Lintel replacement

[Adam11]

Hi,

I recently posted about a house I'm in the process of buying, which is displaying classic signs of lintel failure above a few windows and primarily the back door.
My question is, how risky would this be considered as a diy job?

I've watched several videos and read multiple tutorials about lintel replacement and I'm very confident in undertaking this task.
I've received quotes for a platform, acrow bars and strong boys, as well as sizing windows and such.
I've read over building regulations, and believe I have a firm understanding as to what I'm getting myself into and I still don't feel like it's as big of a task as some family/friends are making it out to be.

To my understanding, and what has been mentioned on here previously, the lintels support a triangular formation of bricks above, and providing they're supported sufficiently prior to the removal of brickwork, there's small, if any, risk of failure in this triangular structure?
From here onwards, to my understanding, it effectively becomes a matter of removing the brickwork beneath the strong boys, removing the older lintel, and then replacing it with a newer lintel and if required providing a new cavity tray.
Once this is done, building back the bricks removed and leaving supports in place for 24hrs prior to removal to ensure that the mortar sets without any compaction and potential structural deficiencies where the mortar has compacted.

Can I ask, is my understanding of this accurate and how feasible is this?
I'm quite handy, although never having done anything of this nature previously.
My ambition is ultimately to buy and restore properties in future, so it's inevitably something I'll be exposed to and will be required to handle.

Thanks in advance for any support and answers.
Adam.

 

[^woody^]

No that's a simplistic view.

The triangle can drop and the sides can fold in too, causing stepped cracking sideways.

Then there is the inside leaf. Is a floor or ceiling supported by the lintel, typically the inner leaf is loose and more liable to drop and harder to make good. If not supporting, is a parallel joist blocking access?

Strong boys should be for single leafs only, otherwise use needles.

Is a cavity tray required? If so, more of the wall needs to come out.

 

[Adam11]

No that's a simplistic view.

The triangle can drop and the sides can fold in too, causing stepped cracking sideways.

Then there is the inside leaf. Is a floor or ceiling supported by the lintel, typically the inner leaf is loose and more liable to drop and harder to make good. If not supporting, is a parallel joist blocking access?

Strong boys should be for single leafs only, otherwise use needles.

Is a cavity tray required? If so, more of the wall needs to come out.

Thank you for your reply, it's very informative.

You mention the sides sagging in, but from a structural standpoint wouldn't that imply insufficient support? If the load isn't spread evenly, or supported, wouldn't that be the point in time where there's a failure and the load attempts to disperse itself?

I suppose the cavity tray in itself isn't absolutely required, in regards to the solid plastic cavity trays - I've seen this is more commonly done with what seems to be a black PVC sheeting, which protrudes slightly beyond the 150mm specifications on either side of the window.

I can't actually see all of this yet, given we haven't yet got the keys and in turn, I'm not able to make any intrusive investigations.
From what I've seen online, however, it seems that there's typically an angled lintel in place that supports the outer leaf and a concrete beam that supports the inner leaf in properties of this age (1965). This isn't intended as a statement but a means of conveying where my understanding is, and highlighting gaps in understanding/knowledge.

I'll attach images because the surveyor's report has indicated the potential of no lintels being present and with the brickwork being in soldier pattern/type as well as no signs of a protruding lintel, or any rust, I believe this is a large possibility.
I have read and been told that in houses of this age (around 1965 construction) metal or wooden window frames were used and considered part of the supporting structure so no lintels were used. When double glazing is provided, it's often overlooked in putting in a lintel although required.

The extent of what I can see is in the image attached below if this is of any use?