Category: Starting

Waffle Pod Raft Slab

A ‘Waffle Pod’ slab is now probably the most common Concrete ‘Raft’ House base.

It has generally taken over from the Conventional Raft Foundation.

It’s an example of composite construction with polystyrene pods forming the voids in the underside of the concrete ‘Waffle’.

This photo shows some of the pods, with the reinforcement fixed over them, prior to placing the concrete.

Advantages

  • Cost
  • No trenches resulting in:
    • Simpler excavation; and
    • Flat sub-base means site is easier to keep dry than trenches that collect water.
  • Waffle Pods bring house further out of ground so in an area that is wet the higher the better.
  • Better insulation from the ground meaning the floor will warm up quickly from cold when you put the heating on. (especially if you go for in slab heating)

Disadvantages

  • More susceptible to bad workmanship – If the pods move during placing of the concrete.
  • More susceptible to bad drainage which can lead to soil heave if building on reactive clay
  • Lower thermal mass so less suited to passive solar design.
  • Thinner slab (typically 75mm rather than 100mm) means may it not be as resistant to point loads such as jacking a car. Some people specify 100mm thickness for the garage floor.
  • A thicker overall slab may be needed if you want Floor Drains (To allow for the dropped floor in those rooms)

Problem Sites

If  your block has difficult ground conditions its still possible to use a waffle pod slab with:

 

Also see Ground Conditions

 

Building On Fill – Concrete Piers

Its not unusual for the Site Investigation Report for your new house to reveal loose fill materials above a more stable clay or rock.

It might also reveal the soil is in poor condition.

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

These are basically a hole that is excavated through the poor material 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 piers visible as 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, or weaker soil 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 over the piers 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 the estimated metresdepth 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.

 

Building a Long-Distance Home

Most people wanting to build a new home like to build it close by, but that doesn’t work for everyone.

Why build at a long distance?
Typical reasons for building long distance, including:

  • Building a ‘Holiday’ home.
  • Building a retirement home.
  • An investment property

There are lots of posts on this site about the process of building a house . . . but what factors should you take into consideration for a long distance house?

Building a good relationship with a real estate agent.

A local agent with a good appreciation of the local market is invaluable.

They can be the best person to direct you to the the better blocks for sale.

 Architect or Project Home Builder

If it is a basic flat block it might be worth looking at what the local project home builders are offering

If its a scenic block, which are often on steep slopes to get a good view an architect might be needed to get the best results

Making sure about the builder

Project builder or architect designed home? . . . . you are going to need a builder.

This is perhaps one of the most important decisions you’ll have to make when building your home.

After all, your putting your trust with this person for the whole build, so it’s essential to choose someone reliable who you can communicate with clearly.

Building at a distance you aren’t going to be able to visit the site as often as you would if it was just round the corner!

Make extra sure to check the credentials and references, and look into their past work to determine their level of quality.

Picking Your Own Building Inspector

It’s a good idea to have regular inspections during a build to make sure problems aren’t covered over.

If you don’thave the time to visit every 2-3 weeks a good builing inspector can be a good choice in ensuring a quality build.

Controlling Travel Costs

It is likely you are going to take many trips during the whole procees so its worth giving consideration to keep travel costs low.

Usually domestic air fares are cheaper on Tuesdays and Wednesdays and Sundays mornings are often the cheaper than othertimes.

 

 

Building On Sand

Building on sand at first seems to be an issue…… although I have heard it said that sand is actually the easiest ‘soil to build on.

If you live in West Australia there is a good chance that your house will be on sand so there is plenty of experience around .

Raft Foundations


Modern raft foundations actually cope with this any problems of building on sand quite well.

This is because the raft foundation spreads the load of the building over the whole area of your house which matches the weight carrying capacity of the sand very well.

This is much better than concentrating the loads on the wall foundations.

If you are building on sand a waffle pod raft foundation is probably the best way to go.

This is because the waffle pod doesn’t rely on any excavated trenches of the conventional raft slab to form the beams that gives the base its rigidity.

Soil Erosion

The main concern with sand is that it is very erodible so its important to make sure that the building site is flat and there are adequate retaining walls preventing the sand being eroded on the downhill side of the house………and eventually from under the house!

This is particularly the case if you are building a property with a sea view, you wouldn’t like to finish like this *house!

*photo courtesy of Australian Coastal Society

 

See Ground Conditions for more about your new house foundations.

 

Builders ‘SPECIAL OFFERS’

Have a look in the real estate section of the papers and you will see some builders are offering ‘Special Incentives’ for a limited period……………………..so should you rush in to take them up?

Well I don’t think it makes any difference.

The ones that offer incentives seem to operate on a cycle of offers something like:

$30,000 of Luxury Inclusions for $2,000

followed a couple of months later by;

Free Theatre Room 

then a few months after that by;

Free Air-conditioning and Landscaping

a little time later it’s;

Prices SLASHED by $30,000

then its back to;

$30,000 of luxury inclusions for $2,000

The truth of the matter is some of the builders add thousands of ‘marketing’ dollars to the price so they can make these ‘Special Offers’

The reason why they are limited is because they want you to sign up quickly rather than look around other builders houses.

I’m not saying that you aren’t getting a value for money house……….just don’t be pressured by the offer to rush in without thinking…….. They are not really ‘Free’, and there will be another different offer when the current one finishes.

For similar posts see Starting Off

 

Contracts – Provisional Sums

All new house building contracts will have a section for Provisional Sums.

These are used for work that  MAY be required, but the builder can’t provide an accurate estimate at the time of signing of the Contract.

The main area  for provisional sums is related to foundations where the limited information obtained during the Site Investigation may not truly represent the conditions found over the whole foundation.

