Can you notch a pergola beam? By how much?

[coley3]

I have installed posts for a free-standing pergola underneath the existing house gutter.
To give me more height on my pergola roof, can I notch the beam to fit under the gutter?

Post - Merbau 90 x 90

Beam - Structural pine 240 x 45 x 4200

Please see picture.

 

[MitchellMc]

Hi @coley3,

You can physically notch a beam, but doing so will significantly reduce its load-carrying capacity and the length it can span unsupported. When you notch a beam, the remaining depth of the beam becomes the effective size for structural calculations. For example, if you were to notch out half the height of your 240 x 45mm beam, it would essentially function as a 120 x 45mm beam in terms of strength and span capacity.

Given that your beam is 4.2m long and it is running this length unsupported, notching it would not be advisable. A 240 x 45mm structural pine beam is likely already close to its maximum span limit, even without any notching. Reducing its depth further would compromise its ability to safely carry loads, especially if the pergola will support roofing or additional weight.

If maintaining height under the gutter is important, you may need to explore alternative solutions, such as raising the gutter, using a smaller beam with additional intermediate supports, or consulting with a structural engineer or builder to determine the safest approach. Alternatively, there are these Roof Extenda MKII Bracket With Black Weather Seal Package which are for mounting beams up above the roof line.

Please let me know if you have any questions.

Mitchell

[coley3]

Thanks Mitchell - good advice.

[Noyade]

Made by a builder of 50 years experience, 35 years ago - but would they be acceptable today?

Fabricated brackets...