## Insulation Basics – Brick Veneer Walls

This post will help you understand how much heat you lose through walls. A previous post has explained ‘R’ and ‘U’ values

When considering insulation a typical Australian brick veneer wall would be:

 Element R value Outside surface air layer 0.03 110mm brick 0.08 25mm cavity 0.12 R1.5 Insulation 1.5 Plasterboard 10mm 0.06 Inside surface air layer 0.12 Total R value 1.91 U value = 1/R 0.51

The heat losses or gains for 150 sq m (fairly typical external wall area) of this type of brick veneer wall at 15 degrees above, or below, outside temperature will be:

Area x ‘U’ x temperature difference = watts per hour

150 m2 x 0.51 x 15 degrees = 1178 watts per hour

Heating/Cooling Requirement = 1.17kw/hour

To change the U value calculation simply change the value of the element or add an element in.

Example 1 Changing the Insulation to R 2.0

New Total R = 2.41

New U = 0.41

Reduced Heating/Cooling requirement to 0.92kw/hr

Example 2 Adding a reflective building wrap to example 1 (increases cavity R by 0.18

New Total R = 2.59

New U = 0.39

Reduced Heating/Cooling Requirement to 0.87kw/hr

Remember this isn’t the total heating requirement as heat is also lost through windows, ceilings floors and ventilation.

## Render or Brick?

Rendering popularity comes and goes……………… However I think “Why pay more for a something that is only going to require painting in the future?”

As my old woodworking teacher once told me “There’s nothing wrong with being lazy as long as you are intelligently lazy.

That means getting the job done but saving effort, both now and in the future.”

### Positive

Rendering does have its place:

• It gives a good finish if you are building using Hebel blocks or Foam Panels (See this link: Rendered Foam Walls), which you may prefer to use as they have a better thermal performance than bricks.
• The render, particularly if painted a light colour, will improve the thermal performance of the walls.
• You need to do it for some of the Home Builder techniques such as straw bale housing, or even if your DIY bricklaying is a bit rough.
• Its handy if you are renovating a house and the previous builder has painted the bricks.

### Negative

Apart from the exceptions above here’s why I don’t like render as a final finish:

• Additional cost at time of construction.
• Is it really hiding the use of leftover bricks from previous jobs and perhaps poor workmanship by the builder.
• It can look fairly flat and bland in large areas like the house below:

• Future time cost and effort in repainting.
• If you get building movement it really shows up, with a crack across a flat plain wall. It’s then very hard to satisfactorily repair and hide the crack.
• Render really shows dirt, spiders webs,and water stains.

Bricks are making a comeback as people who have rendered 10 years ago now find that the additional cost was only the start.

Having a house painted every 10-15 years is an expense that basically starts at \$12K. Personally I’d prefer a family holiday .

Render costs around \$20,000 on a 30Sq home, plus painting, plus more for maintenance……Brick veneer requires a wash, at the most, with a low pressure hose.

Some people say the modern Acrylic renders are better than the cement renders but I remain to be convinced.

What do you think?.

## Wall Dimensions Standard Bricks

When you are deciding about building dimensions its better to take into account the size of building materials.

With brick veneer being so popular that means the dimensions of the bricks.

Make sure that all lengths, are based on either all complete bricks, or complete bricks with one half brick.

Similarly all heights should be based on complete bricks. Doing this has the following advantages:

• Less wastage of bricks
• Savings on labour due to less cutting of bricks
• Stronger walls due to more regular bonding

The Work (design) Size of a standard brick is: 76 mm high x 230 mm long x 110 mm wide. These seem unusual dimensions but they are based on the old imperial dimensions of 3 inches by 9 inches by 4 inches.

When calculating overall wall dimensions it is normal to allow for 10mm vertical and horizontal mortar joint between bricks.

I have included  ‘Tables of Dimensions for Brickwork’ at the following two links:

## Checking Bricks Meet Specification

Clay brick sizes may vary after they are fired but size variation between bricks averages out when blended properly during laying by a good bricklayer.

There are three dimensional quality levels for bricks DW1, DW2 and DW0

If you want to check the quality of the bricks the normal method of measuring is to measure 20 bricks dry stacked together against the work size of 20 Bricks.

• Dimensional Category DW1 means the height and width will differ by less than plus or minus 50 mm from 20 times the work size, and the length will differ less than plus or minus 90 mm.
• Dimensional Category DW2 means the height and width will differ by less than plus or minus 40 mm from 20 times the work size, and the length will differ less than plus or minus 60 mm.
• Dimensional Category, DW0 means there are no requirements. This is usually reserved for non-standard shaped bricks and bricks that have been rumbled or otherwise distorted during the manufacturing process for aesthetic reasons.

## Brick Fences

As I travel around the Melbourne Suburbs I see lots of brick fences……….. A problem with a large proportion is that they have obvious cracks.

If you don’t believe me just walk around your neighborhood and look at a few brick fences yourself!

So why are there problems with brick fences?

• The actual cost of the wall in both materials and labour is high resulting in people trying to minimise on wall, and supporting pier dimensions.
• Although many people think of brickwork as an inert material it is still subject to expansion and contraction which needs to be accommodated with proper detailing.
• Brick work is actually a fairly brittle structural material which relies on its weight for a lot of its strength. The jointing material of mortar is much weaker than the bricks.
• Due to the considerable weight of brickwork it needs substantial (costly) foundations which will not be subject to any settlement.
• If it’s built on clay there is more chance of movement……The soil below the narrow foundation can gain, or lose, moisture more readily than under a house slab.
• Although it ‘feels’ as solid as a concrete wall it may only have a tenth of the structural strength of a well designed reinforced concrete wall.

