Structural engineer or builder...?

[Minstrelle]

We're looking to knock down the remnants of a wall between our lounge and dining room. I think that someone before us, knocked about 3/5 of the wall down anyway, leaving a square arch, with architrave around it, and no door.

To give you an idea, the wall is about 3m long in total and normal height, of which about 1.75m has been removed in the middle, leaving about 60cm one side and just under a metre the other. With about 60cm above the "frame" to the ceiling. The approx. 1m side goes into the outside of the house. Hope that makes sense.

We/I would like to get the rest removed, in order to make the rooms into 1 and be less divisive. The upstairs bedroom dividing wall is almost definitely above, or nearly above it. So I think I would need an RSJ in to support the wall, or similar.

We had a builder out for something else, who said that's what we would need. He also said that, depending on where the joists were, the RSJ would "hang down" about 6 inches into the room (which would obviously be plastered over) and that, because the wall went into an outside wall, there would also be 4-5 inches of wall left at the end. However, do I just take his word for it, or should I pay a structural engineer (or someone else) to come out and have a look? If so, does anyone have an idea of cost - we're based in Surrey. Any thoughts/comments?

Few qs

1. Is the wall above a solid brickwall or studwall?
2. Does the first floor floor joist sits on this wall? this goes back to the q your builder asked - depending on the orientation of joists.
3. Is there a 2nd floor? if so, does it also sit on 1st floor wall?

These are the qs a structural engineer will answer for you then advise you the size of RSJ required or not even required. Your builder could be taking a guess and picking the same size of RSj as his previous job. Saying that, since the width of opening is only around 3m, he may select a slightly stronger RSJ off the shelf to be on the safe side. Still, better to spend 200 to call out a engineer to confirm.

Thanks hong - re the wall above - brick. Not sure about the joists - do you mean is there a joist that runs 'along' the length of the wall to be removed - or do you mean whether the joists go over the top of the wall to be removed, and are perpendicular? There is no second floor (only an attic).

I guess it is better to be safe than sorry, and I don't want the floor/ceiling collapsing. And £200 isn't as bad as I thought in terms of price - just got to find one now. Everyone I've googled seems to be commercial-based.

if its Brick then you can't just lay timber joist under to support (well better not). A RSJ is preferred

Floor joist - if it runs into the wall then the wall below is load-bearing, meaning more load = bigger RSJ needed. If runs in parallel, then the RSJ will only support the brick wall above, then may not need a engineer involved.

Yea, engineer can visit and check above then off to design a RSJ only if needed. Shouldn't take more than 3 hours of his charging time.

Similar to what we have just done, the Engineer came round and had a look and advised extra timber for us, and it cost £150 with no drawings or calculations required

the job you are talking about is one which an established local builder will have done hundreds of times, and could practically do in his sleep.

You will need to provide drawings to your council's Building Control Office, you can probably do them yourself with a tape measure for the house and a ruler for the drawing. A3 paper will be OK. You will have to look at the floorboards to see which way the joists run, and preferably lift a board to measure a joist and include the joist dimensions in your drawing.

Your builder will probably be able to tell you what you need in the way of piers, padstones and steel. You might even be able to crib the design by looking online at your council's website and downloading a similar job. Look at local streets with houses similar to yours. The builder will probably over-specify a bit "to be on the safe side." A local draughtsman or engineer will find it equally easy but should have more precise calculations.

the details i.e piers/padstones/steel are pretty much always the same so builder should have no problem of constructing it with or without engineer input.

The most important info you need from the engineer is the size of steel based his investigation and calculation. A competent builder can take his best guess with his exp and "most of time" he will be right