How to Prepare Sheds, Gazebos and Trellises for Extreme Winds
In this weekly Q&A column, retired builder/building inspector Cam Allen answers readers’ home renovation questions. Have a question? Enter it in the form below.
We are all seeing more extremes in our climate and can only expect it to get more intense over time. Wildfires and flooding being the two most documented this year. In every case these two extremes are amplified by high winds. One fact I was recently made aware of is that Canada ranks second behind the United States for tornadoes, particularly between April and September.
The government has been playing catchup on consumer awareness for weather extremes and they made a number of changes. The “Yellow-Orange-Red” warning alerts came into effect in November 2025. Their most recent updated website for weather alerts is here.
One notification we are seeing more often is another local warning method called “Alert Ready.” It is operated by the National Public Alerting System and has been around since 2015. These alerts only kick in when there is imminent weather with tornado capabilities or a thunderstorm accompanied by 7cm hail and/or winds at 130 km/h or more. Actually any high wind from 60 km/h can
cause varying levels of structural damage.
The internet has numerous websites listing how to prepare for extreme winds. Most are basic information which is helpful, such as store your lawn furniture, barbeque and other loose items away along with other suggestions. There are things you can do that are not always considered until the winds get over the 60 km/h. Most of the following tips are experience based, having fixed or replaced customers’ damaged homes and outbuildings.
Ground-based storage sheds are rarely properly grounded and made wind secure. Every shed should be secured with ground anchors. These heavy duty spiral earth screw-in anchors are a must. For small sheds there should be one at each corner. Larger sheds need the same corner anchors plus one every
four feet down both sides.
Secure the walls by drilling through the wall, then using braided wire rope in a loop, use a product called a cable clamp and attach the wire to the ground anchors.
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Another tip is to “skirt” the base of your shed. Wind uplift is one of the main causes of garden shed damage caused by sheds located on patio stones or frame rails. This allows a space under the shed for the wind to move it. Purchase some 2×6 or 2×8 pressure treated lumber – enough to go around your shed. Now dig a trench around the base of your garden shed about 4 to 5 inches deep. Next, fit this lumber tight against the wall of your shed and attach the lumber with proper screws. If your shed has metal walls, pre-drill a hole,
allowing the screws to slip through the wood and then attach to your shed using washers on the end of the screw to secure the wood. Backfill the soil against the pressure treated lumber and compact it as best you can, allowing a slight slope for the rain to drain away.
Other structures that can be affected by extreme winds are gazebos, carports and terraces. These structures are commonly supported on concrete tubes set in the ground with a “Yoke” fitted on top of the concrete. This is a metal bracket that will hold a 4×4 or 6×6 wood post as part of the main structure. I have also installed pressure-treated posts directly into the ground to support these garden structures.
Over time the climate and age will weaken and rot the base of the post, reducing its ability to withstand extreme wind. This is another place for long ground anchors. Using at least 30” and if you can get 36” all the better, install them right beside the wood post. Set them in the soil so they extend at least a foot out of the ground. Now drill a hole through the post aligning the anchor
end to allow a bolt to fit through the hole in the wood to the anchor.
It is often difficult to get the anchor close to the post, especially if it’s based on concrete. To allow you to tighten the bolt, fit a galvanized plumbing nipple over the bolt at the correct length so the post-nipple-anchor are all connected with the bolt and secured tight.
There are ground anchors that come with “L” brackets allowing you to use wood screws to attach to the supporting posts if you can get the anchor close to the post. If you have a metal-framed gazebo or a swing set for the kids, a couple of these kinds of ground anchors allow you to install metal pipe clamps to the L bracket. If you have a small garden trailer, parking it with 4 ground clamps, two on each side and then running a length of cable wire over the top of the trailers is effective.
My next tip is for sliding glass doors. I have been in homes during driving rain accompanied with high wind and watched the door flex in its track. While it’s not a lot, if the wind gets strong enough it will blow the door out of the track. Invest in sliding glass door locks that fit on the slider and lock into the frame at the top. Now purchase two sliding door security bars and locate one in the middle of the door and the second one at the base in the slider track. This will
significantly reduce the flex in the track and reduce any driven rain from entering. Double check that all the window locks are working properly and secured during a storm. I can remember being called to a home some years ago to replace two windows after a major thunderstorm. They were in the basement and not locked, they simply rattled around until the old wood frames failed.
Last issue is for those who don’t have a garage for their car. Recently I saw one of these hail protector quilted car covers. While I have no experience I can see where for smaller hail and branches these may work. The owner commented that it has not been through hail but a recent major wind saw small branches hit his car and it was effective.
The insurance industry seems to have picked up the ball and many now offer things like high wind checklists and guides to prepare your home for wind. It is worthwhile finding one on the internet and following it to prepare your home for extreme winds.
Images from Depositphotos
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