Month: October 2012

Insulation – Heat loss Suspended Timber Floor

I have previously posted about the Heat Loss from a Slab Floor so how does that compare with a suspended timber, or particle board, floor?

Well its not as bad as you might think because the the space under the floor acts as a Buffer Zone between the room and the external temperature. (Unless you have got a pole house or a Queenslander.)

The main considerations are:

    1. The amount of external wall compared with the area of the floor, ‘ Perimeter to Area Ratio’ (PAR).
    2. The height of the floor above the ground (the calculations below are based on this height being 0.5m or less)
    3. The amount of ventilation expressed as m2/ m length of perimeter wall.

Heat loss Calculations

Perimeter to Area Ratio.

For a 10m x 10m house the PAR = 40/100 = 0.25

For a 20m x 5m house the PAR = 50/100 = 0.5

Ventilation

Low ventilation = 0.0015m2/ m length of perimeter wall

High ventilation = 0.003m2/ m length of perimeter wall.

The  table below provides some values of ‘U’ for the floor .

PAR

.2

3

.4

.5

6

7

8

.9
‘U’ low ventilation

0.4

0.51

0.59

0.66

0.72

0.77

0.82

0.86
‘U’ high ventilation

0.42

0.53

0.62

0.7

0.76

0.81

0.86

0.9

So for a typical single storey house of 20m x 10m

The PAR = 60 / 200 = 0.3

From the table ‘U’ is 0.51 -0.53 depending on ventilation

The heat loss from the slab = Area x ‘U’

= 200 x (0.51 -0.53)

= 102 -106 watts/degree C

The heat loss for this floor is 4 – 8% higher than the same sized slab on ground. The suspended floor will however have a lower thermal mass.

 

See Insulation for similar Posts

For Posts about Green Buildings see Sustainability

 

Building on Fill – Screw Piles

I have previously posted about building on fill using Concrete Piers.

Well one alternative to constructing concrete piers is to use Screw Piles such as the one to the right.

These are made from a thick steel tube with:

  • A cutting edge on the bottom.
  • A  spiral plate close to the bottom.
  • A keyway at the top to lock into the drive tool.

The pile is screwed into the ground using a drive tool mounted on an excavator.

Screw piles will normally be more expensive than concrete piers when only a few shallow piles are needed.

They can be cost effective, and fast to install, when a larger number of piles are required or soil disposal is a major problems.

Other advantages are:

  • There is minimal spoil to be removed from site.
  • You don’t have to worry about rain as much during the installation.
  • They can be easily installed when the base of the pile is below the water table.
  • They can be installed in very restrictive locations.

Edit based on question I received

If you are worried about corrosion normal screw piles are fairly thick steel to stand the driving forces (individual thickness of material may vary)

Typically corrosion for plain steel piles in natural ground can be in the range 0.12 – 0.3 mm in 10 years, although galvanised steel will be less.

See Ground Conditions for more about your new house foundations.

Arch Window Fail

This arched window is a shocker.

The arch is one of the most basic structural forms being simple and exceptionally strong.

Besides the curve of the arch the basic principle is the arch springs from a solid support, like this example to the right.

The first window has the arch supported by two cantilevers from the sides of the opening. In reality a complex structural form that is much weaker than the simple arch.

I think that for a normal domestic house simple arches or straight beams are the only way to go.

 

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

 

Insulation – Heat Loss Slab On Ground

Why is there less fuss about insulation under a concrete raft slab than ceilings and walls?…………well here are a few interesting facts:

  1. A thick layer of earth provides a reasonable amount of insulation.
  2. The soil contributes to the thermal mass of the structure which helps smooth out any temperature variations.
  3. The temperature of the ground below the surface varies much less than the air temperature. For Victoria a ground temperature range in the order of 13 degrees in winter to 22 degrees in summer is typical.

As a consequence the main heat loss from the slab is only from the edges of the slab rather than from the middle.

Heat Loss Calculation

When estimating the heat loss a key factor is the ‘ Perimeter to Area Ratio’ (PAR). Examples are:

For a 10m x 10m slab the PAR = 40/100  = 0.25

For a 20m x 5m slab the PAR   = 50/100  = 0.5

The  table below provides some values of ‘U’ for the total structure for various values of the ‘PAR’ .

PAR

.2

.3

.4

.5

.6

.7

.8

.9
‘U’

.37

.49

.6

.7

.78

.86

.93

.99

So for a typical single storey house of 20m x 10m

The PAR = 60 / 200 = 0.3

From the table ‘U’ is  0.49

The Heat loss from the slab  =   Area x ‘U’   =   200 x 0.49   =   98 watts/degree C

The ‘U’ value for this standard slab is similar to an Insulated  Brick Veneer  Wall.

A Waffle Pod Slab will have a slightly better insulation value but have a lower thermal mass.

