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.
“If you built to the minimum standards of the Code, then you would only have achieved the worst building that the law will allow.” Tony Gibbs
The minimum building standards in the Barbados National Building Code (BNBC) are for persons who simply cannot afford to do any better. To consciously build below these minimum standards is lunacy. You not only guarantee a homeless condition for your family after a major earthquake or hurricane, but your house is likely to attract expensive maintenance requirements within 5 years of occupancy.
Homeowners and building contractors familiar with the BNBC may be tempted to adopt only the minimum standards, in the mistaken belief that complying with higher standards is prohibitively expensive. I will therefore provide some guidance for home owners to achieve higher building standards at no or very little additional cost. This should translate into a more structurally stable house that attracts lower maintenance costs.
The Design Stage
It is easier and far less expensive to make changes to a drawing than to a built structure. Therefore, after you have received your drawings, critically review them. Ask yourself:
- Is it what we really want?
- Are we happy with the layout of the bathrooms and kitchen?
- Are we happy with the location of lighting fixtures and windows?
- Are we maximizing natural lighting and ventilation?
- Are we happy with the ceiling heights, and size and layout of the closets?
- Does the house have the necessary shear walls at each elevation?
Now, more importantly, does your spouse understand the drawings? If not, then use masking tape and layout the bathrooms, closets, kitchen and any other spaces as necessary. Resist the temptation to be pressured into prematurely approving the drawings because you are getting frustrated with the progress. Take your time to ensure that your spouse understands and approves the design locations and spaces.
The Construction Stage
Once you have approved the draughtsman’s or architect’s design, and the planning department has approved your development application, then your builder will set out or position your building on the lot so that he can excavate to find a stable foundation.
You should ensure that your house is accurately set out. Your site plan should show dimensions from at least two corners of the building to the nearest boundary markers. If it does not, then ask your designer to include them. Once the builder has set out the building, check that the corner-to-boundary marker distances are in accordance with those on the site plan.
A stable foundation can be achieved by eliminating the risk of the building settling. This means that you should excavate to a hard bearing layer. If you have reached limestone, then allow the excavator operator to cut into the rock at least 75 mm (3″) in order to remove the weathered top section. This can be done at no additional cost.
The Code specifies a 400 mm wide strip footing; however, builders normally use 600 mm, which is better. The vertical wall reinforcement is 10 mm diameter reinforcing bars at 800 mm centres. However, additional reinforcement needs to be placed at window and door openings and corners. Take your time and check the spacing and location of the wall reinforcement. Remember, it is your house. The additional cost to perform this check = $0.00. For clarification, there is insufficient reinforcement at the T-junction shown in the photograph above.
This is what happens when you do not measure carefully.
This is also what happens. I travelled around Barbados searching in vain for an example of how it should be done. The relevant autuorities need to arise from their slumber and acknowledge their responsibility to regulate industries that are out of control. The residential construction industry is clearly out of control.
Concrete must be compacted, and a vibrator is normally used to remove the air voids to facilitate this compaction. If concrete is not compacted properly, a condition called honeycombing results. This condition can allow air, water and chlorides to reach the reinforcement and facilitate the corrosion process. Compacting concrete should be done at no additional cost.
Concrete must also be cured to allow the chemical reactions that facilitate the hardening of the concrete and allow it to reach its design strength. Concrete can be cured by keeping it wet continuously for 3 days, or by spraying the surface with a curing agent. Ask your builder how he plans to cure the concrete. If he does not know what you are talking about, then you are in trouble. A house with a floor area of 280 square metres (3,000 sq ft) will require approximately 8 gallons of spray on curing agent, which costs under $300.
In beams and columns, bend the link ends into the beam and column in order to reduce the vulnerability to earthquakes and hurricanes. Insist on this task which can be done at no additional cost.
Since I could find no examples of how this should be done, I bent the link end inward …
and fitted it around the column’s main reinforcement so that the fabricator will know what to do.
This is where I found it last weekend. Why do I bother? Because I care.
Use the correct type of reinforcement. The British BS 4449 is stronger, less brittle, and can bend around smaller radiuses without fracturing. Since the American ASTM A615 is cheaper and weaker, you will need to use more of it to get the equivalent strength. Therefore the cost difference should be negligible.
Reduce the rafter spacing from 600 mm to 500 mm to increase the wind resistance of your roof. Your builder may not charge you any additional money for this; however, if he does, then for a 10 m (30′) long house, you will need approximately 6 additional rafters at approximately $80 each (2×6 Purpleheart).
Please do not rely on toe nails like this to keep your rafters in place during a hurricane. If you do not install BRC rater connectors or their equivalent, then prepare to be homeless. The cost of the rafter connectors will probably be under $100.
You should use hardwood or timber treated for insects. The additional cost of using termite treated Pine for a 10 m (30′) long house is approximately $220. The cost of replacing all of your roof timber structure could be approximately 100 times that amount.
Increase the frequency of roof fixings to 150 mm (6″) spacing at the hip ridges, eaves, and any gable ends. The additional material cost should be under $200. In the photo above, more fixings (like at the eaves) is required at the ridge, gable end, and another row at the eaves.
If you intend to use metal sheeting as a roof covering as in the photo above, then use 0.5 mm (24 guage) thick sheets. The 0.4 mm thick (26 guage) currently costs $2.01 per square foot of roof area, compared to the 0.5 mm at $2.46. Assuming a 1,800 sq-ft roof area, the additional material cost is $810. (The labour cost should remain unchanged). This is significantly less than your annual insurance premiums are likely to be.
This is what can happen if the roof sheeting is too thin and/or there are no spacer blocks under the profile ridge connections. Photo taken by author after hurricane Ivan in Grenada.
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