One solution to reduce the vulnerability of your house is to have your foreman properly trained. I now offer a training course that will lead to participants receiving the Diploma of Walbrent College. See article on Walbrent College for further details.
The Government of Barbados has several roles. One critical role is to regulate industries that are out of control. The residential construction industry is out of control.
We have been fortunate as a country to have had a Government with the vision to establish national building standards. The Barbados National Building Code was published 15 years ago, just before the current unprecedented building boom. The Code includes much of the technical advice that the following professionals normally provide their clients:
- Civil Engineers
- Structural Engineers
- Mechanical Engineers
- Electrical Engineers
Yet, for some inexplicable reason, the Government has not required that builders follow the national building standards. In my opinion, requiring builders to follow the minimum building standards does not require the proclamation of any new laws.
Last weekend, I visited some residential building construction sites hoping that I would see some improvement in the residential construction building practices. There was little good construction available for me to photograph, but the ubiquitous sub-standard construction completely filled my 1 Gigabyte memory card.
I cannot blame the building contractors, not the artisans they employ. I believe that they are simply doing the best that they know how. They need to be aware of and comply with the minimum national building standards. Who is to make them comply? I believe that is one of the Government’s roles.
Your medical doctor may be gravely concerned when she examines an X-ray of your chest, or she may recoil in horror when examining the blood laboratory test results, but you may examine the same and conclude that all is well. Why? Because you were not trained to interpret the evidence. I will try to help you to interpret the following photographic evidence from various construction sites at different stages of construction.
After setting out the building on site, the builder should excavate the area of the footings until he reaches a good bearing material. He has found a sound coral formation at a shallow depth. Very good.
The builder then builds form work to support the concrete strip footings. Very good.
But what is this? Oh please no!!!! (like all good horror shows, you get a peek at the monster before he is revealed in all of his gory).
The builder has placed a layer of marl fill on top of the good foundation bearing rock. He has therefore introduced the unnecessary risk of the building settling and the resultant cracked walls. He has also introduced unnecessary work which is translated into additional project time and cost. Quoting the national standard: “Footings shall not bear on fill material.” BNBC 2.504.4
Oh good grief no! The labourer has obviously taken great care in cutting this foundation trench by hand. However, he has stopped before finding rock, which is a mere 150 mm (6″) below this. He has introduced almost certain foundation settlement and the resulting cracks in the walls and floor, including any ceramic or stone floor tiles. It would not have cost any more to ask the labourer to excavate an additional 150 mm to the rock.
What the ??? The corners of the wall are not tied together properly. Let me show you how the building code specifies that it should be done.
Not tying the structural building elements together properly can result in the building shackling out and collapsing during hurricanes and earthquakes.
Oh dear! The builder cannot properly compact the 600 mm (2 ft) thick layer of fill – it should be compacted in 100 mm (4″) layers. In addition, placing that fill on the topsoil is almost guaranteeing the settlement of floors with the resulting cracked ceramic or stone tiles. The national standard states that this type of floor “shall be prepared by (a) removing top soil and any organic material; … (d) filling with granular material, if necessary, in layers of 100 mm …” BNBC 2.507.2
Compacting the top layer of fill only compacts the top layer of fill – not the underlying layers. Therefore expect settlement of the floor with the resulting cracks.
No vertical wall reinforcement, therefore the wall is vulnerable to collapse during an earthquake or hurricane. The National standard states “Loadbearing block walls shall be reinforced vertically with minimum 10 mm mild steel bars at 800 mm centres throughout the wall.” BNBC 2.405.2 (c)
Structurally unstable wall – no shear panel. Therefore vulnerable to collapse during an earthquake or hurricane. BNBC 2.405.8
If the wall reinforcement is not accurately located …
… then the wall is not properly reinforced and becomes vulnerable to collapse during an earthquake or hurricane.
This is gruesome. The national standard states: “No horizontal or diagonal chases for pipes or conduits shall be permitted unless specified by the designing engineer.” BNBC 2.405.3.
Pressure testing the water pipes for leaks – excellent!
Like I said, I have 1 GB of photos, but I do not have the time to transfer and comment on them all. I shall therefore adjourn here and resume on another post later.
Grenville Phillips II – Chartered Structural Engineer