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 » Homeowner

Bathroom Mould – How To Get Rid it!

Bathroom Mould

bathroom mould
Don’t let mould take over your bathroom! Prevention is better and less costly than cure!

The source of moisture in bathrooms is mainly the steam from hot baths and showers condensing on the ceiling and walls making bathrooms the ideal breeding ground and bacteria. Mould on bathroom ceilings, walls and tiles is mainly the result of condensation and poor air circulation in the bathroom.

How to get rid of bathroom mould

The first step to cleaning mould from a bathroom ceiling and walls is to use a product that will kill the mould and remove the staining. Therefore, this means using products like Domestos, Jik or any other bleach you may have in your kitchen. However, there are also propriety products like Mould Buster which have been specially developed to get rid of mould. If you prefer to use one of them follow the instructions carefully!

Safety first when cleaning up bathroom mould

Always use PPE (personnel protection equipment) when using dangerous chemicals like bleach and even vinegar!

The PPE listed below is essential to protect yourself against the cleaners:

  • Rubber gloves
  • Eye protection
  • Breathing apparatus (not dust  or medical masks)
  • Coveralls

How to kill the mould

  • If you decide to use bleach, create a mixture of bleach and water, using a spray or sponge to apply it to the mould areas in your bathroom. The bleach removes the mould stains!
  • Wash down the area with water.
  • Apply white vinegar with a spray or sponge to the mould area. Vinegar will kill the mould!
  • Wait about an hour before cleaning the area with water again.
  • Let the area dry thoroughly.
  • Ventilate the bathroom to help remove fumes and to help the drying process. Use a fan or heater to speed up the process if required.

Safety Warning

Never mix any other cleaning ingredients with bleach as it could create a toxic gas. Therefore, wash your mouldy ceiling with bleach first, then apply the white vinegar solution separately.

How to prevent mould from forming in bathrooms

Ventilation is the key to preventing mould from forming:

  • Leave shower and bathroom doors and windows open to provide proper ventilation to the bathroom, particularly after hot showers or baths.
  • Wipe down your walls with white vinegar whenever you see mould starting to appear.
  • Consider installing a ceiling fan and ducting to the outside of the bathroom.

Now that you know how to keep bathroom mould from ceiling areas and walls for good, prevention is the key! Be proactive by wiping down the tiled walls in your bathroom and the floor in your shower with vinegar once a week, especially in showers, and you’ll never have problems with mould again.

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HOME PAGE

Imagine What Can Happen If You Don’t Have A Home Inspection!

home inspection and property inspection
Do not let this happen to you! Be wise! Rather have one of my property inspections like a Comprehensive or Critical Home Inspection in Gauteng or part of the North West province!

Why use THE HOME DETECTIVE for your home inspection?

Firstly, you get the best home inspection and most detailed home inspection report in Gauteng! You not only get a defects report but you also get a property inspection report detailing future maintenance issues! Moreover, my inspection reports include advice for repairs and maintenance which is helpful if you are a DIY enthusiast or handy around the house! 

Secondly, your inspection is performed and the report is produced by a highly qualified and Certified Professional Inspector (CPI) who is a member of the International Association of Certified Home Inspectors (InterNACHI)!

Moreover, I come highly recommended on Google Business!

There is no doubt that without a home inspection and report, you are at risk! This is especially true with the “Voetstoots” clause in the “Offer to Purchase“!

At The Home Detective, I understand just how stressful it can be to buy a new home. A home is not just what it appears to be on the surface. It can consist of more than 500 different components, some of them very complex. This includes the roof, windows, doors, structural concrete, brickwork, framework, and components such as electrical, plumbing, cooking, heating, and air conditioning systems.

When considering a home for purchase, minor cosmetic repairs are usually acceptable. However, you need to make sure that everything beneath the surface is in good shape.

How I can help you

I will help you reduce your stress and uncertainty when you are looking for a new home. I will help you choose the right property. My Comprehensive or Critical Home Inspection will help reduce the risk of buying a house with structural defects, leaks, dampness and other defects.

Furthermore, I work only for you! My home inspection services give you unbiased, objective information about the property. Above all, I am an independent and impartial home inspector.

In addition, a comprehensive or critical home inspection and report is not going to cost you an arm or a leg! Don’t let the home inspection cost put you off! It may cost a bit, but it could end up saving you many thousands in repairs and maintenance!

