Calculate the support requirements for a load bearing wall -

Question

I am in the process of removing a load bearing wall to open up the kitchen to the dining room. The house was built in the 1700 in the Cornwall(south England) and is constructed from stone using lime and sand mortar. It is a 2 story house.

I have removed the lath and plaster for the wall that I plan to remove(fig 1). The wall span it will need to support to is 2.4 meters. The supporting wall being removed is on the ground, so the beam needs to support the weight of the second floor. The room dimensions are 2.5m by 3.5 on the kitchen side of the wall and 4.5 by 3.5 on the dining room side of the wall. So I assume the total area the beam needs to support 4.5 X 3.5 + 2.5 X 3.5?

There is a brick wall on side that the beam(fig 2) can rest on. On the other side there is nothing but it does appear to have some concrete foundations(fig 3).

My question is how do I calculate the size of metal I beam or, ideally, oak beam that is needed and are the footings (image below) strong enough to support a vertical beam or do I need to remove them and build new one. Lastly what size/strength of vertical beam do I need to support the weight?

Fig 1 Fig 2 Fig 3

Answer 1

You have several issues: 1) new beam size, 2) adequate connections to the footings, 3) lateral loads, 4) footing size

1. I’m am American so I don’t know anything about meters, but I’ll try. It appears you want a 2.4m opening (about 8’).

You have one upper floor plus a roof system resting on this wall (header). So the kitchen side has 2.5m (7’) floor joists spanning the kitchen plus on the Dining Room side you have 3.5m (about 10’) upper floor spanning the Dining Room for a total of 6m (about 19.6’). However half will rest on other walls (not the header). Floor loads are 40 lbs. per square foot by U.S. codes. So 40 psf x 19.6’ /2 = 392 lbs. Live Load per linear foot plus Dead Load of 10 lbs. per square foot = 10 x 19.6/2 = 98 plf for a total load of 490 plf.

I’m going to assume the roof is framed similar to the floor. So, roof loads are about 25 psf live loads (snow loads) plus 15 psf for dead loads. Therefore you have about 40 psf roof load.

Floor load = 490 plf, plus

Roof load = 392 plf

Total load = 882 plf on your new beam.

You’ll need something metrically equivalent to a 4x10.

2. I’d use steel connectors between the beam and 4x4 post.

3. The existing wall has some lateral bracing, so I’d cover the remaining wall with 1/2” plywood so it doesn’t move laterally.

4. The upper floor and roof are NOT distributed uniformly along the wall and then to the footing anymore. Therefore you’ll need a footing that can support 882 plf x 8’ / 2 = 3,528 lbs. at each end, which doesn’t seem unreasonable and you may be able to reuse your existing footings, but you’ll need it designed.

Note: I’d like to call everyone’s attention to the header’s connection to the “king stud” on right side of the existing opening. We’ve come along way in framing.

Answer 2

There is unfortunately no way of calculating this unless given blueprints of the house. Even if we did calculate it and even we overdid it, for something this big no inspector will pass it without an architect stamp.

I can mention two things before you start this...

• given the current construction I don't think the beam will be a big deal.
• you will almost surely will have to have new footings created. You will be made to dump a bunch of concrete on both sides and this could potentially be a much bigger deal than the header. (I get that the current footings worked for 300 years but they probably won't pass code for new work)

(also jealous because they stopped selling that fajita kit near me)