Journal of Self-Built Private House Construction – Part III – Construction Methods

Part 2 of the journal

In the previous part of the journal, I wrote about choosing a construction method in terms of business engagement: turnkey contractor, project manager, or full self-management of the construction. In this part, I will talk about construction methods in terms of the physical aspects, the blocks, the rebar, etc., that will make up the house.

If you have chosen a general contractor, then this part of the guide is presumably redundant for you because the choice of contractor dictates the construction method – that which the contractor specializes in. If you choose a project manager or decide to build yourself, the next step immediately follows the deliberation regarding the construction method itself. What will be the material from which your walls are constructed? In the past, the answer to this question was simple. Walls were built from blocks. Today, there are several construction methods from which we must choose.

I will delve into the financial planning of the construction later, but for now, one of the first dilemmas regarding construction is the overall budget in a rough estimate. As we began our inquiries, we saw proposals for all sorts of construction methods that on the face of it are supposed to yield a house at a significantly lower cost than "regular" construction. Wood construction, prefabricated construction, new method X, and new method Y, etc.

It is important to remember that no matter which construction method is chosen, the term "construction method" refers solely to the shell—the outer structure of the house—the walls. The frame accounts for about one-third of the total cost. In other words, even if we find a construction method that reduces the cost of the frame by 50%, the impact on the final price will be 50% × 33% = 16.5% of the total cost of the house. This makes sense. Even in a wooden house, a panel house, or any other method, you still need the same toilets, the same sinks, the same electrical wires, sewer and water pipes, and of course the same concrete-cast safe room. Therefore, one of the first things I learned is the need to take with a grain of salt ideas about significant cost savings by choosing a construction method. It’s not that 16% out of 2 million (about 300,000) is a small amount of money, but it’s a much smaller gap compared to the promises.

The table below was prepared by our project manager, Ronen Kolan, and compares three alternatives we considered:

1. Ytong block
2. Block Ravvid 3rd Gen
3. GSB

The first two alternatives are standard alternatives where a worker lays blocks on top of each other, but there is a difference in the technology used to build the blocks and their insulation properties. This was important to us because of the hot climate and the desire to live with minimal need for air conditioning. The third alternative, GSB, is what is known as light construction or industrialized construction. In this type of construction, there is no worker on site laying blocks on top of each other; instead, a factory prepares all the walls in the factory, and only assembly is done on site. It's like a large IKEA cabinet.

criterion	Italian	3rd Generation Rabin	GSB
Price (NIS per sqm)	200	250	300
Construction Accuracy	Accurate	Very accurate	Very accurate
Design	Right angles only	Right angles only	Square and rounded corners
Strength	Medium	Weak	Very strong
Crack resistance	Weak	Very weak	Very high durability
Thermal insulation (M+R)	According to the standard	Highest, Level 3 (No meaning to values above 2)	Highest, Level 2.5 (values above 2 have no meaning)
Thermal mass	Low because there is no external Styrofoam insulation	Medium because the thickness of the block between the insulation and the inside of the house is small	High due to a combination of external polystyrene insulation + cast concrete mass.
Human Sensation - Thermal Comfort	Good	Good	Very good.

If each criterion in each row can be scored from one to three according to the success of each method in each characteristic, we will get the highest score for the GSB method. Although this method received the highest score, we ultimately chose to work with third-generation Rabi blocks:

It can be seen that the block is wider than usual with a layer of Styrofoam inside the block for improved insulation. There were several reasons for choosing the alternative that received the second-highest score out of the three methods, rather than the highest score:

1. The image shows the roof of the first floor, upon which the walls of the second floor will be built. I marked with red arrows the walls of the first floor that are actually underground. The part that is underground cannot be ventilated in any case by GSM, and the meaning of choosing this method was actually a combination of two methods.
2. We met with the manager of the company that markets the GSM method. Honestly, we just didn't have good chemistry. It happens. It certainly doesn't say anything about him or the method.
3. Some of the criteria seemed irrelevant to us. For example, exposure to future cracks. Our house was built on exceptionally stable rock. My parents' house, located in a neighboring area, hasn't suffered a crack since its construction over fifty years ago, and that was with less advanced construction technologies.
4. While thermal resistance is very important to us, when we studied the subject, we saw that the main thing is actually roof insulation, and specifically in our house, wall insulation has less importance because we chose to have very large windows on the upper floor (the lower floor is mostly shaded).

Large windows in the living room and kitchen intended.

So, after the house was planned, the construction method was chosen, the project manager was chosen, thanks to the bill of quantities the frame contractor was chosen, the time has come for the economic planning of the project. I chose to include the chapter on planning in Chapter D, but this is of course not accurate in terms of the overall project management. Economic planning and execution accompany the entire project. For example, even before planning, one needs to know What is the project budget And this is done through the financial planner even before the meeting with the architect, so that the planning is within budget.