My inspection services for your peace of mind

You don’t need to attend the inspection if you do not wish to. Your inspection report with marked-up photos of the defects will clearly illustrate the condition of the home to you. However, attending the home inspection will give you more insight into the property. In addition, you will also be able to raise concerns while I am inspecting and have your questions answered.

Your comprehensive home inspection report will include:

  • Defects of the property and suggestions for repairing them
  • The property’s strong points,
  • Regular maintenance is a feature of any property. The report will give you a good idea of the maintenance you may need to do.
  • For ease of understanding the inspection report will include photographs. I am also happy to give telephone support if required!

Why choose The Home Detective?

At The Home Detective, I strive to ensure my home inspection services and reports are not only the best in Gauteng but are the best in the business. I value customer service above everything else.

I use the latest home inspection technology and equipment. Therefore, you can rest assured that you’ll receive a thorough and detailed property inspection service you won’t find elsewhere!

In addition, I inspect properties in Gauteng from the north of Pretoria to Johannesburg South and from Brits in the Northwest Province to Springs in the east.

All my inspections exceed the minimum requirements of InterNACHI’s Standards of Practice and I observe InterNACHI’s Code of Ethics.

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THE HOME DETECTIVE » Homeowner

How to monitor cracks

Worried About Cracks In Your House? Having Sleepless Nights?

crack
Here the foundation on the corner of the domestic bathroom had subsidised! Disguising cracks with paint and Polyfilla won’t work! You need to find the cause first and fix that before you patch walls!
crack
The problem here was with the pooling of water on the paving and the level of the paving being close to or at the floor level of the bathroom. In addition, it appears the bath waste or water supply may be leaking.

How to monitor cracks in your walls and floors!

Often, home buyers and homeowners are worried by cracks in the house and boundary walls, especially plastered walls!

The good news is that, generally, concrete, stone, brick and masonry walls and concrete or screeded floors that have cracks less than 1 mm wide (the thickness of a credit card) are common and usually do not warrant any corrective action. Most of these small tight cracks are caused by normal shrinkage as the moisture in the walls and floors evaporates over time or settlement of the structure which usually occurs within the first few years after construction.

Be warned, however, that changes in condition around the structure may also cause settlement many years later! Examples are planting a new garden or tree or removing a garden or tree that is against or close to the house.

Crack Fillers

Note that all cracks should be sealed with paint, caulk (sealer) or mortar to prevent water from getting into the structure.

Moreover, if a horizontal, vertical, or diagonal masonry crack is filled with hard masonry patching compound, any substantial future movement is likely to show up as a new crack in the patched area or nearby.  Therefore, always use a non-shrinking grout to prevent stressing yourself!

Continued movement

Cracks that continue to move are a reason for concern! Continued movement in cracks should be evaluated as there may be a need for corrective action. Therefore, if you notice a crack has re-cracked or the crack has opened or gotten larger it should be monitored! However, first, make sure there is no shrinkage of the filler product.  All cracks that are 5 mm and greater should be carefully monitored to ensure there is no continued movement.

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Roof Crocodiling or Alligatoring

WHAT IS ROOF CROCODILING AND HOW DOES IT AFFECT YOUR FLAT ROOF?

flat roof crocodiling of waterproofing
Flat roof waterproofing looks like crocodile skin. This is crocodiling!

Waterproofed concrete and composite flat roofs on residential and commercial buildings require more maintenance than sloped roofs. They react differently to sun and moisture than tiled or sheeted roofs and require more frequent maintenance to ensure they function as they should. One common problem with many flat roofs is crocodiling.

What is Crocodiling?

Crocodiling is a crazed cracking pattern on the surface of the waterproofing. It looks like crocodile skin, which is where the name comes from.

Crocodiling is a sign that your waterproofing is ageing. The sun’s UV rays dry out and damage the waterproofed surface, and after five years or more years, the coating may develop small cracks. The older your roof gets before you repair the crocodiling, the more expensive it will get.

Extreme temperature changes, changing from hot sunshine to sudden cloudbursts and rain, and even hot winter days and very cold nighttime temperatures will cause new cracks to appear and will make existing cracks worse. 

Leaves and debris will allow water to pool on the membrane which, together with the elements, will hasten the deterioration of the protective coating and waterproofing itself.

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