Open plan design/cost of steel beams

[Bingbangbingbangbong]

So this may be a ‘how long is a piece of string’ question, but here goes!

I wondered if anyone had some experience of creating an open plan living space and had a benchmark for how much the cost of load bearing steel beams were?

We are currently mulling over our house renovation and are stuck on how to proceed with the living/kitchen area.

I have attached our current floor plan to highlight the issue - to the back of the property was a living room and the previous owner added an extension to have a dining room too. We have replaced the dining room with a kitchen, but find that the way the space is configured with the halfway walls in-between means we don’t really have enough space in either the kitchen or living room layout.

We plan to put a further 2 meter extension on the end of the (Previously dining room) kitchen to make more space, but I wonder if it would be a better plan to also take down the two half walls inbetween and create one large space overall?

My cousin is a structural engineer and said the cost of steel would be so ridiculously high, it wouldn’t be worth doing. But then we have had builders who say the opposite. To be fair, my Cousin does have a tendency to be very dismissive and refuses to even draw up a plan of the open area so we can even take it to a builder to ask (he is doing the plans for free, so we certainly can’t force him to do so).

He may well be right, but without a plan, I can’t really find out for sure!! He said it would need to be a full rectangular steel structure needed to replace the two half walls. Has anyone done anything similar or managed to amend a similar floor plan?

Thanks all!

So how long does the steel need to be? We had a 2m one a few years ago and it was about £2k I think. There was a bit of extra cost for a machine to manoeuvre it into place but nothing awful.
Another thing to consider would be a weight bearing pillar somewhere.

Having re read, the steel would be 2.7m? That doesn’t seem out of the question.

@GreyishDays

As to how long the steel needs to be - from what my cousin says, it would need to be across the entire room if we remove the two half walls, so 5.7 meters at minimum. Possibly a lot more if it needs to be the full rectangular steel frame needed instead.

My entire upstairs is supported on a single steel beam across an existing substantial stone built building. It's about 6m. (It had to go diagonally because of where the windows are.) Not sure that it cost 2k but that was 20 years ago. My builder went off for a week at Christmas before it was in place. My brother was up visiting. We were bored.

Getting it up and into place wasn't that difficult. My brother and I - neither of us big blokes by any means - and a couple of friends (who helped with the final heave) got it up into position with a little ingenuity and levers. We certainly didn't have to get any kind of crane in. The builder shit bricks when he came back but was somewhat less freaked out when he'd checked everything and found were were only two mil out of level - well within the tolerances.

In my experience the people who actually do the job are the best at telling you how to do it. Architects and Structural Engineers live in some kind of strange, abstract universe and work with ideals. Ask the blokes who get their hands dirty and actually turn nice neat fantasy drawings into real-world bricks and mortar.

OP. Sorry but with the diagrams it is impossible to say really. You would need a structural engineer to assess it, although a builder should have a rough idea.

The steels in isolation are not massively expensive, it is putting them in place and also associated structural work that is required. For example, we had a large extension done with a circa 9m steel put in place to hold up the rear of house for a then wider extension. However, it wasn't as simple as that. Whilst there are calculators that you can use online, the bigger issue is the structure it sits on.

For example, for our steel, we have two that weigh total of 1.5 tonnes. To support that, you cannot put such weighty steels on the existing wall structure as the foundations much be able to support in such a small space, the weight of the steel plus the back of the house. So our house had to be totally propped up, specialist jacks hired to raise the steel into place. The parts of the wall holding up the house, part of it had to be demolished, and then the foundations drilled out and replaced with steel reinforced concrete foundations and then wall then rebuilt with special load bearing blocks. It was a substantial piece of work but having seen it, the chances of them sinking must be close to nil.

Our builder reckoned the structural engineer had over egged it, but I would rather be safe. For example many steels are out in place with a 10cm overlap, our have 50 cm.

I would speak to a builder you trust, but in reality unless they have drawings and a spec it is tricky to price. I found that architects were a lot closer to the actual cost

I had a ground floor fireplace wall removed, about 4m. As I didn't want to take the fireplace on the floor above out we had to put two parallel beams plus upright beams either end and to support those cement plates (or whatever they are called) below floor level. It was expensive but not astronomical. Just get someone to cost it out.

support those cement plates (or whatever they are called)

Hearths or hearthstones.

Won't know until you get the plans and cost it!

I’d say it’s well worth the time and effort
Little big house is also worth a look and read, as she explains flow in a house and also how to frame