|The guest villa roof is going up!|
Mary Ann's Tropical Building Page
November 9, 1997
Since our Oct 9, 1997 report about building on a Caribbean island, we have
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Designing the perfect roof in Anguilla is a frustrating process. Cost is always one factor to consider. Galvaluminum sheets are very inexpensive, but most of those roofs blew away in Hurricane Luis. Many people in Anguilla will only consider a concrete roof for hurricane protection. But a concrete roof acts as a heat sink, sucking up energy all day, then slowly radiating it all night. And concrete roofs often leak. If you see rusty leak stains, the rebar is rusting away and eventually you have a slab of unsupported concrete over your head waiting for an earthquake to dislodge it.
For the guest villa we attempted to consider all factors (except perhaps low cost!) It has concrete on top for strength, a white elastic coating for waterproofing and to reflect the sun, an steel mesh panel with foam for insulation and strength, a radiant barrier to keep out 99% of the sun's radiant energy, and then wood ceiling and rafters for looks and better acoustics than concrete.
That about covers everything possible. Well actually, we had thought about two more layers: batterns and shakes over the concrete. But this was too much even for us. The one factor that this roof does not address adequately is cost. Since it is such a small roof, we decided to try it and see how we liked it.
|Cover rafters with T-1-11 plywood.|
|The trey roof has exposed rafters.|
Radiant barrier is a very efficient method to combat heat from the sun. A tiny layer of shiny metal foil can reflect 90% of the suns energy. If you cannot give it a 2" air gab to resist convective heat, then it loses 30% of its effectiveness, but it still works. In this roof design the radiant barrier is on the top side of the plywood, facing the underside of the 3D panel. Since the underside will not have concrete, we have the air space needed to maintain maximum efficiency.
There is a myth that
Dust Accumulation reduces the value of radiant barrier.
But a study from the Tennessee Valley Authority indicates
that dust accumulation had very little effect on the effectiveness
of the radiant barrier.
|A ring beem is poured around the edge.|
On the top of each wall the rebar is still sticking up. This will be bent at an angle to match the roof line and tied into a layer of 3D panels, which will form the outer roof. The 3D panel construction was discussed in an earlier report.
The foam in the wall panels was partially burned out, then
concrete was poured to tie all the steel bars into a
unit. Then the remaining foam on the inside of the walls
was burned out. When the roof panels are tied in place,
this inner trough will also be filled with concrete to
complete the ring beam.
|Wooden roof awaits radiant barrier and Insteel panels.|
The guest villa has a verandah all the way around. It is built of wood. The supports are 6x6 posts, tied into the foundation with Simpson hurricane saddles. The cross pieces are 3X8s, glued and bolted.
A 3x8 header is bolted to the outer wall to take the eventual rafters. The bolts were tied into the Insteel panels before they were sprayed with concrete.
Our goal was to open accounts with dependable suppliers who would take an order over the telephone and and deliver to the dock. We haven't been that satisfied with shipping from San Juan and St Martin and in Anguilla, essential items are often "finished" (i.e., last week there wasn't any 1/2 inch PVC pipe on the island and last summer all construction stopped because the island ran out of cement).
The shopping wasn't as good as we had hoped, but we did find severalsources.
For example, we bought 1000 Mexican tile and 60' of trim tile from MSI, a lumber yard. They delivered it to the inter-island freighter, the Karma, before the Wednesday 3pm cut off. The goods arrived safely in Anguilla on Friday afternoon.
We were able to get a complete computer catalog of MSI's stock
and prices, and
MSI has email at
firstname.lastname@example.org. The MSI
Tile and Bath store has a web page at
MSI has recently purchased Sea Chest next door, which is
a ACE hardware outlet, so you can purchase hardware items through
them as well (fasteners, paint, etc.). Telephone: 340-776-8800.
Of course, we failed to inspect the actual terra cotta tiles in the warehouse and what arrived was the standard sharp-edged style instead of the pillowed-edge style we were expecting. Sigh....
|Fence posts and wire mesh, with concrete runoff gutter.|
The property is now fenced with wallabee wood posts and wire goat mesh. The posts are dropped into "holes of opportunity" (any small cracks or crevices we could find in the solid rock). Any openings under the wire are filled in with rocks to keep the goats out. The roadside gate is still under design.
Along the steepest part of the propert where we get storm runoff from the dirt road, we have built a drainage concrete culvert into the fence and directed the water to a pipe. From there we will dig another deep hole for a palm tree and direct the water into it.
We have created a pathway from the beach to the gazebo and planted it with a mossy kind of grass that grows into mats and doesn't need mowing very often, nor do you have to water it once it is established. The grass bunches up and expands as it grows. Apparently the grass doesn't produce seeds--it is propogated by root division. You don't want it too near the house of cisterns because it is very invasive.
The idea is that by the time you have walked to the house you will have cleaned the sand off your feet on the cushy grass.
|Camouflage paint for a large retaining wall.|
On the eastern boundary of our lot, near the road, there is a tall concrete block retaining wall for a neighboring driveway. In order to hide it, we created rock planters along the edge and plan a hedge of oleanders. Goats won't eat them because they are poisonous.
What to do until the hedge grows up?
We are painting the wall in jungle camouflage green to blend into the foliage. Delphine at Richardson Paints in North Hill has been very patient and helpful in mixing the colors.
We hired Nowell Rogers, the Chief Engineer of Anguilla, to go over our office plans and ensure that a post would not be needed. He came up with an embedded beam in the second story floor. This means you have a lot of extra steel in one area, but it doesn't stick down into the room below - it is embedded in the thickness of the floor.