There is an interesting article on the BPN website about RBV from July last year.

While it champions the use of RBV (endorsements from architect Glenn Murcutt and the Your Home Technical Manual), the article suggests some of the reasons the technique hasn't become more popular are:

While designers are becoming more aware of RBV as a more sustainable form of construction, the building trades seem to be behind in terms of both education and skills

Consumers are familiar with, and like the look of face brick

Brick is a low maintenance external cladding material

External brickwork is seen as highly secure and fire-resistant

External cladding is generally more expensive than plasterboard, adding to the overall cost of construction

On the up side, the article notes quite a bit of research into the performance of RBV and it's comparing quite well to other construction methods, especially in the type of climate we experience here in Melbourne.

BCA, AS & RBV

As we are beginning the process of sketching the details of our wall design, one thing that keeps coming up is confusion over whether a RBV wall is required to have a cavity. I can't find any explicit reference to reverse brick veneer construction anywhere in AS 3700 or Part 3 of the BCA.

The BCA states (emphases mine):

3.3.4.2 Width of cavity

In brick veneer and cavity masonry construction, a cavity must be provided between the inner and outer masonry leaves or the masonry leaf and the supporting frame as follows:

(a) Brick veneer - not less than 25 mm width

(b) Masonry - not less than 35 mm nor more than 65 mm width

(c) Except for mullions, the minimum width specified in (a) and (b) is to be maintained between the outer masonry leaf and any services, insulation or sheet bracing located in the cavity

(d) Where mullions are located within a cavity as permitted by (c), a vertical DPC must be placed between the outer masonry leaf and the mullion to prevent moisture penetration

The performance requirements of a waterproofing system proposed as an alternative solution to what is described in Part 3.3.4, refer to (bear with me!) Part 1.0.10 and Part 2.2.2:

P2.2.2 Weatherproofing

A roof and external wall (including openings around windows and doors) must prevent the penetration of water that could cause

(a) unhealthy or dangerous conditions, or loss of amenity for occupants; and

(b) undue dampness or deterioration of building elements

Basically, what I understand from this is that a cavity is required in masonry construction to prevent moisture penetrating through to the interior of the building, allow the moisture that does penetrate to escape and also to provide ventilation to prevent dampness.

Anecdotal evidence on the internets suggests some local councils, architects and engineers are insisting on a cavity, while the article I linked to earlier from yourhome.gov.au states:

No cavity is requited for RBV. The brick skin is laid tight to the wall frame without a cavity, as the external cladding provides the primary moisture barrier.

What do you guys think? Should we include a cavity in our RBV wall or not?

Retrofitting

Here is an interesting article about retrofitting RBV walls to a house in NSW's Northern Beaches.

I hadn't actually considered RBV to be a construction method suited to retrofitting an existing building, but in this house it seems to be a reasonable straight-forward and cost effective solution.

The article describes how:

• the existing building frame can be used, reducing the amount of demolition of the existing building
  
• the existing footings can generally be used (subject to appraisal by a structural engineer)
• cement render finish with a white set plaster top-coat was used on the inside walls, as it is important to maximise the interaction of the thermal mass with the room interior
• the set plaster top-coat looks exactly like the existing plasterboard linings when painted, ensuring that the renovation is not out of character with the original (unlike Harmony 9)

Below is a great detail showing the relationship between the existing stud wall and new brickwork:

Recycled materials

Over the next couple of weeks, we should begin sketching up some details of how we're actually going to build our RBV wall.

With this in mind, I just wanted to write something about the materials we will use in the actual construction.

Given this subject is all about sustainability, it would make little sense to go out and buy all new bricks, cladding, timber and a window. I have a large pile of bricks in the back yard to donate to the cause (the ecobricks website has some interesting data on the environmental benefits of using recycled bricks), but I'd also like to suggest we visit Outlook Market, or somewhere similar, to rummage around for the other materials.

I've grabbed some great things from the Mornington branch in the past, but there are a few other branches that might be more convenient for us.

We should also think about somewhere to perform the final experiment where the water we use can either be recycled (car wash?) or runs directly off to a garden bed or something.

Harmony 9

Mirvac's Harmony 9 prototype is an interesting case study in popularising RBV.

The building employs several techniques (see here and here) to achieve a 9.2 star energy rating, including passive solar design, insulation, water and energy saving measures and recycled materials.

