicone should be used to seal and watertight the joint in question.
As most waterproofing is there to conceal joints in roofs or tanking the material in question will not be seen. However with the EPDM and similar types the finish on the roof can sometimes be seen by those in higher buildings. EPDM’s finish is one that resembles a flat black foam. With other types of the membrane that are similar to EPDM, other materials such as bonded gravel, drainage slabs, asphalt or synthetic grass - astroturf can be used to conceal or landscape the roof area.
The bituminous paint usually cannot be seen as it is used in planters which are covered up with soil and therefore cannot be seen. It is usually Black in colour and sometimes has small fibres in it. The dampseal is blue in colour and is concealed with ceramic wall and floor tiles so that it will not be seen.
The DPC and flashings are also seldom seen. The first one is concealed in brickwork and is usually a piece of P.G.I. metal or plain metal coated with bitumen.
As waterproofing materials are placed in roofs and other hard to reach areas of a building, it is generally the case that they will stay in place for quite a few years.
With the EPDM and similar products any defects or service repairs that must be carried out will be by the qualified installers or the firm that installed the waterproofing system. This EPDM system is very tough so it would take many years of wear and tear before it would have to be repaired or resurfaced.
The Bituminised paint as well as the wet area paint both do not need servicing. Once these are in place they will stay in place for the life of the building.
The only aspect that has to be serviced on a building is re-pointing the mortar joints as it is here that a large mass of water could enter the building in a storm. When re-pointing detail should be looked at when choosing the type of joint.
Although these products are made from rubber and oil based products you would think that they would suddenly catch alight if a flame or fire arose. The only system that is fully fire resistant is the Damp-proof course as well as the paint system used in wet areas.
The EPDM system and the bituminous paint do not catch alight when a flame hits them, but once the heat intensity goes over 1500C , the material starts to melt and deteriorate until it reduces into waste.
The bituminous paint also does not catch fire but once the immediate temperature reaches 1600C the hardened bitumen softens and will come off if the material is stripped off. When it does reach this temperature the paint will also not run or melt by itself. Some work would need to be done to remove the paint.
The cost is probably the factor which influences builders and clients for which system to use on a given project. All of these systems have high initial costs but in the end little or no maintenance costs are needed.
The EPDM has extremely high costs due to the amount needed to cover a commercial sized buildings roof. As well as this the labour costs are high as specialised tradesmen are needed to install it. All in all it’s cost effectiveness is quite high but the product will need not be repaired for quite a few years.
The bituminous paint is not as expensive as it can be installed by a labourer if need be and it is a simple material therefore not requiring extra corner bits etc. One 20litre can will cost around $A 40 while the indoor type paint/powder system will cost around $A53 per 20 litres.
In conclusion waterproofing materials are usually chemically based and treated against fire, heat to some extent and other elements. There are many other types of waterproofing systems on the market that deal with other aspects of a building but the 3-4 types that were selected are the majority of the systems that are chosen. It doesn’t matter which system is chosen, the main thing is that it meets its primary objective of not to let water or moisture/dampness penetrate into the inside of a given building.
Pabco Waterproofing and
Sealants Catalogue - 1987
Current world practice
in the remedial treatment of Rising Damp -
Douglas A. Kagi, Ph.D.
Structural Waterproofing - John C. Maxwell-Cook, 1967