|BigWallop wrote: | |> The point about there being "three floor beams", which I take to mean |> joists, means to me that this isn't going to be a small opening. That's |> unless the joists are very close together, which then also means the floor |> above is taking a bit more than normal loading. | |Three beams to me suggests a gap of 800mm c/c at normal joist spacing. |About the width of a normal door frame.
Actually the beams at this point are 410 on centre, but the 3rd one (where there will be no supporting wall), is only 220mm as this is where the staircase restricts the width.
| |> If the joists for the floor above are all resting on this original wall, it |> surely means that this wall is a main supporting wall in some way. To |> remove even small parts of it, which, by the description given, sounds to be |> of a solid masonry construction, and replace with a simple timber door |> frame, isn't something to be taken lightly. A simple timber door frame |> isn't strong enough to take the place of main joist supporting masonry in no |> way, and the OP may need more substantial timbers, or even steel, to take |> the place on the original brickwork. | |A stud wall can be load bearing, there is nothing mystical about a |single course of bricks. You might be supprised by just how strong a |timber frame can be, especially under compression.
Hmmm, yes. This is why I was wondering if I could incorporate some load-bearing into the door frame, -possibly supporting a (then only semi)-cantelevered beam across the top of the existing brick wall. | |A few back of envelope calcs should give you a feel for it. Say the |floor joists above were 4m in length. Ordinary bedroom say, with a |typical loading of 0.8kN / m. That will give you a down force of 1.6kN |at the wall for each joist. Multiply by three since there are three of |them, giving a total load of 4.8kN or approx the same as supporting 480kg.
Again, this is almost exactly how it is laid out. how did you know? !!! | |That give two questions, how strong does the crossmemeber need to be at |the top to pickup the load of the middle floor joist at the centre of |its span, and how strong do the sides of the door frame need to be to |take the total load in compression. | |A fiddle with superbeam shows that a crossmember of 100x100 (i.e. a |couple of 4x2"s side by side) will exhibit a total deflection of under |1mm and well inside the limits on shear stress. Assume the vertical |posts are 2.4m long, use a pair of 4x2"s for each side, sharing half the |4.8kN load each. You get compressive stress of 0.24 N/sq mm where the |maximum permitted for bog standard c16 timber would be 3.33, so again |loads of margin, and that is before you put in the door lining and any |other noggins.
That's helpful. Thanks. (I must have a look at Superbeam. Never tried it before). | |> I'll stand by my first reply of advising a structural engineer giving proper |> advice on this one. | |Nothing wrong with that bit of advice, although I also expect with a |little research you could do it yourself. It would get more complex if |the floor above was picking up other loads (like load bearing walls), |but only carfully looking at the structure and layout will answer that.
All other walls on the above floor are stud, and do not rest on any of the three beams in question.
John, may I thank you for a really helpful, comprehensive reply.
Regards, Howard.