The decking is two by three, with about a half-inch gap between the boards. What's the best way to prevent insect intrusion there? The crawlspace beneath is open as it is a post on pad foundation. It seems screening the underside of the joists has the potential to trap debris that falls through the cracks.
My first thought was to lay marine-grade plywood over the decking, but given the potential for water to enter through the screen and lay on the floor, I'm a bit leery. But, since it's open year-round, will the airflow be enough to dry wet spots?
Your thoughts appreciated.
-- K.T., Lakeshore Heights
ANSWER -- I agree with you that tacking screen to the underside of the deck joists may cause you nothing but headaches with the accumulation of debris. Unfortunately, installation of plywood or other flooring above the existing decking may cause equal problems with moisture accumulation and rot. There may be another way to approach this issue, and I will elaborate on that topic and other difficulties you may run into in your project of screening in your existing deck.
This summer has been a particularly bad one, in relation to mosquito infestation, in several cottage areas due to the large amount of rain received. Your desire to screen in your existing porch, to maintain your sanity when attempting to sit outside, is a common one. The fact that the roof of your existing cottage overhangs this area is a distinct advantage, which may allow you to build the walls and install the screens with minimal difficulty. The problem of how to completely stop the little vampires from entering the newly created screen porch from below can be troublesome.
Most homeowners would simply choose the path of least resistance, sealing the decking with solid floor coverings, and I commend you for your search for a better solution. Covering the existing, well spaced deck boards with anything other than unsightly pressure treated plywood may trap rain and snow, allowing the older decking to rot prematurely. Even this specially treated plywood would require several holes drilled to allow drainage, which may partially defeat the bug-proofing. I agree with you that leaving the existing decking exposed will allow for maximum drying, and lead to a very long life expectancy due to the overhanging roof.
With many unusual retro-fit renovations, like the one you are attempting, a bit of open minded creativity is often required to find solutions to difficult problems. In your case, ignoring the decking completely may be the best approach to stopping pesky 'skeeters' from entering your newly screened porch. I would recommend an attempt to prevent any bugs from gaining entrance to the entire area under the deck of the newly enclosed space, rather than just the deck, itself. Installation of screening around the perimeter of the open crawlspace may also prevent unwanted other insects, such as bees and wasps, from taking up residence where they are not welcome. Having been stung several times on the legs last weekend at my own cottage by wasps living under the steps of my deck, I would strongly advocate this approach. The difficulty in this method is to secure the screen effectively, without it being subject to damage.
I will suggest two possible methods to keep kids and other critters from tearing gaping holes in the vertical screens that you will be installing under the existing deck. The first, and most simple material available to support the screening, is pre-made lattice. This easy to install material is available in various shapes and sizes in either natural or treated wood or plastic. Depending on the height of your deck, lattice of one to four foot widths could be purchased and nailed to the existing support posts. If the posts are too widely spaced, or not in the proper locations, installing a simple wood skirting frame nailed to the underside of the deck would be required. The lattice could then be nailed to this frame, followed by the screen, which should extend right to grade to prevent pest intrusion. Using aluminum screen material, rather than fibreglass or other more flexible screening, may further resist damage.
Unfortunately, many home and cottage owners do not like the look of common lattice, and a more elaborate method of skirting in the bottom of the screen porch may satisfy those aesthetic concerns. Having built many decks in my time, I prefer the look of horizontal one by six boards, spaced similar to your decking, nailed one above the other to the skirting frame below the deck. This will not only give sturdier support to the bug screen, it will also allow for easier installation of an access hatch or gate below the deck. This last component is an important one to allow removal of any debris that builds up under the screen porch and to allow for any future repairs or levelling of your new bug sanctuary. Also, this newly enclosed space may provide an excellent storage space for outdoor furniture, lawnmowers, or other garden tools.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the President of the Canadian Association of Home & Property Inspectors - Manitoba (www.cahpi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.