How to make and fit DOUBLE LUMBER GATES and how to offset and align the hinges
allowing the gates to open over raised ground.
Page one: Introduction and How to hinge and align a gate
It's a simple enough task to build and fit a standard type garden gate as long as the posts are parallel and the ground is level and even, but what if this is not the case? What if the ground slopes up from the gateway entrance? How can you open a gate if the ground slopes up higher than the bottom of the gate?
Well, there are a few ways to counter this problem, but they might not be suitable in all cases.
Here are a few of the more common solutions:
1. You could fit the gate to open away from the slope, but depending on the make-up and position of the fence and gate, this might not always be possible.
2. You could raise the gate higher off the ground so it can open over the sloping ground. But that's not much good if you are trying to keep little puppies or other critters locked in. They would all scarper under the bottom of the gate.
3. You could dig out the ground that slopes higher that the bottom of the gate. Not always possible.
4. You could fit a sliding gate. Mmmmmmmmmm, that's a bit tricky and really needs a complete chapter to go there.
Or you could offset the hinges.
Offset the hinges. That is, align the hinges so that the bottom hinge is not in a vertical line (directly under) the top hinge. The amount of offset determines what the angle or pitch of the gate will be, when opened. When the gate is open, the bottom of the gate angles up, thus enabling the gate to open over raised ground.
We were recently asked to make and fit a gate into an opening in an existing lumber 1800mm (6ft) high fence. The opening was over 2100mm (7ft) wide and in this case double gates would be more practical that one wider gate. The gates had to open inwards and had to be low enough to the ground to keep a little puppy in. The ground sloped up inwards from the gate entrance at right angles to the fence line, as well as sloping along the fence line. We were told that we could not dig out any of the ground that sloped upwards.
Below (Fig.1) is a drawing of how the bottom hinge on the gate can be offset to enable the gate to open over raised ground. The red line in the drawing shows how the top and bottom hinges should be aligned.
How much should the bottom hinge be offset?
About half the degree off plumb, of the degree off level that the incline of the ground is along the fence line. Lost yet?
Okay! Suppose the upward slope of the ground along the fence line is 6 degrees (approximately a rise of 1 in 10), then the bottom hinge should be offset vertically from the top hinge by 3 degrees.
Of course you can always work it out by trial and error, have a couple of people hold the gate in open position and measure the offset.
NOTE: Sometimes the ground might also be sloping up at right angles to the fence line at a steeper angle than the slope along the fence line. In that case, the bottom hinge will also need to be offset at right angles to the gate. This can be done by adding a block of wood to the gate and fence thus packing the hinge out. You will see how this is done in the following pages.
The drawing below (Fig.2) shows how the gate tilts up when opened.