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N1 7GU

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Basement Conversions


Basement conversions are an excellent way of adding all-important space to your property. Any Basement excavation is covered by the Party Wall etc. Act 1996 (the Act).


Depending on the size and footprint of your home, they can allow for the addition of a living area, bedroom, gym, play area, swimming pool, cinema or even under ground parking. 


That said, they are one of the most complex types of construction work or indeed executing the Act you can undertake to your property. With this complexity comes structural risk.


Mitigating risk is going through the necessary Party Wall Surveying procedures to include, underpinning, temporary support, structural calculations, soil analysis, contractor method statement appointing checking Engineers and security for costs. This is not an assignment for an inexperienced Party Wall Surveyor. Our Certified Surveyor specialise in Basement excavations at reasonable prices.


We thought we would take a look at Basement Extensions through a Party Wall Surveying perspective in the hope of helping you understand the type of considerations that Party Wall Surveyors will look at if they act for you or your neighbour.


Security for Expenses


Security for Expenses is formally dealt with under Section 12 of the Act and confirms that an adjoining owner (the neighbouring owner) may serve a formal Notice upon the building owner (the owner undertaking the works) requesting a sum of money, known as the “security” to be held on account during the course of works. This sum is usually substantial and can be calculated in several ways depending on circumstances.


The security is in place to safeguard the adjoining owner in a situation whereby the works start and then remain unfinished for a prolonged period, or if the damage is caused to the adjoining owner’s property. The funds can then be called upon to enable to the adjoining owner to safeguard or repair their structure.


Security for Expenses funds are usually held on account during the works and for a specified amount of time (usually 1 to 6 months) post works.


With Security for Expenses figures often starting from £10,000, this is not a figure to overlook. The funds are normally held in a Solicitors or Escrow account. The account can only be released with two of the three Party Wall Surveyors’ signatures.


Special Foundations


Under the Act there are two types of foundation that can be used to construct the new subterranean Basement walls.


The first type is poured mass concrete, which is a column of concrete engineered beneath the full thickness of the existing Party Wall.


The second type is a narrower support of concrete reinforced with metal. This is known as a special foundation under the Act.


In order to construct a special foundation, the Building Owner will require the consent of the Adjoining Owner under section 7 (4) of the Act.


Obtaining this crucial consent can often be a precarious task and we would advise engaging a specialist Party Wall Surveyor to negotiate this task with either the Adjoining Owner or the Adjoining Owners Surveyor.


Checking Engineers


Checking engineers are usually called upon by the adjoining owner’s Party Wall Surveyor.


The checking Engineers are normally structural engineers. The roll of the checking Engineer is reviewing the building owner’s structural design, calculations, and specifications from the perspective of the adjoining owner’s property and assess the structural risk that the works carry.


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Telephone us on 0207 1180 039 

Text the Duty Surveyor on 07764 589804    9-9 x 7 days a week. 

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