If you want to install slab edge insulation see Insulating Your Slab.

 

See Insulation for similar Posts

For Posts about Green Building see Sustainability

 

Letter Box Fail

Can you see the mail box?

Do you think the people in this house don’t like to get post?………or do they like to give their postie a challenge?

The only way to deliver a letter is to push the bush aside.

The Your letter box post explains what you should provide.

Have you seen any unusual letter boxes?…..why not send me a photo?
 

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

 

Why Aggi Drainage Pipes Have Slots In The Base

A lot of people aren’t sure how drainage pipes work.

“Why doesn’t the  water run out of the slots at the bottom?” is a question that many people ask.

The pipes work on the principle that the soil/gravel around the pipe is water logged. This water drains into the pipe as the bottom of the pipe is below the  soil water level.

 

When the water drops below the  pipe  the water then runs through the gravel in the trench getting into the pipe further along the trench. (Diagram below shows a section along a pipe)

 

See Agricultural Drains for more information

 

Builder’s Bankruptcy – Finance

So the builder has become insolvent and the house is half built…………..what are the financial implications?

To finish a partially built project using another builder is going to cost more than if your original builder finished the project. For an idea of possible costs see Is The Insurance Enough?

Builders don’t like taking over half built projects and you aren’t in a buyers market so rates will be higher.

There should to be a couple of things that could help you:

  • Unless progress has been slow there is likely to have been a fair bit more work done than you have paid for since your last Stage Payment. – Under most contracts you don’t have to pay the builder for work completed prior to the bankruptcy until the house is completed and you can deduct any additional costs from any payments due to the builder, or his administrator.
  • Many states now require the builder to have insurance against insolvency. This insurance should allow you to claim up to a percentage (typically 20%) of the total contract value to have the house finished by another builder. This completion must be to more than the original specification.

I’ve spoken before about the importance of records and when dealing with completion of your house it is vital that you keep good records of all costs associated with the completion of the house.

Make sure your costs include all professional advice from lawyers, project managers, and other building professionals that you may need to engage.

If you want to find out more about Builders insurance Its worth looking at the QBE website.

A friend of mine whose builder went bust told me that the recovery added another $30,000 to the cost of the house………………How much did it add to your house?
 

For more legal posts see Contracts

 

Bankrupt Builder – Will The Insurance Be Enough?

I have previously talked about dealing with the mess when a builder goes bust.

To make the financial aspects clearer a worked example follows:

This is based on a contract for a house to be built for $300,000.

A typical building  insurance is 20% of the contract cost so it will be $60,000.

Assuming the builder becomes insolvent during the construction of the frame.

    • You should have already paid out
      • $15,000 (5%  Deposit)
      • $30,000 (10%  Base Stage Payment)
      • $45,000 Total Payments 
    • A new builder is going to charge more than the remaining $255,000 to finish the job as they will have to do quite a bit of extra administration and estimating. Say plus 20% ($306,000).
    • You have probably had some legal costs say $10,000.
    • The total cost of building the house is now:
      • $45,000 Initial payments for Original Builder.
      • $306,000 New Builder Cost
      • $10,000 Additional Legal cost
      • $361 ,000 Total.
    • You will be reimbursed up to $60,000 by the insurer so the total cost to you will be $361,000, which is $1,000 more than the original cost.

Conclusions

  1. As any new builder will probably charge a percentage on the remaining work its possible that if you are in the later stages of a build the insurance will be enough. If you are right at the start it may be best to walk away and start again with a new builder.
  2. If you have allowed the builder to charge more than the Standard Progress Payments there is more likely to be a shortfall in insurance money increasing the amount you will need to find.

 
For the next stage see Finishing Off, or to start at the begining go to If The Builder Goes Bust

 

Bankrupt Builder – Getting Finished

If your new house is under construction a typical procedure to finish the house with the insurer is:

  1. The insurer should appoint a building consultant.
  2. The consultant will  inspect the house and work out the scope of works to complete the house.
  3. The scope will be passed to you for acceptance.
  4. Three quote will be required based on the scope of works. These quotes can be from builders nominated by the insurer or you can seek quotes yourself from licensed builders.
  5. Once quotes are received the insurer will work out the amount of their liability and make an offer of the amount they consider appropriate.
  6. Assuming you confirm your  acceptance of the offer you can then accept a quote and  sign a new building contract with your choice of builder.
  7. The contract will include a new house warranty insurance policy which should be issued to you. (You  then have two policies; one for the original builders work, and one for the new builders completion work).
  8. Normally the insurer will make stage payments as required under the new contract on your behalf until the amount of the agreed insurance settlement funds are spent.
  9. Your mortgage provider will then continue making stage payments until the house is completed.

Remember its important to keep your mortgage provider aware of the progress of the claim and the proposed new building contract.

 

To follow the whole process start at  If The Builder Goes Bust

 

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