Damp Proof Course (DPC)

The purpose of the outer skin of a building is to keep moisture out of the house structure.

A  damp proof course, in the brick veneer example shown below, has two purposes:

  • It prevents moisture from the ground rising up through the external brick skin. (This moisture can cause effervescence which stains the brickwork)
  • It ensures that moisture that penetrates the brickwork runs down the wall and is discharged to the outside through the weep holes.

The DPC, which is usually polyethylene, should be the full width of the brickwork. The other edge of the DPC should be fixed to the face of the bottom plate of the wall frame.

The drawing shows a DPC 75mm (one brick) above the ground. This is an absolute minimum and 150mm is preferred.

 

For other DPC details see this Clay Brick link.

For other similar posts see Construction

 

Plasterboard

A lot of people say Gyprock, but this is really a manufacturers name, so the correct name is Plasterboard.

So plasterboard is plasterboard right?……………………Actually wrong there are quite a wide range of plasterboard options available.

Perhaps you should consider alternative products if you are having a custom house built.

Even if you are using a project builder it might even be worth seeing if you could upgrade the plasterboard for certain rooms like the Home Theatre.

Here are some of the plasterboard options available, at extra cost:

  • Reduced Noise Transmittance Uses denser materials to increase acoustic resistance.
  • Improved Noise Absorption Mainly for use on ceilings to avoid that echo effect you can get with rooms with lots of hard surfaces.
  • Increased Impact Resistance Could be just the thing for children’s rooms and staircases.
  • Better Water Resistance Just the thing for bathrooms and laundries.
  • Higher Fire Resistance A good option to help protect your house from a garage fire.
  • Flexible Boards Good if you prefer gentle curves rather than square corners.

Want to find out more………… both ‘Gyprock’ and ‘Boral’ have comprehensive websites with lots of information.

 

For similar posts see Selection

 

Why Double Brick

Double Brick is the most common method of construction in WA.

Construction consists of two panels (sometimes called leaves) of masonry with a cavity between them. The panels are connected by steel ties at regular intervals.

A better description would be Structural Masonry, Cavity Construction. which also includes using limestone, rendered brick and concrete block for the external face, and brick or concrete block for the internal leaf. (The photo shows a brick external leaf connected to a concrete block inner leaf by a wire tie)

The purpose of the cavity between the outside leaf of brick and the inside leaf is so that moisture doesn’t penetrate into the home. In more sustainable homes this cavity is partially or fully filled with insulation.

Internal walls are usually a single brick thickness and generally use a 2nds brick or concrete block that is plastered or lined using a lining board.

Advantages

  • It is extremely durable requiring very little maintenance.
  • The mass of the brickwork can help moderate the internal temperature of the dwelling
  • You can place a heavy fixing anywhere on the walls.

Disadvantages

  • More expensive than Brick Veneer.
  • Not as well insulated.
  • The house will take a long time to warm up in winter or cool down once it does get hot.
  • Likely to crack if subjected to ground movement.

 

Also see:  Brick Veneer.

See this link for more posts:  Bricks

 

Why Brick Veneer?

Brick veneer is probably the most common method of construction in Australia.

However if you live in Western Australia you will find Double Brick is more popular in that state.

Although brick veneer is the usual term these comments will apply to all ‘Masonry Veneer’ construction which includes external walls of:

  • Brick.
  • Block work. including Light block such as Hebel.
  • Rendered brick / blocks.
  • Stone.

A Masonry veneer structure has two main components:

  1. The Frame. Can be either Timber or Steel. This is the main structural component of the house supporting the roof, and if required the upper floor. This is usually ‘wrapped’ as in photo above.
  2. The Masonry Veneer. Although this looks solid it really only supports itself, and relies on ties to the frame to keep it stable. It provides a weatherproof ‘skin’ to the building.

So Why

  • Gives a solid look to the house.
  • Lower cost than solid brick
  • The prefabricated frame allows the frame to be erected quickly allowing the builder to get the structure weatherproof.
  • Easy to insulate.
  • Lightweight internal construction which means it can be cooled or heated up quickly when you get home.
  • Relatively easy to make internal alterations at a later date.
  • Better able to deal with soil movement in ground conditions such as Clay Soils.

