Dear Colleague, Friend, Client
Let me begin the year with my first Blog on behalf of CTP Consulting Engineers. I plan to write a short Blog regularly giving some tip or advice on some aspect in the building sector. Don’t worry, this is not a space where I blow my own trumpet. Rather, I see this as a service to those around me.
So, this month’s tip is: Don’t try save money on consultants. A good consultant may be a bit more expensive but their experience will save you in the long run. One of the factors identified in South Africa’s current economic demise was identified as being the fact that engineering consultants have to tender on work. Thus the cheapest consultant is usually appointed for a job. The “successful” consultant will usually pull an old similar type of project from the shelf and get their draftsman or the cheapest person in the company to do the work.
The result is that contracts are poorly written, engineering designs are not innovative, and the product is usually 1.5 to 2 times more expensive than it could have been (if not more). Given that the correct fee for a consultant should be about 10 to 12 % of the contract cost, consultants are doing work at less than 5%. I have seen jobs awarded at 2.8% of the contract cost. For these low fees, the client is getting no benefit from the consultant and certainly he will be paying a premium that in the end is much more expensive than had the client paid the consultant a realistic fee.
On the West Coast I see the same thing happening! Builders and owners are trying to save on engineers fees. But it’s the very same engineer, who is tasked at designing the structure so that the house will be safe yet not over designed.
Some checks that you can apply to see if your house is over designed.
- Reinforcement steel for a house should be around 80kg per cubic meter of concrete.
- Is your engineer specifying Y16 reinforcement bars in your foundation? This could be seen as over design.
- What is the depth of your beams? Clever design of beams should ensure that the thickness is not more than the length divided by 250mm (for soft structures such as brickwork above) and 500mm (for rigid structures such as glass). Note that there are always exceptions to this.
- Does your engineer specify rib and block for slabs that are outside? On the West Coast outdoor slabs should be in-situ due to the corrosion on underside of the slab.
- Be careful if your Engineer specifies 20mm cover (the concrete protecting the outermost steel). The design codes are very specific in this regard where the exposure condition is more severe.
This month’s photo is of a structure that was founded on collapsible clay. There is a small pocket of geology on the West Coast which has collapsible clay and its quite isolated but unique, and you need to know that it’s there. In this case, the veranda was constructed and held in place by a two meter high retaining wall – not high in terms of house structures. When excavating for the foundation, reasonable care was taken by the builder to dig what he thought was normal practice. Little did the builder know that he was building on collapsible clay. The problem is that when the clay gets wet it cannot support the load and suddenly gives away. The result was that the clay suddenly started to fail and resulted in large cracks throughout the house. To prevent collapse it very important to keep the founding clay from getting saturated with water. Good drainage measures are required and the foundation must ensure that founding conditions are conservative.