Cavity Walls In New Buildings In South Africa

SANS 10400-XA (Energy Usage in Buildings)

The 2021 SANS 10400-XA revision requires the construction of cavity walls in place of 230 mm solid brick external walls. This energy-saving change is applicable in all the energy zones in South Africa except in zones 3, 5 and 5H.

How wise this course of action is considering the lack of skills in the building trade will have to be seen!

What is a cavity wall?

A cavity wall consists of two skins separated by a hollow space (cavity). The advantage is that a cavity wall gives better thermal insulation than a solid wall. The space between the two leaves of cavity walls reduces heat transmission into the building from outside.

The following are the advantages of cavity walls when compared to solid walls.

  • This type of wall gives better thermal insulation than solid walls.
  • The hollow space between leaves prevents moisture penetration through the wall from the outside. This prevents dampness internally.
  • They also act as good sound insulators.
  • These walls also prevent efflorescence from occurring.

Construction of cavity walls

how to build a cavity wall using DPC and brickforce
window built in on a cavity wall with vertical DPC

The construction of these walls is technically more difficult than for solid 230 mm walls.

  • The cavity between the two masonry leaves should be a minimum of 50 mm. The gap must be consistent from the bottom of the wall to the top.
  • Below the DPC level, the bricklayer must fill up the wall cavity with concrete or mortar before installing the DPC.
  • The bricklayer then installs the DPC at slab level to step down from the slab-level interior wall across the cavity to the outer wall and weep holes. Its purpose is to drain away any water in the cavity towards the weep holes to discharge it outside.
  • Weep holes must be provided in the external leaf above the Damp Proof Course (DPC) at every 4th brick horizontally.
  • The bricklayer must build in wall ties at every 5th course of brickwork vertically and space them horizontally at every second brick to tie the two leaves of brickwork together.
  • Mortar dropping down in the cavity can stop water from draining away. The bricklayer should leave some bricks out temporarily at the DPC level to clear mortar droppings at the end of each day’s work.
  • The normal method of preventing mortar droppings from falling to the base of the cavity is to use a cloth-rapped batten (38 x 38 mm) or specially sized 50 x 38 mm planed to 45 mm. The bricklayer places the batten on the wall ties while building the wall. The bricklayer raises the batten, using wire tied to its ends and then positions it on the next row of ties.
  • Furthermore, the bricklayer should install a vertical DPC on the sides of doors and windows when closing off the cavity wall. This is to prevent water from driving to the inner face.
  • In addition, the bricklayer should install a layer of DPC and weep holes in the cavity above exposed doors and windows similar to the DPC at floor level. This is to prevent moisture from penetrating the inner leaf.
  • At the roof line, the bricklayer should fill or brick up the cavity for two or three courses below the roofline to stiffen and distribute the load over both leaves. He should also build in roof ties at this level to tie down the roof trusses or beams.
  • No wide brick force can be used to span both leaves and cavities of brickwork. A 90 mm width of brickforce will need to be used on every 5th layer of brickwork on both leaves up to window or door height and every course above that until the cavity is closed at roof height.

My Concerns with the new requirements

The Western Cape Province has already been following this practice for many years. Cavity walls are also better for damp prevention than solid walls. The introduction of cavity walls nationally is to satisfy regulatory requirements for building energy efficiency.

However, such sweeping changes to the construction of brick buildings in other areas of the country may have serious consequences because of skills shortages. They may lead or may have led to substandard work because of the lack of sufficient skills and training of bricklayers and their supervisors!

The newer generation of bricklayers and builders never adhered fully to the requirements of the building regulations before with the construction of solid 230 mm walls! Most of them have had no experience with building cavity walls either!

I have listed some of the issues I have seen on building sites below:

  • In my experience, the bricklayers in the building trade never used collar jointing of the solid brick walls leading to weakened wall structures.
  • The bricklayers seldom place the DPC on a half layer of mortar on the brickwork. Instead, they place the DPC directly on the brickwork. This often led to moisture intrusion in the structure at the DPC level.
  • Generally, no bricklayer has installed DPC on the sides or above the door and window openings to prevent moisture intrusion through the wall at the windows and doors inland from the coastal areas.
  • Few bricklayers build in the correct number of layers of brickforce reinforcing above windows and doors.
  • Often, the bricklayers tooth the brickwork of the internal walls to external walls and corners instead of stepping back the brickwork as required.
  • The mixing of large amounts of mortar resulting in the retempering (adding additional water) of mortar is a common practice. This causes weakened mortar and brickwork.

