Building a flame zone house in West Pymble on a steep site

"Location - are you on a busy road which needs traffic control ( we have one site on Pittwater road in North Ryde and for every delivery we have to get a Police and Council permit, traffic controllers and close down a lane) It adds up"


This certainly wins the first prize for perseverance.
How would you even estimate these costs (specifically, how would you know exact number of deliveries)?

Alex

You are so right. It's a tough one to calculate.

To be honest on this one we got it wrong so we have to wear the loss.

But as an example, the council fees are like $800 and then every delivery is over $600 ( thats a 4 hour minimum charge).

We are doing a strip footing slab which has lots of deliveries such as:

1. Pier pour
2. Strip footing pour
3. Brick deliveries 3 so far
4. Sand and cement 3 so far
5. Then slab pour

So just for the slab that's 9.

Then we will have timber, structural steel, hebel x 2, roofing x 2, gyprock, tiles, joinery etc etc etc.

This is one we didn't estimate correctly, but that's our error so we wear it.

In future, I would probably lean towards maybe a provisional sum of say $10,000.

We can just add that to the list of mistakes we have made in 2023

My partner was doing some head math the other day and the number in $'s was astronomical. If anyone is interested let me know and I will do a new topic on everything we have learnt this year.....the hard way. Hopefully help others learn from us.

Speak soon, really looking forward to seeing your build

Cheers

Simeon

Morning Everyone

Short update today.

The pool excavation was completed yesterday. A day quicker than I forecast.

So with rock being a provisional sum this will be a win for the client.

I have attached a photo of the completed hole. The top of the pool coping will be 540mm above the natural ground level.

Today we are having formwork and steel delivered and I believe the formwork crew is book for a Friday start.

I have a massive day today, so have to run

Cheers

Simeon

Happy Saturday Everyone

Quick update from site.

The focus this week and next is the pool. We need to get that in before the slab can commence.

So yesterday my formwork team formed up the pool. You can see the height of the pool in the attached photos.

We had a bit of rain, so this morning we drained water and laid a base of blue metal.

Monday the steel fixing crew installs all the reo. This will take a couple of days.

Then the pool plumber will run all their pipe work.

We then need an inspection of the formwork as we are close to the encased sewer.

Then the following week we shotcrete the pool.

To keep the job moving and to prove my wife wrong ( who works from home with an elevated view of the job site) we are programing a month ahead and booking crews in.

The plan for September is to have the pool and slab poured, so October framing can be smashed out.

As always, if anyone has any questions about this our their own projects, hit me with your questions:).

Cheers

Simeon

hi Simeon,

What was the rationale for the full blown concrete pool vs plastic shell as many do those days?

WBR,
Alex

Hi Alex

That is a very good question!

I used to be a fan of fibreglass pools, I have had two including one in my current home.

But in all that rain we had last year my pool started lifting up from all of the ground water underneath. Think of the feeling of walking on a waterbed.

I managed to get a pipe down underneath and I pumped out all of the water which helped but the shallow end still is noticabely deformed.

Then when you compare the cost between fibreglass and concrete ( our actual cost not with the mark up pool builders charge), the price difference is negligible. Yes concrete is slower, but I think long term concrete is a better outcome for our clients.

FYI my partner has a vinyl pool which he loves so we aren't adverse to other types of pools

cheers

Simeon

Hi Everyone

Nothing special to report today, just a daily update.

Yesterday the steel fixers started installing all the reinforcement. Should be finished today.

Attached are some photos that show the progress.

For anyone who is wondering how we know the type and how much steel needs to be installed and how it is to be installed, we have pretty simple instructions/plans which were prepared by the structural engineer. In this case we are laying the bars at 200mm centres.

We are missing a bench seat at one end and some stairs which should be installed today.

Have a great Tuesday

Simeon

Hi Simeon, what is the size of the pool? If bars are 10 mm, then you could simply put in SL102 mesh (or SL122 for 12 mm bars)?
Or even just pour the steel fibre concrete, without any reinforcement (but has to be certified by HelixSteel engineer, they do it for free).

Hi Alex

We need to use S12 which is a soft 12mm bar that can be bent up the sides and around the corners. The SL122 can't be bent.

I don't have any experience with the steel fibre, so not sure. Will ask the engineer next time I see him

Cheers

Simeon

Hi Everyone,

Nothing interesting to report over the last two days.

No works have been underway for 2 days whilst we have been waiting on the engineering inspection ( passed yesterday) and the Sydney Water S73 inspection ( booked for 11am today).

We need the Sydney water inspection as the pool sits partly on the encased sewer.

If we pass that today, next week we can do the pool plumbing and then hopefully pour by the end of the week.

Fingers crossed that all is good.

Have a great weekend and we will be back at it next week.

Cheers

Simeon

Hi Everyone

Quick update from site.

We poured the pool this morning. I think it looks great and the clients popped around mid pour to have a look and are super happy.

We added some spa jets onto the ledge so that should make the pool more fun in summer.

It took 10.5 cubic meters of concrete and took around 4 hours.