A coule of examples are:

    • A rock item may be included even if the site is clay. This caters for any large boulders that may need to be removed.
    • An amount may be included for concrete piers if the amount of fill on site is hard to determine.

So the total contract price reflects the cost of building the house the builder will put in his best estimate of the overall cost of the build.

The provisional sum  will reflect the direct cost  of  those items to the builder only. (Overheads are included elsewhere in the contract price)

For example with a typical provisional sum item for removal of rock…… The builder will often include a figure of say $2,000 for excavation, and removal, of rock.

If there is no rock the contract will be reduced by $2,000.

Alternatively if the cost of excavator, labour and transport was $3,000 the final price will be increased by $1200. ($1,000 extra plus overhead percentage on the extra, typically 20%)

The builder is only allowed to add any overhead for profit and administration, to provisional sum expenditure items where they are above the original estimate.

Did you have any issues with Provisional Sums on your build?

See similar posts in Contracts

 

Travel Issues

It’s a Saturday morning and your partner says “Why don’t we go and look at some blocks that have been advertised in the paper?”

So you jump in the car and in no time at all you are at the developers office.

“That was easy!” you say………….but how realistic is Saturday traffic compared with a future weekday commute?

Once you move you may find you are spending a long time looking through your windscreen at traffic!

Before you make a decision perhaps you need to try the traffic out:

    • Arrange to meet your partner straight after work and see how how long it will take to get home in rush hour. Twice as long?……….or four times as long!
    • If you are really keen, then get up at 6.00am, and drive to the site. You can then see how long it will take you to get to work.
    • A quick check might be to use Google Maps to estimate journeys for a few work days
    • You might  also try out the public transport.

Were you surprised how long it took to get to work after you moved?

See Blocks for more information on buying land.

 

Building On Clay Soils

Clay is a fairly common soil type.

Although it is quite suitable for building one issue is that some types of clays (‘Reactive’ or ‘Desicated’ clay) that shrink or swell depending on the level of moisture.

This can lead to the following problems:

Subsidence

Subsidence or settlement is when the building foundation drops, caused by the loss of support of the site beneath the foundations.

This is usually caused by shrinkage of the clay due to it becoming drier.

Typically this is due to tree roots spreading under the building and taking the moisture out of the clay.

Prolonged drought can also cause soil shrinkage beneath a building.

Soil Heave

Heave is the expansion of the ground beneath part or all of the building.

Expansion pushes the foundations, and thus the building upwards.

This is a photo of a boundary wall with inadequate foundations.

Due to soil heave the right side of the wall has lifted by over 100mm causing cracking of the mortar joints, and a brick.

Although the mortar joints have recently been repointed you can see they are no longer straight.

The most common cause of soil heave is building is when the clay becomes wetter and starts to expand.

Common reasons for the clay to become wetter are:

  • Water seeping down the side of the house (In areas of reactive soil a normal requirement is to have a 1m wide footpath round the house)
  • Poor site drainage (No drainage, blocked drains, or leaking water pipes)
  • Removal of trees (This means the drying effect of the roots has been removed)

A couple of danger signs of future soil heave issues for a new house build are:

  1. If building after several years of drought the soil may be excessively dry and therefore more likely to become wetter when the drought breaks.
  2. Removal of trees immediately before building.

Summary

There is no reason why you shouldn’t build on clay soils but you need to ensure that;

  • You have chosen an appropriate construction method (Brick Veneer is usually better than double brick)
  • There will be minimal soil moisture change when the house is built. (see this link:  Protecting Your Slab)
  • If you need concrete piers see the following link: Building on Fill.

To find out more about the soil on your block click on this link: Soil Classification

 

 Lots more information in the anewhouse at this link: Guide to Buying a Block

To find out what soil is on your block see this link: Site Investigation

 

Battleaxe Block

Have you seen a ‘Battleaxe Block’ advertised and wondered what it is?………….Well it is a block that only has a 3-4m frontage on the street.

Often these blocks are as a result of subdividing a long block with the rear block then becoming the ‘Battleaxe block” – coloured red, as in this plan.

In the plan the existing house has been retained.

You will also often find cases where the original house has been demolished to allow 2 blocks to be sold at the same time.

Another way of splitting a large block is a ‘Small Strata’ Development. (see this link: Small Strata)

What  are the issues with Battle Axe Blocks?

Driveway

To get access to the site you will require at least 20m of driveway and perhaps a turning area. This will have a substantial costs. I would allow at least $600/m run of driveway for a temporary gravel driveway during construction and for final concrete at completion.

You may save on this cost by going for a Small Strata Development with a common driveway, instead of a Battle Axe Block but:

  • Getting agreement from your neighbour to use the access for the construction can be difficult.
  • In my experience the best way to have good relations with neighbours is minimise causes for dispute. Sharing a driveway means that your parking options are limited.
  • Looking after the shared driveway is like some of the ‘Community Title’ issues (see this link: Community Title )

An advantage of that long driveway is if you put a gate with a childproof lock at the front it gives a safe area for toddlers to play.

Additional Service Costs

You will be need to bring in some if not all of the following service for an extra 20-30m.

  • Power.
  • Phone.
  • Water, could be two services if you want recycled water.
  • Gas, if it is available.
  • Storm water drainage, can be a problem if inadequate fall and property drains to road.
  • Sewer, usually this is at the back of the block but check before you buy.

Additional Building Costs

I have heard additional building costs of more than $15,000 for battleaxe blocks because of a restricted site (see this link to find out more: Restricted Site)

In Conclusion

I am not saying don’t buy a Battleaxe Block, just make sure that you think carefully about the implications.

What issues have you found with Battleaxe blocks?

 

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

See Blocks for more information on buying land.

 

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

 

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