Countries in Central America and the Caribbean are vulnerable to hurricane disasters which can leave many people homeless and hungry. With improved house design and construction, homes can withstand high winds, providing adequate and safe shelter during a hurricane event.
New Construction
For construction of a home 3000 square feet or less.
House Location
If possible, make sure house location is above known flood plain!
Build in areas that provide natural shelter from winds (build on leeward side of hill; tops of hills are not protected).
Do not build on steep slopes, especially if they face the sea.
If you must build on steep slopes, dig into the hill to have flat, solid ground on which to build.
Make sure the cut part of the hill slopes gently enough to avoid erosion (usually 33-37 degrees from horizontal).
Plant grass and shrubs on the cut part of the hill to slow down erosion.
House Shape
A square house is the sturdiest design for high winds.
Rectangular houses with length to width ratios of 1 : 3 or less are also recommended.
Other house shapes may create weak spots at inside corners.
Foundation
NOTE: This foundation is designed for block masonry walls.
The foundation is made of reinforced concrete, using reinforcement bars (rebar) of 1/2 inch mild steel (it is easier to bend).
Exterior footings are 12 inches deep and 16 inches wide. Rebar in the footing should be placed 3 inches from the bottom. Rebar also runs vertically through the
exterior walls, with wall rebar spacing at 32 inches apart. The bottom end of the wall rebar should be fastened to the rebar in the exterior footing.
Interior footings should be 7 inches deep and 18 inches wide. Rebar at 3 inches from the footing bottom is also needed. Wall rebar is fastened to the footing rebar at tees and corners (discussed in the Wall Construction section).
The rest of the slab is 4 inches thick with rebar running horizontally through the slab at least 1 inch from the slab surface.
Wall Construction
Walls are made of concrete block, rebar and infill concrete. Concrete blocks 6 - 8 inches thick are used for exterior walls. 4 - 6 inch thick concrete blocks can be used for interior walls. The concrete block used in this design have two openings that create vertical spaces within the walls (see diagram below).
Every 32 inches in the exterior walls, spaces are filled with rebar (which is anchored in the foundation and to the rafters) and infill concrete. Use cement between blocks to bind the surfaces of the blocks to each other. 3 reinforced spaces (rebar and cement) are needed at interior wall corners while 4 reinforced spaces are needed at interior wall tees.
Spaces should be reinforced next to door and window openings as well.
Roof Shape and Construction
Roof shape and construction are extremely important to house survival of a hurricane since high winds can lift a poorly designed or reinforced roof off of a house.
Roof overhangs should not be more than 1.5 - 2 feet if boxed (sealed) and 8 inches if unboxed. The smaller the overhang, the less likely the roof will be lifted off the house.
Hip roofs are the best design for high winds, but are more expensive to construct.
Gable roofs are acceptable and less expensive.
The pitch of the roof should be at least 30 degrees (approximately 1 ft increase in elevation for every 2 ft in the horizontal direction).
Flat roofs should be avoided completely.
Hip Roof - Best Gable Roof - Good
Fasten rafters to the wall with metal straps (or metal plates) to secure roof to walls. For concrete block walls, the metal straps should be inserted into a concrete ring beam (which is the last row of block installed for the wall) filled with wet concrete. Allow it to dry. Fill in the space between the rafter and the concrete ring beam with concrete.
Roofs should use metal straps to fasten laths (board onto which metal roof sheets are fastened; should be at 2-foot centers) to the rafters. See diagram below. (Corrugated sheet metal is a common building material for roofs in Central America and the Carribean and is used in this design.) Sheet metal thinner than 26 gauge is too thin and should not be used.
Overlap sheet metal 6 inches to prevent leaks.
Make sure to nail the sheet metal well! Nail one nail per corrugation at the eaves and the ridge. When nailing the laths, nails should be placed at every other corrugation. Nail the ridge cap well also. Use galvanized nails with large heads if possible (or use a galvanized washer with nail).
Porches
Porches provide shade and ventiliation and are a common house feature in tropical areas. Unfortunately, porches are easily blown away in a hurricane event. To avoid house damage, construct porches as separate structures.
Shutters
Shutters protect against increased pressure inside the house (this pressure increase pushes on the roof and may cause the roof to disconnect from the house). If shudders are undesireable, use a sheet of plywood or sheet metal and bolt it to the outside of your house during a storm event. NOTE: Bolts should be fastened to the outside of the house during house construction.
Detailed Construction Information
The information and pictures in this website were compiled from the following websites.
Please refer to these websites for more detailed information and pictures:
http://www.oas.org/en/cdmp/document/codedraw/intro.htm
http://www.oas.org/en/cdmp/document/minstds/minstds.htm
Strengthen Existing Houses for Hurricanes
Make sure roof is securely fastened to walls. Install metal straps connecting rafters to exterior wall.
Check to see if metal roof is adequately nailed. Eaves and ridge need nails at every corrugation. Laths need nails at every other corrugation.
Cut eaves so that there is at most 8 inches of overhang if unboxed.
Install shutters.
Detailed Construction Information
This section of the website used information found at:
http://www.clemson.edu/special/hugo/home.htm
http://www.oas.org/en/cdmp/document/minstds/minstds.htm
Webpage by: Jen Pelto
Email: jmpelto@mtu.edu
Created: 04/01/04
Last Updated: 04/26/04