“Building it right is much cheaper than building it twice!”
Click on the links below to access questions and answers for these specific topics.
- The Florida Building Code (“our designs exceed code”)
- Screen enclosure engineering
- Materials used in screen enclosure construction
- Add-on and maintenance plan gimmicks
- Miscellaneous (why screens failed, durability, etc.)
QUESTION OF THE WEEK: “Should I remove some screen panels to prevent my enclosure from coming down in the coming hurricane (Irma)?
Answer: You should not have to…If you enclosure was designed correctly.
If you are asking this question, you’ve probably hear the lines “Remove the screens and let the wind blow through” or “It’s just like taking the sails down on a sail boat”. But remember what Sir Isaac Newton said, “For every action there is an equal and opposite reaction”.
In short, removing screen panels has a lot more affect than people realize. If you were to remove every panel, you would minimize the wind load that the frame sees, without a doubt. But who is going to do all that work and risk getting on a ladder or some rickety make-shift scaffolding to do so? So the question becomes, “Which screens and how many?”
I have seen some contractors claiming that all you have to do is remove the wall panels above the chair rail (above 3 feet). In such a case, you’ve changed the aerodynamics of the structure and may have turned the roof into an airfoil that will now generate increased lift or down force that your frame was not designed to withstand. Some engineers say you only need to remove a certain percentage of screens and magically the pressure on the remaining screens is reduced. This is most probably all guesswork since I have seen no published work that quantifies the effect of panel removal for any of the situations I’ve just described. So, if you chose to remove any panels, you are just rolling the dice.
Here is what I can tell you. Unless you have a screen enclosure designed specifically to section 2002.7 “Alternative design method for screen enclosure” of the Florida Building Code, your enclosure is supposed to be capable of upwards of 150 MPH (depending you your location) without removal of any panels. How do you know if you have such a screen? This section of code requires specific labeling on the frame regarding which panels are to be removed. If you don’t have such labeling, you don’t have one of these.
So, if your contractor is telling you that you should remove panels, he is admitting that he has no confidence in what he has built, plain and simple.
But there are further downsides to removing panel:
- Unless you have a specific removable panel system, you cannot remove the screen and expect to put it back in. Upon initial installation, the screen is stretched tight and trimmed to the very edge. Once removed, there is no margin to draw it tight again and replace the spline that holds it in place…assuming you’ve marked each panel as to location and orientation. Even then, your frame may flex and distort in the wind such that things just don’t quite line up anymore. You are going to end up replacing the screen.
- Every panel you remove will cost around $85 to $100 each to replace. That is a cost that you will bear even if the storm track shifts and completely misses you. You can easily be out $1000 or more in needless replacement costs.
- If the storm actually hits your area (and your frame survives), you will be “low man on the totem pole” when it comes to having your screen replaced. Contractors will be chasing the big ticket items, like full enclosure replacements, and repairs will only be pursued when all that work dries up.
- In addition, screen and related materials can be hard to come by after such an event. Contractors are hoarding it for their high priority jobs, every do-it-yourselfer is buying it up at Home Depot to try to fix their enclosure.
I am not going to tell anyone not to remove panels. If that is what makes them comfortable, then it is their decision. However, I believe they need to know all the risks involved.
But the bottom line is that a properly designed screen enclosure does not require such special effort…and you will never have to worry about this with a Gen-2 Screen Enclosure.
PREVIOUS QUESTION OF THE WEEK: “What is the news regarding removal or retrofit of screen enclosures in the Palm Beach county area due to faulty building permits?
Answer: Work performed by Florida Screen Builders may have been build using plans fraudulently submitted as “code compliant” to the local building department according to the Sun Sentinal (http://www.sun-sentinel.com/local/palm-beach/fl-screen-porch-problems-palm-20150318-story.html).