Most of the issues result from a lack of knowledge and training. This includes not only the bricklayers but also the supervisors!

So how do we get the bricklayers to build the more technical cavity walls correctly?

  • One way is to train the supervisors who in turn can train the bricklayers!
  • Various brick associations and training schools offer bricklaying training. The various training associations and schools may be open to do on-site training.
  • Both the supervisors and the bricklayers can learn from videos that show how to build cavity walls. They all have cellphones on which they can view the videos.
  • Articles by the Clay Brick Association can update supervisors and bricklayers with the technicalities of building a cavity wall.

Let us hope the above happens so that new homeowners will have properly constructed homes!

Conclusion

With the correct training, newly built cavity walls will provide the thermal benefit required by the new revision of SANS 10400-XA. In addition, the construction of cavity walls will minimise moisture intrusion into new buildings if constructed properly. They also provide sound insulation benefits.

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THE HOME DETECTIVE » Home renovation

Building Work, Building Plans and Building Lines

Questions about Building Work, Building Plans and Building Lines

approved plans and house building work

Hardly a day goes by without questions from disgruntled homeowners relating to issues with discrepancies in house plans and building work. When I’m inspecting, I often find discrepancies between the approved plans and the built structure.

If you are selling your house, and don’t have municipal-approved plans or necessary permissions, you could be in trouble. If you are buying a house, and don’t ask for approved plans or permissions, you might have very expensive problems.

Homeowners can also be in trouble with the municipality for the erection of illegal structures. Some municipalities have aerial photographs of suburbs taken every four years to check if alterations have been made to homes. In addition to this, municipalities assign building inspectors to monitor developments on the ground.

The law requires all major building work to have plans drawn up and approved by the local authority. Therefore, it stands to reason that every house should have plans. But this is not always the case! A lack of approved building plans is a major problem for many people buying and selling houses and other buildings.

Sometimes people only discover that there are no plans years after they have bought a property. This comes to light either because they eventually want to do alterations, or because they want to sell. Buyers often find that a house they are buying does not have plans. They then want to know whose responsibility it is to have plans drawn up retrospectively (“as-built”).

It can become a complex legal matter if alterations and additions have been carried out without local authority approval.

Are Building Plans and Building Approval Always Required for Houses?

The National Building Regulations and Building Standards Act specify the need for building plans and approval. Therefore, it is the local authority that governs what can be done in terms of its zoning regulations and National Building Regulations. So it is they who give approval (or deny it) for all building work and renovations on all properties. However, most municipalities are more lenient when it comes to minor building work.

The Act states that the municipality may grant relaxation where the approval of plans requires the necessity of relaxation. However, you will have to apply for relaxation in writing and receive approval in writing.

If your property is within an estate townhouse or cluster complex, you will also need to get a copy of the Estate Guidelines from the Aesthetics Committee, Body Corporate, Residents Associations etc. Moreover, there may be a list of requirements that ensure aesthetic harmony and good building practices within the estate or complex. Furthermore, you will need your plans stamped and a letter from the Body Corporate for Council indicating that they are happy with your planned building.

How the Issue of “Voetstoots” Affects Building Approval and Plans

The purchase agreement made between buyers and sellers of the property will include a voetstoots clause. Essentially this clause indicates that the purchaser accepts the risk relating to defects existing at the time of the sale, patent or latent (but not visible). However, the exceptions to this clause are instances where the seller deliberately and fraudulently conceals latent defects from the purchaser, that they were aware of at the time. In this instance, the seller will remain liable for these defects. But of course, the purchaser will have to provide evidence that the seller knew what was wrong.

