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What Are Notching & Boring Joists? (Complete Guide)

Notching & boring is a part of plumbing work, and you should know them in detail, which will help you enhance your skills. If you want to work with wood and lumber, you should know how much you can create holes & how you may fill that.

Apart from that, notching & boring will also help you to make a perfect joist. Today, we will go through these two terms and show you how you can create nothing & boring in your lumber or plywood.

What are notching & boring joists?

A notching joist means to create holes or notch to join a particular timber or wood material with the other. The boring joist means filling those holes or notches with the other notches or something else. There are some rules for creating notching & boring joists according to the preset standards.

Notching is the most crucial part of plumbing, woodcutters, and those who create holes & notches in joists because a silly mistake of making a wrong notching might damage the entire joist.

When you create a notch on your joist, you should never cut more than ⅓ of your joist depth. Otherwise, the joist will be broken, and you cannot use that part.

Apart from that, the boring joist is something special that you use to attach two joists or use those holes to fill up with something else.

Maybe your notch will be covered with metal or screws that will attach two different joists. If you create a perfect notch on your joists, you can bore the holes or notches with anything.

If you notice your plumber or woodcutter, they use codes and follow some common standards while cutting your wood or metal objects. If you want to have that experience, you should keep these codes in your mind to avoid making any mistakes.

However, your joist quality will also play a crucial role here since the quality of wood will ensure a secure notching & boring.

If you don’t know how to create notches on your joist, you should go through the given codes where it will be shown that one-third of your joist should be cut to create a perfect notch. Only then you can expect to bore it with anything else and fill the cut area.

You can design your joist with something else that would be a perfect solution for creating a joist or angle.

Notching joists:

Notching joists is not easy since you need to use your experience and cut the joist approximately one-third to get the safest notch.

When you break this rule, you will find it challenging to bore it and create a perfect joist accordingly. If you don’t make a notch in your joist, you will fail to create any angle and will fail to attach with other joists.

You may use some plumbing tools and a measurement scale to determine the joist’s depth and cut one-third of it.

It’s the standard of creating holes or notches in your joist. If you are not sure how to notch professionally, you should hire a plumber or woodcutter, and they will give you precisely what you want.

Boring joists:

You create holes by notching a joist; it’s time to bore them with another joist or screws.

If you use a particular joist for angling, you must create some notches on it to attach with another joist, and it will be easier to use regular screws to attach them. Before that, you must bore the two different joists together to avoid any mistake in screwing.

Once you have done a boring joist, you will create a perfect angle to use in different places.

If it is not, then there must be some wrong notches on your joists. Sometimes, the joists will be so weak that you cannot make notches and will fail to bore them accordingly. Before boring any joist, you must ensure that your nitches are perfect.

What are the codes for notching and boring joists?

In general, notches should be avoided in the middle third of the joist, where the bending pressures are the greatest.

Additional regulations that must be followed to be by the International Residential Code (IRC R502.8 and R802.7) are as follows:

You are not allowed to drill any holes with a diameter greater than one-third of the depth of a joist. There should not be any holes within a two-inch radius of either the top or bottom edge. No holes or notches may be located closer than two inches to one another.

In terms of depth, it is highly expected that notches shouldn’t be in the center third of the joist. However, holes can be drilled here.

No notches should be more profound than one-sixth of the joist depth. It is recommended that the length of a notch not exceed one-third of the total joist depth. Cracks are more likely to appear after square cuts.

Except for the very ends, massive beams (those with a thickness larger than 4 inches) are not authorized to have notches cut into their tops.

What is the maximum hole size in joists?

The maximum hole size in the joist is ⅓ of the joist depth, which means if your joist is 2×12, the maximum hole size would be around 3-¾ inches. If you cut more than that maximum size, the joist will weaken, and you will get a weak joist angle from that timber.

You can use different sizes of a joist, but the process of boiling it will be similar to that of the other joist. You can create less than one-third of your joist to make a certain angle.

You should use a sign on your joist that you will cut that particular area and will stop your cutting machine at that point. Otherwise, it will be a serious problem.

Since 2×12 is the most used joist on every house, I asked to stop creating holes more than 3-¾ inches deep.

Creating a similar hole will give you the best support, and you will love that angle. However, you should calculate the joist size to find one-third of its depth to create safe notches.

Where should you not drill holes in joists?

You should not drill holes in your I-joists bottom or top flange since these areas are very sensitive and creating holes or notches might be dangerous.

In most cases, plumber and carpenter don’t put their cutter on the top & bottom line of any joist to avoid making a mistake. They create holes in the middle or at the corner of the joist.

If you mistake creating niches at the bottom or top of your joist, the boring joist will fail to stick to that notch perfectly.

Creating holes in those areas might sometimes break your joist and make it useless. Therefore, you must always look for the strong part of your joist to create holes and notches.

When you drill your joist, it will put some pressure on the wood to make it evenly. If you drill at the top or bottom of your joist, it might break or damage those areas that you cannot even recover by any means. Therefore, avoid drilling holes in the top & bottom areas of your joists.

4 things to consider while notching and boring joists

Here are 4 of the things you must consider while notching and boring joists; otherwise, you may damage the joist, and will make some errors in notching & boring. Let’s see what those factors are that you cannot avoid.

Size of the Joists:

Before beginning work, ensure that the joist size is appropriate for the span.


Notches can be cut into the top OR bottom of the joists, but not both, as long as they are formed within the permissible region and do not exceed 35 millimeters in depth.

Location of Holes:

Holes may only be drilled on the joist’s centerline within the allowed region to a maximum diameter of 65 millimeters (mm). Additional holes must have a minimum distance between them of at least three diameters (center to center).


Beams, rafters, purlins, and binders made of single or multiple timbers must never have their notches or drill holes drilled without first doing the necessary calculations to justify the remaining timber.

Keep in mind that this advice does not apply to engineered joists such as JJI joists; instead, a reference should be made to the instructions provided by the manufacturer of the specific product in question.

Final Thoughts

A notching joist refers to creating holes or notches on the joist; on the other hand, a boring joist means to add another joist or fill up those holes or notches to create L-shape or any particular angle. But your boring joist will entirely depend on creating some perfect notches on that joist.