Using Shims to Level the Deck Surface

It is likely that you will need to make some adjustments in order to give the appearance of an even deck surface, given that the majority of deck frames are not completely level and often we tend to go overboard in our deck designs. Because the size of the joists can change from board to board, it is possible that you will need to add wood shims in order to increase the position of the decking over low joists. When you have high joists, it's possible that you'll need to plane down the surface height of the joist so that it can allow a level floor height. Because the decking helps to bind the frame together, it should be able to assist in rectifying the majority of differences that exist from joist to joist. The weight of the frame and the gravitational forces should rectify the majority of the minor errors.

Deck joists that support 1 12" (38mm) or 5/4" (32mm) dimensional wood decking do not need to be planed. PVC or composite decking will show up waves between the deck's joists. This means that uneven joists will need to be installed with more care and plained down.


How much plaining needs to be done will depend on the type of decking and how it is joined. Different decking materials show how the height of the joists changes in different ways. The worst kind of decking is made of plastic. Most composite decking openings are 1" (25mm) thick or less, and the material is also very flexible. As the deck warms up, the deflection gets bigger. On a hot day, PVC decking can sag between the joists and make a small wave.


Read more: Squaring the Deck Frame


Since wood is more rigid, the joists won't need to be planed. Because the decking is rigid, the height differences between the joists can be kept to a minimum. As the height of the joists changed, the decking rose and fell slowly, adjusting to the change. Making it so that you can't tell the difference between the joists from the ground.


The main reason to plane deck joists is to make height differences stand out. If not, you don't need to plain the joists. If you can see changes in the joists, it needs to be fixed. There are a number of good ways to build that will help keep the differences between joists to a minimum. The amount of joist plaining that needs to be done will be cut down by the following five building methods.


After finding the joists that need to be plained, you can next choose to level out the joist using one of the following three methods: a wood planer, a belt sander, or a circular saw. The concept is straightforward: delete the material that is located over the line. Simply reseal the decking surface with an end treatment, and you will have a surface that is consistent.


The use of a wood planer, whether powered or manually operated, is the method that is both the most efficient and successful in levelling a high point on a joist. Simply scape in a back-and-forth motion until the joist is at the same level as the level line. The high material on the joist can also be planed down using a belt sander, which is another option. Comparable to a wood planer, with the primary difference being that this device grinds away at the wood rather than chopping it off. Use sandpaper with a low grain, such as 60 grit, which is typically used to remove old varnish off hardwood flooring. Something that can really chew into the material and get rid of it. Sanding off the high material requires taking your time, applying a modest amount of pressure, and moving the sander back and forth. It will take a little bit more time than using a planer, but it will still be quite effective, and it has the added benefit of removing material in smaller layers, which provides you with a higher level of control.

Cutting the material for the upper joists with a circular saw. This is risky and difficult to do since a circular saw should ideally have more than a quarter of an inch (six millimeters) of material to hold the blade while it is cutting. When installing deck joists, refer to suggestion number one if you have a crown differential that is greater than one quarter inch. To plane the joist so that it is even with the other joist, begin by gently holding back the guard and starting with the blade sitting on top of the joist. Cut carefully just above the line. Move carefully because, as I mentioned before, the blade should ideally have some material above it to guide it and will quickly stray from its intended path.


As a framer, I learnt in a manner that was considerably more rough and risky. Adjust the saw blade to a depth of 1/8 inch (3 mm), then pull the saw across the joist in a direction that is perpendicular to the joist. The high material is chiseled away as the blade glides and rotates over the joist. Although the cut will not be ideal and it will be difficult to remove material consistently over the line, it is not impossible to do so. Although it is not encouraged, doing so could be an option in a pinch.

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