Structural Design for a terraced house side return extension
Anonymous user 23/02/2024 - 3.36 PM
HI All,
I have a terraced house c.1900, which I'd like to build a side return extension, and remove the two external walls, which would then be enclosed in the new extension. I'd also like a bifold door fitted across the rear of the house.
The structural design is for two sets of goalposts (3 beams each = six beams) which span the whole width of the house - one at the front and one at the rear of the side return, plus a steel beam between the two sets of goalposts. Total seven beams, and four concrete pad foundations for the verticals.
Prior to this design, based on discussion with the architect, I had expected beams to sit on stubs of the existing walls, with one new foundation, at the rear outside corner of the side return. Total three beams. In discussion with builders (and following an independent estimate), the design as it is is proving prohibitively expensive - twice the upper end of a typical £/msq calculation.
I've queried this with the engineer, but am told it's the only way to go. It seems he has no incentive to design anything that isn't the most robust option with no economic consideration. Or it might be the right and normal design. I'm further concerned as he hasn't conducted a site visit (his quote said he would) so is telling me this is the only option without having seen the property.
Questions:
1. Is the two sets of goalposts with a connecting beam the common way to do a side return extension in an old house?
2. Is a Structural engineer not doing a site visit a red flag, or is it typical for a simple job?
3. Am I able to influence the design in any way, or is the structural engineering process a take-what you're given one?
Any thoughts gratefully received,
Are you a tradesperson and able to answer this question?
I would trust your engineer. Things must be done properly. If it were to fail you would destroy the neighbours properties as well as your own. What you have described sounds quite normal.
As for a site visit he probably didn’t see it necessary and got the information another way. Or failed to produce a successful covid risk assessment that would allow him to do so.
Not many people can afford what they can imagine. Try and just go with the flow, your relationship with the workforce including the engineer is crucial to the success of the project.
Answered5 October 2020
2
Anonymous user
You can always challenge your engineer. You should just ask him to justify his design and why you can't do what you had planned. If you can try and find a friendly structural engineer who the architect has worked with and get some advice from them?
Henry,
I would add to earlier comments, that if you are not happy with proposed engineering solution, you can always ask for the second opinion, just keep in mind that it could cost a little extra. However, it may result in the desired solution.
All construction professional usually start the project from the site visit for the simple reason - to understand the existing conditions and to avoid unnecessary abortive work. You can always invite the engineer to attend it on most convenient time.
As the client, you can always influence the design but you should avoid providing the specialist answers/solutions if you are not qualified within the field, such as structural engineering. However, the advise is to rely on common sense and to trust the selected professionals, talk to them to understand the problems and proposed solutions.
Hi
This is a way forward if you want a flush openings without any returns on both side of the wall otherwise it can be done without a goal post struture if Engineer leave return on each side with 665mm (need to be structurally check with loadings) to satify the enough 3T buttersing of each side of party wall.
The roof type like pitch and flat roof in Wrap around extension in L shaped victorian houses depend upon the structure as well if the roof is pitch then the steel supporting the rear outrigger wall needs to cranked as well.
Site visit is usally not required in these small jobs structural design can be done with drawings provided
