Full width 6 metre knock through

[tony1851]

Sometimes, Building Control officers will suggest a steel section-size they would be happy with, though it is not their remit
and they should not be taking that responsibility.
If you want to go the full width, chances are they would want some figures, which will be checked by their own engineers. It's not just the steel size, but the padstone sizes also.

On a separate note, why not make it easier for yourself and leave a short pier each side - say one block width. If you offer to do that, and also diaphragm your new (lean-to?) roof with plywood to stiffen the structure, you may get them to agree to not have a goal post structure.

 

[sambotc]

Hi,

Yes, I'd be quite happy with a pier each end if it simplified the project. I guess the next step would be a 1 hr consultation with the building control officer, which I think they offer for free.

I'll look up diagramming a roof !?! but yes, it'd be a lean-to type roof.

Thanks for the help

Sam

 

[noseall]

Surely the 'borrowing' of any neighbouring structural buttressing will be ignored by any half decent SE's in view of the fact that the neighbours could potentially do something similar to the OP.

Goal posts sounds like an option.

 

[tony1851]

As well as a (say) one-block pier internally each side, he would be allowed to take into account the thickness of the party wall each side (in terms of checking lateral stability).
If there are other internal block walls at ground-floor level running parallel to the rear wall; and if the new lean-to roof is diaphragmed; and if there are reasonable returns in the outer wall of the extension, I would say that lateral stability should not be an issue.

 

[sambotc]

There is a wall 2.7 metres back from the wall in question that is a load bearing internal wall running parallel.

 

[chappers]

I would speak with an SE, building control won't go against his calcs.
You can speak to building control if you like, but for something that size I doubt they would take on the responsibility of specifying the beam and would just tell you to see an SE anyway

 

[Doggit]

You say that it's a cavity wall construction, but do the lintels span the cavity. If they don't, then it's manageable - just. But if they do, then you've got to work the inside and the outside together. If the lintels are separate, then start on the outside wall, then do the inner one, but if the lintels have been poured in situ, then they very likely straddle both walls, so you'd need to put tall boys on acrows in the outer wall at the same time. And that'll make it fun and games trying to maneuver a 6m steel between 2 sets of acrows.

If you built side supports to take the weight of the steels, then you'll have fun and games tying them in to the side walls, and building control may want them to go off for a few days before the steels go in, so using side steels to take the weight will make it a more expensive, but quicker. Getting the concrete lintels out will be a bugger of a job, as they may well be heavier than the steels, so you need a way of supporting them, and cutting them out in sections. You'll very likely need a party wall agreement with the neighbours, so check with them first to see how they'll react.

You could take one of the windows out and inspect the underside of the lintels, or use a core drill to take out a section, and have a look that way. And yes, call building control in to get their opinion on it ASAP

 

[sambotc]

Party wall is something I'm trying to avoid, well, work around.

The neighbour on the left can be pretty awkward at times for no apparent reason. I am going to discuss the plans with them once I have a form idea on how it will go together.

However, if they decide to play up, could building piers to support the lintel on and therefore having no influence on the party wall be a work around?

I'd hope to find a resolution that suits everyone but there is no reasoning with unreasonable people!

 

[wessex101]

Edit: Just realised I was responding to an old post on previous page, what a fool.

 

[sambotc]

It appears to be 2 X 150mm ish wide

lintels separated by some form of DPC rather than one which should make life easier!?

 

[Doggit]

Okay, you've got a gap between the inner and outer walls, so you can do then one at a time. Outside one first, then the inner one. If you use piers, you may still need a party wall agreement because you're attaching them to the party wall, but as you're not cutting into his wall, it'll be minimal aggrevation for him, and very little cause for him to complain - although he'll very likely look as hard as he can to do so. Will the other neighbor give you access to his garden to slide the steelbetween the acrows.

Building control will overestimate the size of the steel, just to play safe, so whilst getting the calcs done will cost you, it may well cut down on the size required. See what building control wants when they turn up for the initial consult. If you're putting in piers, then BC may want you to dig out in front of the piers to check the foundations, as all the weight is being pushed down on to that point.

 

[tony1851]

If there is a sufficient return remaining at each end, there may be no need for new piers. That being the case, there would be no need for pad foundations as the bonding effect of the blockwork would distribute the load from the beam-end into the party wall. The further the load goes down and outwards, the more foundation there will be to support it.

In my experience, a building control officer is unlikely to go round and freely offer advice, particularly prior to an application being made.

 

[sambotc]

Thanks for the advice, very useful.

What's the available space between the strong boy props and the wall normally? I had imagined placing the steel on the floor right to the wall first, then once the existing was out of the way lifting up and sliding in!?

Access via the other side should be an issue.

 

[sambotc]

I've checked the council website and it may not be a site visit but an hours 'consultation' for free.

It's awkward as there's no point paying if it's not reasonably possible. Perhaps I could take some photos and visit them instead.

 

[Doggit]

The strong boys sit on top of an acrow, which then sit about a foot out from the wall; they can have a tendency to twist a bit as you tighten them up if they're not pushed in very far, and that makes them even closer. Not a bad idea putting the steel on the floor, and then putting the acrows up, as long as it doesn't get damaged when the concrete lintel comes crashing down, because that's going to be heavier then the steel. Not sure whether you can get the steel done in 2 sections and bolted together and welded. Have you worked out how to get the concrete lintel out. Not sure if you could use a few acrows to support it and slowly take it down a foot so you can cut it into sections.