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Basement Conversions

Jan 8, 2023


Thank you for clicking on today’s Property Surveying blog post, today we are going to be looking at the typical procedures and protocols that will come into play if a building owner is planning on undertaking a basement conversion or basement extension to their property. 

Under the Party Wall etc. Act 1996, if a building owner is planning on undertaking a basement conversion and that basement conversion is within 3m of an adjoining property, from a legal perspective they will need to serve a Party Wall Notice under the Party Wall etc. Act 1996.

Whenever high risk works such as a basement conversion are being undertaken, it is normal and to be expected for the adjoining owner to dissent to the Party Wall Notice.

In all likelihood, that dissent coming by way of their own party wall surveyor’s appointment.

As part of the party wall surveyor’s jurisdiction and protective input, there will be various different provisions that are followed in the lead up to the Party Wall Award.

We are now going to take a brief look at these, in the hope that they will fully advise you as to what to expect, if you are planning on undertaking your own basement conversion.  Alternatively, if your neighbour is planning on undertaking their own basement conversion.

Security for Expenses

Security for expenses is dealt with under Section 12 of the Party Wall etc. Act 1996.

Security for expenses is the Act’s vessel whereby an adjoining owner can request a sum of money from the building owner prior to the works commencing. 

That sum of money, formerly known as, the security, is in place to ensure that should the building owner commence the works, for whatever reason during the course of them stalling, stopping or delaying them.

From a construction perspective, the adjoining owner’s property could be at risk of failure or collapse.

This is certainly the case when it comes to something like a basement, as this will not only include deep excavation, but also a degree of underpinning to the shared party wall if indeed the works are being undertaken to a terraced or semi-detached property. 

In theory, the adjoining owner can therefore use the security to safeguard their own property, whether that be backfilling the open excavations, or completing the underpinning in full.

It should be worth noting, that the need to ever use security for this type of scenario is in practice very rare. 

For it really to come into play, the building owner would have had to hit such financial dire straits that they are unable to progress the works.

Security for expenses quantum can range anywhere from hundreds to tens of thousands of pounds. 

Advising Engineers

Advising engineers are another key protective provision that the adjoining owner’s party wall surveyor will rely upon. 

The advising engineer’s role is to advise the adjoining owner’s surveyor of the risks associated with the planned construction work and in particular those works that will structurally affect the neighbouring property. 

The advising engineer is not there to double check the work of the building owner’s engineer, instead they are in place to review and advise the building owner on the approach that the engineer has selected.

Outcome of advising engineer review is likely to be a schedule of comments.

This schedule of comments acting like a dialogue between the building owner’s engineer and adjoining owner’s engineer. 

The end result will be better understanding, equally it could also be light revisions and adjustments to the overall building owner’s structural design.

Advising engineers will not only add cost to the building owner’s proposed project, they will also rightfully incur a fee for which the building owner will be duty bound to cover.

Movement Monitoring

Movement monitoring is an incredibly typical security provision that party wall surveyors will request on if indeed basement conversions are being undertaken.

Movement monitoring will see monitoring tags installed in considered positions on the adjoining owner’s property. 

These tags will then be monitored during the course of the building owner’s basement excavations, ultimately ensuring that the movement, if any at all, is at the lowest possible point it can be. 

The beauty of movement monitoring, is that it will give the construction team early notice and information should movement occur.

This will give them the opportunity to down tools, assess what has caused it.  Ultimately moving towards necessary provisions to stop it worsening any further. 

Movement monitoring costs are not cheap. 

In almost all situations the movement monitoring tags will be manually read by a surveyor with a theodolite with those results being compiled and passed back to the respective party wall surveyors.

As a ball park and average, movement monitoring fees for an average basement conversion are likely to be in the region of £3,000-£5,000. 

Schedule of Condition Reports

With all Party Wall Awards that are agreed, Schedule of Condition reports will very much usually form part of them.

However, when the building owner is planning on undertaking a basement conversion, the Schedule of Condition report is going to be significantly thorough and robust than it would be if they were doing more conventional construction works.

This not only means additional time on site for the party wall surveyors to complete the Schedule of Condition report. 

It will also translate to a slightly higher party wall surveyor fee, as ultimately the party wall surveyor would have spent additional time on the matter. 

It is worth adjoining owners being aware of the need for a Schedule of Condition.  In many cases, adjoining owners can become confused at the need for surveyors to go through each and every room of their property in a slow methodical manner to record its condition pre works.

Basement conversions are naturally going to be towards the upper realm of the risk spectrum.

However, it should be worth noting that these days basement conversions are actually a conventional form of construction. 

Generally speaking while basement conversion costs will run up into the hundreds of thousands, it can still be a lot more cost effective than paying agent’s fees and stamp duty in moving property.

For that reason a lot of property owners these days are tending to opt for going through a basement conversion, as they can dramatically improve and change the way that their property is set out.

If you would like to discuss basement conversions with our team of experienced and qualified party wall surveyors, please feel free to give us a call today, we will be more than happy to assist and advise you.

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