Following on from my last post on construction for hurricane protection I have a few more tips but this time for wall construction using concrete blocks (concrete masonry units - cmu).
This type of construction is very common in the Caribbean and southern Florida due to the higher hurricane resistance of this type of construction.
In order to ensure that your hurricane resistance is maximised first and foremost a qualified structural engineer should work with your contractor to confirm proper practice is adhered to. As a client however there are a few things you can look out for as major red flags. it is vital that your roof structure is properly connected to your walls. This is usually done using a capping beam and reinforcement in the block holes approximately every 4th block hole in non loadbearing walls and in each hole for walls carrying heavy loads. If this is not the case on your site ask a question of your contractor and/or your engineer.
Your wall reinforcement should continue all the way to the foundation and tie in correctly there as well. It is also good practice to include stirupps in the corners and wall intersections and to reinforce and pour all block holes in these areas. This will cause your corners to act like columns and bring greater stiffness and strength to your structure.
To determine the amount of concrete required (or any of the materials that make up the concrete) we start with a calculation for volume.
A typical ground floor slab cast on solid ground (cast “at grade” in engineering terms) is between 4 and 5 inches thick or between 100 and 125 millimetres in metric.
Assuming a 4” thick floor first convert everything to feet and multiply length x width x thickness.
Volume of Concrete = 20’ x 10’ x 0.33’ = 66 cubic feet
You can also Try my Concrete Material Calculator on my calculations page here which can determine how much cement, sand and stone in cubic meters you would require.
Also bear in mind that a 94lb bag of cement holds 1 cubic foot (0.0281 cu. metres)
Here is a sample picture of my calculator below.
Click HERE to use calculator shown above
Concrete - What should a client/homeowner know