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Your Bedroom Paint Colour Can Affect Your Sleep

How Your Bedroom Paint Colour is Affecting Your Sleep

paint colour
Written and contributed by Krista Harper, a freelance writer from California, who writes about home and interior design

40% of Americans get only six or fewer hours of sleep per night. Perhaps you don’t either and have tried everything to make the sandman visit with little luck. Could the paint colour of your bedroom walls be to blame?

It sounds like something too simple to actually work, but the truth is the psychology behind colours has been researched for years. Different colours have the ability to make us feel particular emotions; if you’ve ever felt a difference in your mood while wearing your favourite hue, you know this is true. It’s the reason why a dentist’s office or spa may choose a soothing wall colour while a gym may go for vibrant tones to help its clients feel energized.

Here’s a general guide to the best and worst colours for your bedroom.

First, the Worst Paint Colour

When it comes to getting some shuteye, these are the general paint shades you may want to avoid.

Red

It’s the colour of romance and heat, so you may think it’s a suitable choice for your bedroom to help spice things up. But as it turns it, red is way too energetic. Red light makes cattle more aroused than blue or green light, and red is a common colour in bullfighting as it is believed to excite the bull.

Another study found that when people saw red their reactions became faster and more forceful. Red has also been found to increase the heart rate. Save the colour for roses and date night, but don’t paint your bedroom walls with it.

Bright Colors

Bright colours in general, no matter which ones they are, will stimulate and begin to energize you which is the opposite of what you need when trying to fall asleep. Vibrant shades of yellow, orange and blue are great for other parts of the house such as the kitchen and family room but may make it difficult to fall asleep when used in the bedroom.

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Damp In Freestanding Walls

Do Your Boundary Walls Look Like This?

damp in boundary and garden walls

This photo I took during a client’s comprehensive buyers inspection had rising damp, falling damp and penetrating damp in the boundary and garden walls. In addition, the white marks on the wall were caused by efflorescence.

Often the maintenance of the walls that are attached to or which do not form part of our houses is neglected. These are our boundary, garden and courtyard walls.

These walls are very important in that they protect our privacy and security and are our first line of defence against intruders. Unfortunately, we sometimes do not make enough effort to protect them!

The greatest enemy of these walls is damp which penetrates into the wall from below, above and from the sides of the walls.

Rising Damp

Rising damp occurs as a result of capillary action at and below ground level into porous building materials. These materials are mainly concrete, bricks and mortar. The moisture rises up the wall in this way. It usually occurs where there is no damp proof course (DPC). Freestanding walls such as boundary and garden walls do not normally have DPC built into the walls because it would make the wall unstable. A layer of DPC would break the bond between the wall and its foundation.

The height to which the moisture will rise is determined by the evaporation rate and the nature of the wall. However, the normal limit for rising damp is generally about one metre above ground level.

Rising damp may show as a stain on the plastered and painted wall, the blistering of paint and loss of plaster. A damp area may be evident at the base of walls and in extreme situations, may cause the structure of the wall to wear away and crumble.

Falling Damp

Falling damp is caused by downward water penetration from the top of porous masonry walls. This is as a result of the top of a boundary wall not being adequately waterproofed, if at all.

Walls should be:

  • properly sealed at vertical expansion joints;
  • repaired at copings that have cracked or deteriorating mortar joints;
  • cleaned to prevent the build-up of dirt and moss on upper surfaces of stone or brickwork.
  • Leaves, bird manure, moss and dirt on top of the walls contain weak acids and salts which can promote decay of the masonry and paint if absorbed.

Penetrating Damp

Penetrating damp is a common form of damp. It occurs as a result of the horizontal ingress of water through gaps, cracks and joints in the wall’s structure. Penetrating or horizontal damp can be due to your or your neighbour’s irrigation system spraying against the boundary wall. Moreover, foliage growing against the wall (bushes and trees)can also be the cause. Other causes are deteriorating paint finishes and inadequately ruled joints which allows moisture intrusion into faced brick or stone walls.

Penetrating damp tends to produce localised patches of dampness and decay, whereas rising damp may affect the base of the wall.

