Reduced return on back door

[mfarrow]

Untitled

• mfarrow
• 5 Jan 2015
• 2

Untitled

• mfarrow
• 5 Jan 2015
• 2

Hi

I should have seen this coming really but the council came back on Building Regs plans and noted the reduced return on the back door. We'd like it to be 415mm with a 900mm opening. They've asked for "justification".

What is this usually? It seems from Part A that there is an unclear reason for the 665mm limit, and doing the simple calc in there limits us to 150mm if that wasn't in place.

Is this all down to buckling therefore? and is it:

a) calculatable
b) justifiable without calculation?

We're up to floor already (they didn't have any comments on anything below ground) so keen to continue.

Many thanks

 

[freddiemercurystwin]

Some SE calcs are in order here, BC are unlikely to be satisfied with any other method. Prolly £50-100 if you can find a little one man band type of chap and provide him with all necessary information.

 

[tony1851]

Is the 415mm return internal or external? - seems an odd size (ie not brick-length).

As above, it is 'calculatable', and it actually helps that you have a second storey on top. The issue is not one of the brickwork 'buckling' or crushing, more one of lateral stability under wind load.

The wind load exerts lateral pressure on the return, which induces tension in the mortar joints, which is definitely a no-no. The compressive load from above tends to counter the tension and helps maintain stability.

 

[mfarrow]

Thanks chaps. Yes sorry I meant 440 external.

OK so need to find a friendly one man bander in the Birmingham area. Will start calling round on Monday.

 

[mfarrow]

Bit of a late reply on this one, however speaking to an SE he wants to either write "correspondance" with the ECO, or else insert a steel and calculate. Different price for both.

Is he on the wrong track or were the above answers assuming a steel would be necessary?

It sounds more like he knows it will be OK but can't calculate it without a steel being in place in the calcs?

 

[tony1851]

It's purely an issue of wind loading. By 'steel', does he mean windpost?
If so, those are expensive and - in this instance - almost certainly unnecessary.
Does he know how to prove stability under wind load without additional steel?

 

[mfarrow]

Thanks Tony.

I did say "I believe it's something about wind loading, right?" Which he agreed with, so I think the answer to your last question is NO.

He didn't mention the type or orientation of steel, just that it would be required if he couldn't win the BCO over with words.

 

[^woody^]

For justification, tell the BCO to wonder around Birmingham and see the thousands of houses with no or small returns on the corners, and note how many are falling down since they were built many years ago.

Or every single garage on every new housing estate, which never seen to be questioned.

However the BCO is likely to require a calculation and the engineer won't win him over with just words. It should not need a steel post either, and any slender masonry corner can be justified in a domestic situation

 

[tony1851]

the engineer won't win him over with just words.

+1

 

[mfarrow]

New Answers have come in along the lines of:

- wind's no issue, but you'll need 10N blocks on that corner
- a channel section may be needed worst case (v expensive quote)
- you need my green building advice service
- impossible, needs a steel and BCO won't accept code bridging - move the door

Anyone here wish to tender please?

 

[tony1851]

New Answers have come in along the lines of:

- wind's no issue, but you'll need 10N blocks on that corner
Wind load is the issue, but it won't be critical in your case because the load from above will stabilize the
pier and counteract the tendency to bend horizontally. You don't need 10N blocks either.

- a channel section may be needed worst case (v expensive quote)
Nonsense

- you need my green building advice service
Eh?

- impossible, needs a steel and BCO won't accept code bridging - move the door
More nonsense.

Anyone here wish to tender please?

Seems that the specialists you asked either don't know how to do wind load calcs, or want to charge £££ to
give you a design which will cost you £££££ and be totally unnecessary

 

[mfarrow]

Green building advice man wants to come round and tell me for a not insubstantial fee how bad my BCO approved insulation proposals are and how my 100mm rockwool+90 celotex in the main loft can be improved.

I think I'm going with him though. He's one of the cheapest at 150 notes and confirmed that it won't need any steel inserted.

 

[mfarrow]

I'm at a loss at the moment. The guy we appointed now wants to install 95x45 C24 in the cavity either side of the window. From DPC to wall plate.

I think it's back to the drawing board, or rather yellow pages. What a nightmare!

 

[tony1851]

What in the name of Heaven would sticking two 4"x2"s in the cavity do??

Avoid them like the plague - they don't even know what the issue is.

 

[^woody^]

I think I'm going with him though. He's one of the cheapest at 150 notes

Pay cheap, pay twice.

Why don't you just pay a proper engineer to do the calcs that will justify the brick return?