Calculate UDL - Knocking through a load bearing wall

[Duncan.Mc]

My questions are

Do I need to calculate the Uniform Distributed Load? If NOT then why not?

How can I calculate the Uniform Distributed Load?

My Scenario is;

I would like to knock through between two rooms on the ground floor.

The wall that I would like to knock through is 4" brick (with sand cement render with a skim top coat either side).

The wall supports the first floor joists and in turn the 1st floor floor boards above which is another 4" wall of the same structure.

The opening that I would like to create will be 3m wide.

The floor area of both rooms (four on both floors) are approximately 3.6m x 3.8m EACH (measurements were taken into the alcoves)

Additional Info

Having spoken to CATNIC technical support they have confirmed my opinion that it will have to be an I-BEAM Steel, so the reason why I think I need to calculate the UDL is so that I can go to a steel supplier who can then povide me with the appropriate height and thickness of steel beam as I already have the length 3.3m and the width which is governed by the 4" (101mm) wall. I think that the beam will be unsightly if it were to protrude from the wall.

Did I also mention that I would like to factor in a provision for a loft conversion in the future. (sorry:)

I can not go to the expense of a structural engineer at the moment, which is why I am here though I will NOT undertake the job unless it is done properly and safely.

All of your questions will be answered.

All of your inputus is greatly appreciated.

Kind Regards


Duncan

[pgtek]

Hi
check with your local building inspector office they should be able to give you the size of the beam you need

cheers

pg

[Duncan.Mc]

Ive been expecting a callback from them all day today but they didnt call. Thx

[trance]

Yes, you will need to calculate not only the Uniform load, but other loads as well, for example dead load of the structure above and any live loads. You may also have some point loads.

That probably sounds like greek, but I'll try to break it down:

Uniform load is code mandated, and needs to be calculated for every part of the floor(s), attics and roofs above. For example, a floor may require 40 pounds per square foot, an attic 20 pounds per square foot and a roof an additional 20 pounds per square foot.

Dead load is the weight of the structure itself. A concrete floor will weigh more than a wood floor, but you have to consider the weight of the floor regardless.

Live load is load that varies over time. In a house, this usually means wind load and snow load. It can also mean earthquake load in earthquake zones. You can talk to your inspector to help you determine the requirements for live loads in your area.

Point loads are loads that come down at a single point (duh!!). These could be something very heavy (like a hot water heater or a large machine) or they could be a wall running perpendicular to a beam. They could also be a column bearing on a beam. These need to be calculated for each special case, and the inspector probably won't be able to help.

Once you have that, you can use it to calculate the size of the beam based on shear, moment and deflection. You have to calculate each of those three ways in order to get the correct size. I can't go into the ways of calculating those here, as we don't have time to teach an entire class in structural statics and dynamics.

Finally, you have to make sure whatever you are bearing the beam on can take the new point loads generated at each end of the beam. You don't want to break that wall or your foundation. Sometimes, adding in a beam works, but you have to install new footings to take the load.

Your span is about 9' so I think that's long enough that it'd be worth it to get some professional advice. I'd bet that a structural engineer would be cheaper than you'd think, as they are just going to visit your house, take a couple of measurements and then size the beam. Call a couple of engineers in your area and get a quote.

You are right that a 4" beam will work, but the depth would vary based on the load. You might end up with a 12" or 16" deep beam if the loads are high enough.

Another option may be a flitch beam - which is a flat sheet of steel (say 1/2" thick by 12" deep) sandwitched between two boards. These are nice because you can nail to them.