Stair Building Ideas For Design And Construction

Lag Screws - Building Hardware

A lag screw has the head of a bolt on it, but has the threads of a screw. In the picture below, the black arrow is pointing to three lag screws that will be used to attach the angle stair tread bracket to the stair stringer.

Lag screws come in different shapes and sizes and are made from different metals.


Lag Screw Shopping Advice

If you're going to attach a galvanized stair tread bracket or other angled brackets, that are used for stair building, make sure that you purchase matching lag screws. A good example of this would be the picture above, we're using a galvanized metal stair tread bracket and galvanized lag screws.

Some metals don't work well together and if it's possible, try to find compatible bolts, nuts, screws and lag screws to make the necessary connection.


What Size Lag Screws Should I Purchase?

The best thing I could do is give you an example, using the picture above. I'm going to attach an angle bracket that had three 5/16" wide holes. I was going to install the bracket on to a 2 x 12 that was 1 1/2 inches wide so I purchased 1 1/2 inch long by 5/16" in diameter, lag screws and they worked fine.


Measuring Problems

Over the years, I have had problems measuring lag screws and bolts, when ordering them for my construction projects. It wouldn't be a bad idea to measure these bolts, before purchasing them.

Sometimes an 1 1/2 inch lag screw isn't 1 1/2 inches long. For instance the overall measurement of one type of lag screw, from the bottom tip of the screw to the top of the head of the lag screw head, is 1 1/2 inches long. There have been other times where I have measured the bottom tip of the lag screw to the bottom of the lag screw head and came up with the same measurement.

This could create a problem, especially if your measurements are incorrect, causing every one of the tips of your lag screws to stick out of the outside stair stringer.


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