You will have to have an engineer spec that beam for you. You will save yourself time and money by cutting the span with a column.
250 mm x 400mm
Even using a 2x12 the spacing for 20 feet will be less than 12 inches on center. I would recommend splitting the distance with a double beam perpendicular to the joist run. This will allow you to go up to 24 inches on center. Your span will only be ten feet aproximately this way. I would double the beam. (2-2x12 joined together) Good luck. when building your beam make sure the laps on the beam are at least 6 foot apart and put a good wood glue on the 2x12s plus for added strength put 1/2 inch O.S.B. in between the 2x12 and I would also lag or bolt them together, at about 16 to 24 inches O.S.B. = Oscilating Strand Board.
Technically Yes, but you'll need to check with your building inspector because there are codes regarding structure that vary from place to place, and the inspector isn't going to pass something based on my say so.The old rule of thumb was 1 inch for 1 foot, so a 12 foot span would require a 2 x 12.A 4 x 8 isn't equal to a 2 X 16, or even 2 2 X 8's, but it should do if the load isn't too great.I'm guessing you want to go with 8" stock because you've got some headroom issues. You'd be better off structurally with an LVL (Laminated Veneer Lumber) or OSB (Oriented strand Beam) or a truss, but these are kind of pricey.If you get in trouble see if they'll let you go with them on 12" centers.
The answer to this question is too complex to describe here. There are too many factors which are not specified in the question, such as load in pounds per linear foot, spacing of the 4X12 joists, as well as grade and species of lumber.
Roof Line 30 Foot Span
You will have to have an engineer spec that beam for you. You will save yourself time and money by cutting the span with a column.
A double 2x10 beam can typically span up to 12 feet without additional support.
That really cannot be answered without looking at the entire set of plans.
A 2x10 beam span chart provides information on the maximum allowable span for a 2x10 beam based on the type of wood and the load it will support. By referring to the chart, you can determine the appropriate span for your project to ensure the beam can safely support the intended load without sagging or failing.
These calculations are not difficult, but you must know the load (including the floor weight) that will be carried. And the deflections that the appropriate building regulations allow.
2X8 set 16 inch on center.
The most accurate method to determine the maximum allowable span for a beam using a LVL beam span calculator is to input the specific details of the beam, such as the type of wood, dimensions, and load requirements, into the calculator. This will provide a precise calculation of the maximum span the beam can safely support.
Your question cannot be answered as it depends on what the beams load is... porch roof support vs a beam which will support a second story living area and a roof.
That depends on what it carries. All joist/beam manufacturers have span tables that will help you determine this.
Only if you want it to fall later.
The recommended pergola beam span for optimal structural support and durability is typically between 12 to 16 feet, depending on the material and design of the pergola. It is important to consult with a structural engineer or contractor to determine the specific beam span needed for your project.