Retaining Wall Fairness

In Western Australia subdivisions are usually completed with retaining walls in place on the boundary so that all blocks are level.

For the rest of us if we are faced with a sloping site a retaining wall may be needed before you can build…………..but who pays?

Here are a few examples

Block A is sloping down towards the boundary and Block B is fairly flat

Block A has to build up their block and should be the only one to pay. The wall should be within their block.

Block A is fairly flat and Block B Falls away from the Boundary

Block B has to excavate their land and should be the only way to pay. The wall should be within their block.

The slope affect both Blocks A and B

As one block has to be build up and the other has to be excavated both should share the cost. This however can a fairly complex with some of the issues being:

  • Should the overall cost be apportioned if one site has to be built up by 1m while the excavation needed is only 0.5m.
  • The location of the wall particularly on slopes.
  • Fences on the wall
  • What happens if you are keen to build but the other block is unsold or the owner is in no rush to build.

Each block having their own wall may be a solution, however these can’t be too close together (See this link for more: Retaining Wall) which may be an issue if you need to site the house near the boundary.

In cases like this you really need to make sure your lawyer sews up a watertight agreement on retaining walls before you buy the block.

This link: Understanding Retaining Walls gives an understanding of the technical issues


Agricultural Drains

Agricultural drains (often called aggi drains) are used to:

  • Drain waterlogged ground.
  • Avoid soil Heave by keeping your foundations dry (see this Link: Protect foundations)
  • Keep the soil behindRetaing Walls dry. (see this link: Retaining Walls)

In the old days agricultural drains used to be constructed out of short lengths of clay pipe butted together without proper joints. The water seeped into the pipe through these butt joints. If you are building on a demolition site you may still come across these pipes.

Nowadays agricultural drains come in two types:

  • White slotted UPVC pipes with longitudinal slots which come in straight lengths (usually 6m long).
  • Black corrugated UPVC pipes with lateral slots that come on coils of various lengths.

For domestic jobs the black corrugated coils are probably the easiest option.

DON’T get the pipes with a Geotextile ‘Sock’ around the Pipe (see this link:  Geotextiles Around Drainage Pipes)

Laying Aggie Pipes

You don’t need to be a plumber to lay agricultural drains in your garden. Some advice for laying the pipes are:

  1. The pipes should be laid at a gradient of no flatter than 1 in 100 (1cm in 1m) to the point to which the flow will be directed. A gradient of 1 in 50 is better!
  2. When excavating a trench for agricultural drains you need to dig the trench at a width of at least twice the width of the pipe and at least 25mm deeper than the level of the pipe.
  3. Lay 25mm of 10mm gravel in the trench keeping it at the set gradient.
  4. Lay the pipe along the top of the gravel keeping it as straight as possible.
  5. Fill the trench with 10mm gravel to 100mm below ground level.
  6. Fill the last 100mm with topsoil.
  7. Make sure you have a silt trap before the point where you connect to the point of discharge.(see this link:  Silt Trap)


Some people confuse concrete with cement, but cement is just the ‘glue’ which holds the other constituents of concrete together.

There are a range of different cements but these are the three you will most commonly come across:

General Purpose Cement

This is consistent, versatile and cost effective which makes it a good choice for most building works. It can be used for Domestic concrete slabs, driveways and footpaths

Trivial Fact -You may hear standard cement referred to as Portland Cement – This is because the finished concrete has an appearance similar to stone quarried from Portland in England.

Sulphate Resisting Cement

Sulfate Resisting Cement is a blended cement designed to improve the performance of concrete where the risk of sulfate attack may be present. It also provides improved durability for concrete, and the steel reinforcement, in most aggressive environments,

Although it has an additional cost it is best for:

  • Geothermal areas and soils containing sulphates
  • Saline Areas
  • Area that are frequently wet such as concrete swimming pools

Rapid Set Cement

Normally found in dry premixed concrete mixes. This is a cement with various additives that speed up the reaction to give an initial hardening within 15 minutes.

Any speeding up of the cement reaction time leads to lower final strength. This makes this product good for things like setting fence posts………… but NOT for significant structural applications.

Water Cement Ratio

One of the most important issues with cement is ensuring the ratio of water and cement is correct as this affects both the final strength and the durability. For instance:

  • Water cement ratio 0.5 (10L water to 20kg cement) is needed for high strength 35MPa.
  • Increasing the Water cement ratio to 1 (20L water to 20kg cement) will reduce the strength to 10MPa.

To ensure they don’t add too much water premix companies usually measure the water content in the sand and gravel piles and reduce the water content accordingly.

For more information see Concrete.


Architectural Bridge – Fail

It’s not a new house but it is architecture and my wife or I use it every day.

It’s the footbridge at Footscray Railway Station.

Looks fairly impressive and very modern with its round shape………….So why is it a Fail?

Well you would think that one of the main purposes of this bridge would be to keep you dry as you walk across it on rainy days.

This is where it fails, most of those transparent panels you can see in the roof are in fact steel plates with lots of holes drilled in them.

Consequently when it rains you get as wet walking across the bridge, as if there was no roof!

Not only that but these panels are over the stainless steel handrails on the stairs. If you stumble on the stairs its no use relying on grabbing the rail as with the water streaming down them they are as slippy as ice!

A triumph of architecture over practicality!       A truly Epic Fail!

For more Fails and Unusual Houses go to What the………………….?


Standard Building Contract or ‘Owner Builder Contract’

Some small builders may suggest they can package build a house cheaper for you if you become an ‘Owner Builder’*.