Problems with Brick Veneer:

  • Termites if using a timber frame.
  • Not as good as brick in preventing noise transmission.
  • Doesn’t have much Thermal Mass to balance extremes of temperature or help with Passive Solar Design

If you don’t like Brick (Masonry) Veneer tell me why not!

 

The most appropriate Brick Dimensions will make the walls easier to build.

 

High Ceilings – Unexpected Effects

Quite a lot of people go for  Higher Rooms because it does give a more impressive interior effect.

Something to bear in mind is that it can effect the external appearance of the house by making the windows look small.

This photo of a house under construction  illustrates this. The additional courses of brickwork between the head of the window and the fascia board looks a bit incongruous.

The alternatives to deal with this for this single storey house are:

  • Make the windows taller.
  • Have Overhanging Eaves which brings the fascia lower.

With 2 storey houses the effects of the higher ceiling can be even more pronounced.

If you think you may go for higher ceilings it’s worth thinking about how the house will look from the outside.  If the display house you saw has high ceilings its easy to check, otherwise you may need to see a drawing before you make a final decision.
 

The Design Section has more posts on planning your new house.

Or see the ‘Selection / Pre-Start Guide’

 

Want a Flat Roof ?

When thinking about a flat roof for your new home my advice is…..a roof can be:

  • Flat.
  • Inexpensive.
  • Have a long leak free life. 

PICK ANY TWO!

Sounds harsh but my experience, and others I have talked to, confirms this opinion.

My personal experience  with a flat roof was my parents house which had a pitched roof for the main house, but a flat roof for the garage.

After about seven or eight years the garage roof started to leak. Following 4 attempts to fix it they bit the bullet and had a pitched roof put on the garage. No more  problems in the next 30 years.

Yes, I know many multi-storey building have a flat roof without problems but with these tall buildings the roof is a small proportion of the total cost and so the builder can invest in a more sophisticated, and expensive, roofing system.

In your one or two storey property the roof will be a much bigger proportion of the total cost.

Most builders go for a low cost, low tech roof to keep the cost down. If it’s flat it will probably last until the guarantee period runs out and then you could be faced with ongoing repairs.

These comments will also apply to balconies over habitable rooms which are also prone to leaking.

If you do decide to have a flat roof you will need plenty of large downspouts (See Roof Choice – Risk)…………..otherwise you could have several cm of water on your roof in a storm, which will really tests the waterproofing.

 

Want Tiles or a Colorbond Roof see  What’s On The Roof

 

Building On Fill – Concrete Piers

Its not unusual for the Site Investigation for your new house to reveal fill materials on top of the more stable clay or rock.

Even if there is no fill the builder may need to level a sloping site using ‘Cut and Fill’ methods, or the top layers of soil are generally poor.

To deal with the problem of building on poor ground concrete piers are commonly used.

These are basically a hole that is excavated through the fill and into the top of good ground. The hole is then backfilled with concrete to the level of the underside of the slab.

When they are finished you have a flat site with concrete pads (like the photo below), ready for the slab to be constructed

You don’t have to have Concrete piers over the whole site, just the parts where there will be fill between the bottom of the slab and the stronger soils.

The following diagram shows a typical slab on a cut and fill site with piers excavated through the fill to the good ground.

See the following link for an alternative to Concrete Piers: Screw Piles.

The Slab is likely to be either a Waffle Pod Raft or a Conventional Raft Slab

When the site investigation indicates fill the builder will often put in a Provisional Sum for so many metres of concrete piers.

At the time of construction they will drill down to  good ground in the fill areas and calculate the actual metres you will need to pay for.

If your whole house is on ‘Controlled Fill‘ You may not need to use concrete piers.

 

Lots more information in the anewhouse Guide to Buying a Block for only $4

See Ground Conditions for more about your new house foundations.

 

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