RBV construction locates thermal mass to the interior, helps to stabilise temperatures in the building, therefore reducing the energy consumed by active heating and cooling.



I wonder, though, if people are put off RBV because brick is seen as a material to 'show off' and they think RBV will 'hide' it. Brick is relatively expensive, people think of it as an exterior cladding or structural material and are used to using colour (paint) rather than the natural colour and texture of a material when designing interiors.


When I visited, I was struck by the way Harmony 9 makes a feature of the RBV technique: the brickwork is integrated into the design of the building.

The bricks in the bedroom pictured at right were excess bricks left over from a special brick run, reclaimed and used in woven pattern as a feature wall.

The remainder of the wall is finished in plasterboard.







While the bedroom features reclaimed bricks, the livingroom features a wall of recycled bricks, supplied by ecobricks in Clayton.

I love the way a pattern has been created with the painted and different coloured bricks, rather than just using clean or new looking bricks as in the bedroom.



Perhaps making a feature of the interior brickwork, rather than hiding it behind a layer of paint, render or plasterboard, will encourage people to see the aesthetic design potential of RBV, as well as its role in designing a more sustainable building.

Industry Examples..

While largely ignored by the building industry, reverse brick veneer construction has been acknowledged by several mainstream sources as a good method of construction.
Home Improvment Pages says http://www.homeimprovementpages.com.au/article/Benefits_of_Reverse_Brick_Veneer
while Building Product News says http://bpn.com.au/Article/Behind-the-fa-231-ade-reverse-brick-veneer/519938.aspx
and http://bpn.com.au/Article/A-housing-eco-challenge/525735.aspx

There are construction companies around who specialise in this method of construction, such as http://www.ruralbuilding.com.au/ , while even the mainstream builders have begun to experiment, for example Mirvac and their Harmony 9 http://bpn.com.au/Article/Harmony-9-the-future-of-housing-design/519936.aspx and http://www.mirvacdevelopment.com/waverleypark/harmony-9-

Hopefully this indicates a shift towards reverse brick veneer constuction, although we don't hold out much hope of it taking over from conventional brick veneer....

Cheers,
  Glenn

Regulatory issues...

Reverse brick veneer construction is not explicitly covered in the relevant Australian Standards or BCA, which can cause some regulatory issues if you strike a particularly nasty pen-pusher.

Reverse Brick Veneer walls must comply with BCA Volume 2 Part 3.3 - Masonry, specifically 3.3.1.3 Internal Walls.

BCA Part 3.3.4 says the following regarding masonry walls.
3.3.4.2 Width of cavity
In brick veneer and cavity masonry construction, a cavity must be provided between the inner and outer masonry leaves or the masonry leaf and the supporting frame as follows:

(a) Brick veneer—not less than 25 mm width.

(b) Cavity masonry—not less than 35 mm nor more than 65 mm width.

In the case of reverse brick veneer the cavity is not required, as the masonry component is not exposed to the weather, but some building surveyors or other relevant approvers may insist on a cavity just to stick to the letter of the codes.

As far as Australian Standards go...AS1562 - Design and Installation of Sheet Roof and Wall Cladding can be relevant for the outer skin, while AS3700 - Masonry Structures and AS4774 Masonry in Small Buildings apply to the internal structure. The masonry component of the wall can either be structural, with the external cladding simply attached with battens, or it can be non-structural and rely on a timber or steel frame for support, in which case AS1684 - Timber Framing or AS4100 -  Steel Structures are also relevant.

Not being directly covered by the BCA or AS (on top of their natural resistance to trying anything new) also means that many builders or contractors will be reluctant to take on a reverse brick veneer construction.

Cheers,

  Glenn

Some initial research

Well, some quick browsing in the library has not turned up much useful information, but a deeper search may uncover more. We'll see...
   The internets have provided the usual plethora of information, opinion and outright nonsense, but the general consensus is that reverse brick veneer is a good construction method for our climate zone. The basic principle is that the thermal mass required for stabilising the internal temperatures in a home is actually placed on the inside and insulated from exterior temperature fluctuations, unlike the standard brick veneer home where the thermal mass is placed externally with insulation between it and the interior. The concepts of thermal mass are explained very well here. http://yourhome.gov.au/technical/fs49.html

Here is a nice detail picture of a reverse brick veneer construction for your viewing pleasure.



















Cheers,
   Glenn