* Not be confused with True ‘Owner Building’ where you have the skills and propose doing a lot of the work yourself

Here are 8 reasons why you should think very hard about doing this:

  • You remove the protection of the standard building contracts.
  • The whole exercise is about removing responsibility from the builder if this is their attitude at the start how confident are you they are going to take responsibility for any problems during the build..
  • Do you fully understand the responsibilities and risks which can include extra costs that can blow your budget.
  • Do you have all the knowledge, skills and time to manage the build properly.
  • You will have to take a course (May be available on line) which is going to take time. This will only give you the most basic understanding of the process.
  • Most banks are very reluctant to lend to owner builders so finance is going to be an issue.
  • You won’t have the advantage of any of the standard builders guarantees which means that if problems arise later you will have to meet the full cost.
  • When you want to sell many people can be reluctant to buy an Owner Built House without guarantees.

I have heard of several cases where this type of job went wrong but it may be successful for you.

For Similar Posts see Choosing a Builder


Round or Slimline Tanks?

In addition to the standard round tanks there are a whole range of alternative rainwater storage tanks available.

One popular shape is the slimline tank which will fit in a narrow space. I have even seen a row of them used as a boundary fence.

Before you make a choice it could be worth thinking about finding out if you can find room for a round tank.

Round tanks cost less because they are easier to make and use less material. Typically the cost increase for a slimline tank over a round tank of the same volume is at least 50%.

A comparison from my local Masters store:

  • $800 for a Slimline 3,000 Litre tank
  • $500 for a Round 3,000 Litre tank

If you haven’t the width to fit a 3000L tank you could perhaps look at getting two round 2,000Litre tanks for the same price as the 3,000Litre Slimline tank.

Other advantages of the round tanks are they are a lot stronger, and easier to clean out.


See this post to find out How Much Rainwater Storage You Need


Consideration of Others – Fail

Here is something that really gives me the 5H!T5 and it seems all too common on newer housing estates.

Some Bogan leaves his car parked across the footpath because they are too lazy to walk another 5m.

No consideration that they have to make people walk in the road.

Is it my imagination?……….. or is it really true that 90% of the people that are guilty of this trick drive Holden Commodores?


What do your neighbours do that annoys you?


For more Fails and Unusual Houses go to

 What the………………….?



Understanding your Survey Plan

I’m used to look at survey plans but I do understand that most people struggle to understand them. Here is a quick guide to help you understand the survey plan for your new house.

The plan below shows a survey plan for the block previously mentioned in the Title Plan Post. It doesn’t include the easement to make it easier to see the other details.

The bearing and length of each boundary are the same as the title plan in the format.  For example the North boundary is at bearing of 92 degrees 0 minutes 15 seconds (92° 00′ 15″) and 38m long.

A North Point has been provided.

The footpath along the front of the block and the nature strip crossover (constructed by the developer is shown, as well as an electrical pit.

TBM stands for Temporary Bench Mark. This means the surveyor will use this feature as the level on which all other level information such as slab levels will be based. Its normal for the TBM to be set at a round number typically either 10.000m or 100.00m. Usually the only time the TBM’s actual height will be the correct height above Sea Level (Australian Height Datum) is when there is a risk of flooding and the floor level will need to be above the 100 year flood level.

Once the TBM has been set the surveyor calculates the surface levels of the block. This is shown by contours, (shown dashed) which are lines of equal height. The normal contour interval for residential block surveys is 0.2m intervals and each contour is labelled with the height it represents.

In addition to the contours the surveyor will show spot levels at the corners and sometimes in the middle of the block. These are marked with a ‘+’ and a height.

From this drawing you can see:

  • The lowest part of the block is the South East corner at 100.00m
  • The highest part of the block is the North west corner at 100.85m
  • The block slopes upwards from the front at approx 0.53m. (around 1 in 70)
  • The block slopes upward in a Northerly direction at approx 0.30m (around 1 in 60)
  • As the contours are roughly similar spacing from each other the slopes are fairly constant.


In summary although there is a slope on the block it isn’t too severe so the site costs for dealing with the slope could be around $4- $6,000.


For more see Blocks


Door Opening

One of the small things that can really make a difference to your house is how doors open……..but its one thing that is frequently forgotten.

This sketch shows a typical bedroom and ensuite layout. (I know it doesn’t show the wardrobe but I’m trying to keep it simple)

A couple of things you need to think about are:

Into The Room Or Not

You will see as usual the doors to open from the corridor, into the room or into the en-suite from the bedroom as in this diag.

Particularly in the case of bathrooms and en-suites it makes a lot of sense for the door to open into the bedroom as this makes a lot more usable room in the bathroom.

It also minimises the risk of sending my wife flying if I open the door while she is at the mirror putting her make up on.

In the case of separate toilets its actually much safer to have the door open outwards.


Left Or Right Handed

How to tell – When you look at the door from the side it opens towards, and you can see the hinges…. which side are they on? That is the hand of the door.

Looking at the door to the bedroom you will see that the door is hinged on the right as you look at it from inside the room.

This works well as the door opens against the wall. Having the door hinged from the left side doesn’t seem much different, but it means you have to walk round the door to get out.

It seems minor but in our last house we got one door wrong and it annoyed us every day for 6 years.

You need to get the door opening sorted out before you can finalise your electrical plan as it will affect which side of the door you put the light switches.

Once the wires are installed and the drywall installed changing the door direction can be a major cost.

More on doors including 24 pages of Check Lists for your new house choices in the

‘Selection / Pre-Start Guide’