Efflorescence

Efflorescence occurs when an appreciable quantity of soluble salts and moisture is present in the masonry. It routinely occurs in masonry construction, particularly in brick and concrete. It typically occurs during the initial curing of the cementitious product. Moisture carries these salts to the face of the masonry or concrete where the moisture evaporates.

As the water evaporates, it leaves the salts behind as a white fluffy deposit. Therefore, to remove it, brush the deposit off when the wall is dry. It usually disappears with time after rains or washing with water.

Efflorescence is generally an aesthetic concern and not a structural one. However, where there is excessive efflorescence, the crystallizing salts within the pores of the masonry can disrupt even the strongest material. As a result, this can lead to the breaking up and crumbling of the structure.

How to prevent damp damage in your freestanding walls

Rising Damp

Rising damp is not easy to resolve in any freestanding, boundary or garden walls because of the lack of DPC.  However, you can do the following:

  1. Make sure that there is no pooling of water against the wall. Good drainage away from the walls is essential. If you have a low point in your garden against your boundary walls you will need to create a hole in the wall at the lowest point for the stormwater to drain away. Your neighbours have to accept a certain amount of your stormwater by law.
  2. Try not to overwater your gardens against boundary and garden walls. overwatering will result in sodden earth around the walls and, as a result, rising damp in the wall.
  3. Keep leaves and other debris on the ground which may retain water away from the walls.

Falling Damp

  1. You should waterproof the tops of all freestanding walls with a layer of an acrylic waterproofing system or any other system to prevent moisture intrusion into the top of your boundary and yard walls.
  2. If there is a concrete or brick coping on top of the wall you must ensure that the joints form a water-resistant seal. You should seal all deteriorated joints or porous joints between the bricks and copings.
  3. Seal the top of expansion joints to prevent water from entering the joint with a silicone sealer.

Penetrating Damp

  1. Check the paint finish regularly on your boundary and garden walls. It may be time to repaint if the finish is chalky.
  2. If you have a sprinkler system make sure that you are not watering your boundary walls. Sprinkler heads are normally adjustable. If yours are not, change them.
  3. Trim bushes and shrubs so that there is a gap between the foliage, branches and the walls.
  4. If it appears that the moisture is from your neighbours’ sides, you will need to talk to them about the problem.
  5. Clean out and seal vertical expansion joints with a good silicone sealer. Any cracks should be sealed as well. Furthermore, if your plastered walls are covered in crazing cracking wash the wall down. Thereafter, when the wall is dry, seal the wall with a sealer and repaint the wall.

Efflorescence is a sign of damp

Efflorescence is caused by moisture absorbed in the wall evaporating and leaving behind salts as a white powder. Therefore, if you repair and maintain your walls as suggested above, very little efflorescence should appear on your walls.

I am not specifically promoting Prominent Paints as all the well-known paint manufacturers produce the same required paints and sealers. You can use most of them to repair and maintain your freestanding walls.

However, Prominent’s video provides very good advice on how to repair moisture damage to boundary and garden walls!

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THE HOME DETECTIVE » Home renovation

Stormwater

Homes without Gutters 

stormwater

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If you are like many homeowners, you have probably wondered why some houses have no gutters to protect against stormwater. You may have wished your own home had none because of the cleaning and maintenance issues.

Gutters are not required by law on a sloping roof. Many modern homes have none, even in instances where they would benefit from having them. There are alternatives that architects sometimes prefer such as concrete paving around the perimeter of your house.

To decide for yourself whether rainwater gutters are necessary for your home, it is best to first learn what the building regulations require.

The Building Regulations do not require roof gutters and downpipes if another suitable means of drainage has been provided to remove or disperse rainwater from the roof away from your home.

However, the Building Regulations do require that any stormwater that flows from your roof or any area that is near your home must not cause damage to the interior of the building, its structure or its structural elements. The regulations require steps to be taken to ensure that stormwater does not accumulate in a way that“unduly inconveniences” you as the occupant of your home.

Furthermore, the system used must:

  1. not undercut the foundations by erosion or flooding
  2. drain stormwater away from your home
  3. not allow stormwater to accumulate against or close to the external walls
  4. make provision for the drainage of any areas on the property where water pools
  5. be capable of being easily maintained and cleaned
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