Here are a few recommendations;

• Don’t try to save money on the foundation. After all that’s what all those expensive bricks are standing on. A 500mm wide x 300mm deep concrete with trench mesh should be the minimum.
• Brick piers a minimum of 320mm x 320mm with vertical steel reinforcement.
• Minimum wall thickness should be 210mm (double brick)
• Have articulation/expansion joints at 5m intervals.
• Use horizontal steel reinforcement every 6 courses.
• It you are using the wall to retain soil get the wall properly designed.

All sounds too expensive?,,,,,,,,,,,,,,,Perhaps brick piers with infill timber or steel panels may be the way to go!

Remember – “There is no such thing as a cheap brick wall”.

## Wall Height – Standard Bricks

The table shows the height of walls based on ‘Standard Bricks’ of 230mm x 110mm x 76mm with 10mm mortar joints.

 Bricks Wall Height (mm) Comments 1 86 2 172 3 258 4 344 5 430 6 516 7 602 8 688 9 774 10 860 Good Height For Barby 11 946 12 1,032 13 1,118 14 1,204 15 1,290 16 1,376 17 1,462 18 1,548 19 1,634 20 1,720 21 1,806 22 1,892 23 1,978 24 2,064 25 2,150 Min Height Non-Habitable Room* 26 2,236 27 2,322 28 2,408 Min Height Habitable Room* 29 2,494 30 2,580 31 2,666 32 2,752 Typical Upgrade Room Height 33 2,838 34 2,924 35 3,010

*For More on ‘Habitable Rooms’ check this link: Habitable Room

For wall lengths see this link: Wall Lengths

## Wall Length – Standard Bricks

If you are looking designing at a floor plan it can be useful to think about planning the walls based on brick size.

The table below is based on ‘Standard Bricks’ of 230mm x 110mm x 76mm with 10mm joints.

It provides both the wall lengths, and the opening sizes.

 Bricks Wall Length (mm) Openings Width (mm) 1.5 350 2.0 470 490 2.5 590 3.0 710 730 3.5 830 4.0 950 970 4.5 1,070 5.0 1,190 1,210 5.5 1,310 6.0 1,430 1,450 6.5 1,550 7.0 1,670 1,690 7.5 1,790 8.0 1,910 1,930 8.5 2,030 9.0 2,150 2,170 9.5 2,270 10.0 2,390 2,410 10.5 2,510 11.0 2,630 2,650 11.5 2,750 12.0 2,870 2,890 12.5 2,990 13.0 3,110 3,130 13.5 3,230 14.0 3,350 3,370 14.5 3,470 15.0 3,590 3,610 15.5 3,710 16.0 3,830 3,850 16.5 3,950 17.0 4,070 4,090 17.5 4,190 18.0 4,310 4,330 18.5 4,430 19.0 4,550 4,570 19.5 4,670 20.0 4,790 4,810 20.5 4,910 21.0 5,030 5,050 21.5 5,150 22.0 5,270 5,290 22.5 5,390 23.0 5,510 5,530 23.5 5,630 24.0 5,750 5,770 24.5 5,870 25.0 5,990 6,010

NB. Maximum dimension between Articulation Joints is 6.00 (see this link: Articulation Joints)

For Wall Heights see this link: Wall Height

## Ornamental Brickwork

In Australia most brickwork these days consists of large panels of stretcher bond brickwork.

Where there are openings it usually spanned by steel lintels giving a square opening.

I’ve just shown a few examples of a different approach from my recent trip to England.

I wonder how many current Australian Craftsmen would be able to do something like these examples?

## Why Do Bricks Have Holes?

The holes are called ‘Core Holes’

Before ‘Core Holes’ were a thing most bricks has a large surface indentation called a ‘Frog’

So here are some reasons for the holes.

• Better locking in with the mortar. As the bricklayer taps the brick down the mortar squeezes into the holes improving the hold between the set mortar and the brick.
• Easier to Fire. When the brick is fired in a kiln the holes allow the heat to better penetrate the brick. . . . saves time and fuel.
• Lighter bricks. Easier on the bricklayer, and trucks can carry more saving material costs.
• Less material. More savings as it uses less clay

## Front Fence Failure

Generally you don’t have to go far to find a front brick fence falling over like this one.

Normally they fall over in the direction of the street.

So why is this failure so common?

## Reasons For Failure

1. People think “It’s only a brick fence” so don’t put a good foundation in, and only make it a single brick thick.
2. Simple brick construction is fairly brittle when any stress is placed at 90 degrees to the wall face.
3. Frequently the soil is built up on the garden side of the wall making the wall a retaining structure. with the consequent stresses which can be significant.
4. If the wall is built on reactive clay the street side of the wall is kept dry by the pavement while the garden side gets water seeping through and can be subject to soil heave.

## What You Can Do

• Construct a substantial foundation
• Make the wall at least two bricks thick with steel reinforcement built into the wall.

or

• Consider alternatives like panel fences or hedges

## Patterned Brickwork

What do you think of patterned brickwork?

I think it can look well if its used with restraint and understanding.

Unfortunately I don’t think this example that I recently saw qualifies.

Those triple block features at the window are supposed to represent Quoins (stone blocks to reinforce corners) . . . .that and the over complex single pattern on the building corners are the opposite of what you would see on a genuine old patterned brick house.

A much better option would be to have the ‘Quoins’ on the corners and a plain brick window edge.

Do you agree? . . or do you think I’m just being picky?