Florida Screen Builders is a member of the AAF or Aluminum Association of Florida. The AAF Guide to Aluminum Construction in High Wind Areas is the design manual used by many AAF members. As such, all that is required of a contractor when submitting a permit is a copy of the appropriate pages of the “Guide” as justification of the submitted design.
Such copied pages are easily modified through cut and paste either by hand or electronically, thus giving any AAF member the opportunity to falsify the original guide pages to their liking while keeping the AAF letter head.
Remember, a contractor’s prime motivation is maximizing profit margin. Falsification of design documents in only one way this may be accomplished. You need a watchdog that puts integrity of the structure first when building such a structure.
PREVIOUS QUESTION OF THE WEEK: “What is the limit on roof shape height in the Florida Building Code?”
Answer: There is no limit specified in the Florida Building Code.
Explanation: Since many contractors use the Aluminum Association of Florida Guide to Aluminum Construction in High Wind Areas to design screen enclosures instead of licensed engineers, they erroneously believe that the “Guide” is the “Code”. The limitations of the “Guide” are applicable to the “Guide” only and do not appear in the “Code”. Thus, your enclosure design can be any size and shape imaginable…as long as it is properly engineered to withstand the wind loads defined by the Florida Building Code. The best way to get the enclosure with the size, shape and look that you want is through hiring a licensed professional engineer with extensive experience designing these structures.
PREVIOUS QUESTION OF THE WEEK: “Will external add-on braces guarantee my enclosure will not fail in a hurricane?”
Answer: Probably not.
This after-thought approach has several concerns:
The braces are typically very long and slender and thus susceptible to buckling easily under compression.
The placing of such braces is critical in their effectiveness. For example, having braces only on the rear facing wall adds no lateral stability…where it is often most needed…thus the entire cage can fold over sideways. In some applications, there may be just one brace placed in the middle of the wall on each side. I have not seen how it is calculated as to how many are needed and where they are to be placed and how high up the column the upper attachment must be. I am skeptical as to any calculations that have not included a full frame computer simulation for verification.
In many cases, there may not be enough room to place these braces next to your enclosure (at the correct angle, which I would assume is 45 degrees) and stay within your property line. (I’m not so sure about anchoring them to a public sidewalk either.)
- The alternative to the above would be to place these braces inside your enclosure. This may not be possible or practical depending on the proximity of your pool or other features adjacent to the walls of your enclosure.
You’ve got to have an adequate amount of concrete to anchor into. This adds cost and complexity to the installation. This also implies that an accurate method is used to calculate the brace loads to determine just how much concrete is required. Again, anything less than full frame computer simulation-based analysis would be suspect.
These braces hanging on the outside of your frame are ugly. Even if you take them down, you still have brackets sticking out of your columns and anchor points embedded in your yard to mow around.
These braces have to be deployed either just before the storm or when you leave the house for extended periods. (This also gives the installer an out when the product doesn’t work; “The homeowner failed to deploy the system properly.”)
All of these can be avoided by having a proper design in the first place or a retrofit with the 3D, full frame computer simulation proven bracing we offer.
PREVIOUS QUESTION OF THE WEEK: “Do I need removable screens?”
Currently, according to the Florida Building Commission, your screen enclosure must be designed assuming all screens are intact during a hurricane. If someone is insisting that you need removable, retractable or replaceable screens, they are admitting that they are selling you an inferior product that they do not believe can survive the design requirement defined by the Florida Building Code.
Will removable screens improve the chances that your enclosure will survive a hurricane? Maybe. To the best of my knowledge, there has been no wind tunnel testing or other research that verifies that the change in aerodynamics from removing select screen panels is beneficial. Some engineers have even speculated that such changes might be detrimental. So, removable, retractable or replaceable screens may actually increase the chances that your enclosure will collapse in a hurricane.
One thing for sure, removable, retractable or replaceable screens will add to the cost of your screen enclosure.
To contact Steve to ask a question, send your e-mails to firstname.lastname@example.org or call (772) 486-5425. It may be chosen for the next Question of the Week.