Given the heat today ( currently 31 degrees) in around 2 hours we need to start wetting it down with water. The instructions are to put heaps and heaps on it today and again for the next couple of days.

Now onto the slab, should have that down by the end of the month and then start framing in October.

Here are some photos

Cheers

Simeon

Hi Everyone

For the most part building a house is just a series of steps or processes.

Yesterday we took the next step which was the completion of benching.

We ended up bringing in 12 truckloads of soil to raise the site, and then compacted it to give us a firm base for the slab.

All of that previously exposed rock is now hidden and the site is really starting to take shape.

Monday we will do the piers. We need 3 inspections being Sydney Water again, the certifier and the engineer. Next Wednesday we can do our internal plumbing and then smash out the slab.

We are currently running around 10 days ahead of program so travelling quite well.....so far.

Here are some pictures from site.

Cheers

Simeon

Why soil, not sand? You would generally do not want to have reactive soil under the slab. Also, compaction with excavator is never enough. I believe the main reliance is on the piers now.

Alex

We do use sand, which is a 50mm binding sand between the soil and the slab.

Sand on it's own wouldnt be stable enough to support the formwork, think about building a sandcastle on the beach, it is very hard to stop them from collapsing.

The purpose of the piers is to bear the slab to rock, we have around 60 x 450 diameter piers.

Cheers

Simeon

Hey Alex, you should look up AS1726. Soil comprises all sorts of different particle sizes and compositions. Sand is actually a particle size range, as is silt and clay.

Agree that compaction from tramming isn't usually enough, but if the lifts are thin enough and moisture content is good then shouldn't be a problem.

Silt and clay are not self-draining, so they are not really facilitating the removal of water from the soil under the slab, and, therefore, if site is not maintained properly, the issues might still appear: even with piering and slab-in-ground systems the heaves are still possible on reactive soils (although slab-in-ground will be certainly less prone in comparison to slab-on-ground).

Using a deep enough layer of well compacted sand or gravel or combination of (usually 20-30 cm) under the slab and footings, instead of reactive soils, coupled with proper perimeter drainage, provides very reliable protection from water under the slab and in most cases can eliminate the necessity/requirements for piering even on highly reactive and unstable soils.

If slab-in-ground system is used, then footings can be also placed on top of 10 cm layer of well compacted sand and gravel and poured, however, with the above mentioned approach you don't really need slab-in-ground, slab-on-ground systems such as simple waffle pods or more advanced systems slab-on-ground systems used in northern countries such as Dorocell Foundation System or Dow Plate Foundation (it allows to build reasonably heavy houses on soils with bearing capacity of 30kPa or less!) can perform as well as typical slab-in-ground system on piers or even better, and at the same time, will significantly reduce the risks associated with maintaining the slab perimeter and protecting it from the water. If there is no soil freezing, there will be no specific need to maintain concrete path/protection around the house (other than aesthetical), no need to grade away soil and deploy clay locks and temporary downpipes during the building - the system is much more forgiving for typical building and maintenance mistakes and water flooding associated issues.

You would certainly spend extra on sand/gravel, proper compaction, and in some cases on extra concrete and reinforcement, but then you save on costs of piering, formwork, additional ground works and pours (such as excavation of footings and backfilling required for slab-in-ground systems as well as separate pours for footings and slabs).

Simeon, what is your estimate spend on slab, piering and footings including ground works and how big is the slab?

Yeah cool. I understand geotechnical engineering. All I was pointing out is the correct terminology, also, if the soil underneath doesn't come into contact with moisture, then the clay is fine to use for foundations. Depends what the engineer specifies and how deep pockets are I guess?

Alex

We budget around $280/sqm plus piers at $250 each but wont have the final figure until all drop edge beams and stairs are calculated at the end, and we know how much soil had to be removed as well.

Cheers

Simeon

Happy Monday everyone

A quick post update.

This is slab pour week.

Since my last post we have installed all of the in-ground drainage and formed around 80% of the slab.

Due to the complex nature of the slab in terms of the multiple sets of stairs, the large size and quantity of drop edge beams and the decision to suspend part of the alfresco to accomodate the pool equipment underneath, we have decided that it will be prudent to do the slab in 2 pours over 3 days.

So day one Wednesday we will pour the lower slab. Thursday the boys will finish forming the pool coping, install bondek and internal stairs and then Friday we will pour the upper slab, pool coping and stairs.

This will mean we need to waterproof the joint in the 2 slabs. We use a product called waterstop which expands and gives a tight seal when the concrete hits it.

In terms of program, we will lose 2 days. Slab pour had been programed for the 11th but will now finish on the 13th. But overall I think we will get a better outcome by doing it this way, rather than rushing a big pour in a single day.

The overall goal due to site access is to have all external concrete done now with the exception of the driveway which can be done at the end.

So still on track for a May finish.

Here are some photos from site taken yesterday.

Cheers

Simeon

Hi Simeon, so it is not a rafted slab I thought you have planned originally? Looks like waffle to me