Hi all,

I have a question regarding joist notching and strength. See the attached diagram for an idea of what I'm talking about!

There are about 5 joists in my upstairs floor that are supported at one end by the external wall and at the other end by a beam running perpendicular (joists a-e, beam A-B). This beam bridges the gap between two internal solid walls which the other joists all rest on. The beam runs along the top of the stairs, approx. 8 ft in length.

I have noticed that the joists in question are supported by the beam by means of notches cut into both the joist and the beam. The joists have the bottom half (yes, half!) cut away and the beam has the top half cut away, so that the top and bottom of beam and joist are flush. See the attached photo. My question is: is it acceptable to have notches like this that are half of the joist/beam depth? I've noticed that the floor has a couple of millimetres movement in it when I walk on it, could this be caused by the joist/beam arrangement?

The house is approx. 25 years old with no damage to the ceiling below, but the movement does cause a bit of squeaking in the chipboard floors which is pretty annoying!

Any help is much appreciated!

Oops, the pictures didn't upload first time! Here they are...

Hi Aldo

If the joists that are cut is not resting on a bearing wall, the joists are rated at the width that remains and can split from cut inward.

Chuck

Thanks Chuck, but what exactly do you mean by "joists are rated at the width that remains"?

Since the house has stood up for 25 years and there are no signs of any splits in the joists I'm assuming they're not going to fall down now. But could this cause the flexing in the floor when I walk on it?

Hi Aldo

If u have a 2x8 and notch out 4" on the bottom and use the remaining as the support, u have made the holding power a 2x4.

This can make your floor spongy and flex in that area.

Chuck