Raising Party Walls in timber
PARTY WALL etc ACT 1996 Section
2(2)(a)
Raising of party walls
In the aftermath of the Great Fire of
London in 1666 the Authorities legislated to prevent a re-occurrence of
the catastrophic damage by requiring future construction to be built in
masonry. Until the repeal of the Constructional By-laws made under
the London Building Acts an owner wishing to raise a party wall was
obliged to do so in brickwork or stonework and furthermore to do so
above the roofline as a parapet. Apart from the fire-resisting
qualities parapets provide a harmonious architectural addition to
terraced properties.
Some building professionals interpret the
London Building Act requirements as a precedent for party walls to be
raised in masonry; however, others take the view that modern materials
enable the wall to be raised in clad timber framing.
When applied to loft extensions Planning
Authorities have differing interpretations of Permitted Development
rights. Section 38 of the Law of Property Act 1925, defines a party wall
as a wall being jointly owned, severed vertically at the centre line but
with the benefit of mutual easements of support. The Planning Acts
neither define party walls, boundaries nor curtilage, thus when
considering whether raising the full width of a party wall as part of a
loft extension is Permitted Development, the law is unclear. In 2000 the
London Borough of Enfield refused an application to certify Lawful
Development for a loft conversion, the dormer cheeks of which were
raised the full width of the party wall. The refusal was on the grounds
that the development was beyond the curtilage of the subject house and
therefore not Permitted Development. On Appeal the Inspector disagreed
with the Council on the grounds that the curtilage had to include the
full width of the party wall, without which the house would be
incomplete. A similar decision was reached in 2009 against the London
Borough of Barnet. In 2010 the Court of Appeal, quoting the Oxford
English Dictionary, held against the London Borough of Waltham Forest
that the curtilage of a dwelling house included the full width of the
party wall. Planning Decisions are not binding; however there appears to
be a consistency in the decisions from which it is reasonable to suggest
that a party wall falls within the curtilage of a building, at least for
the purpose of planning law. Regrettably many Local Planning Authorities
still disagree, leading to curious construction techniques and
differences in the interpretation of Section 2(2) (a) of the Party Wall
etc Act.
The Building Regulations permit the
construction of timber framed party walls. Additionally, brick/stone
party walls are more often ‘thickened’ using timber battening (ie dry
lining, soundproofing) and not the same material as used in the original
wall. Accordingly, is there any reason why a brick/stone party wall
cannot, where appropriate, be raised in timber?
The raising of a party wall in brickwork
is arguably the best way of achieving a satisfactory aesthetic
appearance and fire-resistance, but it has to be acknowledged that a
112.5mm or 225 mm thick brick wall is neither waterproof nor sufficient
to comply with today’s requirement for energy conservation. Siting
of efficient damp proof courses can also be
challenging.
There are few, if any, grounds to
challenge notices to raise a party wall in masonry and access to carry
out that work. Importantly the raising in masonry of a party wall
facilitates the ability of both owners to subsequently raise the wall.
Thermal insulation can be provided internally and if properly detailed
the wall can be raised as a parapet thereby enabling a waterproof
junction between flat or pitched roofs and the parapet. The
Adjoining Owner can subsequently enclose upon the raised party wall and
pay half the costs at the current price.
With the need to increase living space
owners are resorting to adding loft rooms, the cost being significantly
less than moving house and the process is made easier by relatively
relaxed planning policies. To fulfil significant demand loft building
companies are starting up everywhere, some employing designers with
inadequate knowledge of sound construction techniques and the provisions
of the Party Wall etc Act 1996. Loft Companies prefer working in
timber and the “modern” way to raise a party wall is often in
timber-framing. A dormer cheek not built off a party wall will almost
always be built in timber off a double (or even triple) rafter. The loft
conversion is exactly that - a conversion of the loft, which is part of
the roof, and inevitably built in timber. Accordingly, if one is
converting a loft made from a timber roof, then the obvious, and often
only material that can be practically used, is timber. The raising of a
party wall in timber to create the cheek of a dormer is merely an
extension of the existing use of timber elsewhere in the loft
conversion. To raise one side where the party wall is in brickwork is an
additional expense, not only in material costs, but also in labour,
involving the need for additional tradesmen, namely a bricklayer, and an
extra day's work.
If properly executed it is possible to
design the raising of a party wall in compliance with the Building
Regulations. It is therefore difficult to argue against raising a
party wall in timber unless it is reasonably foreseeable that an
Adjoining Owner would subsequently be deprived of their right to do so,
or incur additional costs in the exercise of that right. An adjoining
could also serve a counter notice under section 4(1)(a) insisting that
the wall is raised in brick, but that right is of course subject to a
contribution to any additional expenses of work, pursuant to section
10(9) of the 1996 Act.
To avoid serving notice under the Act
some building designers opt to double up the rafters spanning parallel
and adjacent to the party wall and support the dormer cheeks on timber
framing, the external cladding projecting over half the width of the
party wall. Since the cladding does not bear on the party wall it
cannot be described as the raising of the structure thus there is no
requirement to serve a notice under Section 2 of the Act. However,
the disadvantages are that there is no legal right of entry onto the
Adjoining Owner’s roof for the purposes of construction and also there
is a risk that roofing battens, when cut for the works, may be left
short with inadequate broken joints. On the other side of the coin
the developer does not have to pay for expensive surveying services and
the Adjoining Owner can, at a later day, raise the full width of the
party wall in masonry or timber studwork.
An alternative to framing the dormer
cheek is to raise the full width of the party wall as a double leaf of
timber-framing incorporating the required sound, fire and thermal
insulation, but this involves the Adjoining Owner accepting
the cladding being on their side of the party wall, albeit the removal
of the cladding to facilitate enclosure would be a simple process.
Whether specific consent for the cladding to be on the adjoining owner’s
land is required is a moot point; the tile hanging is merely a form of
weather- proofing of the timber stud wall, in the same way that render
may be for a block wall. It is possible to argue that such tile hanging
is an integral part of the wall, namely it’s weatherproofing. In Section
2 of the 1996 Act there are clear provisions designed to facilitate
works of weatherproofing, thus the Act is drafted to enable works for
such purposes.
The “third” method involves serving a
notice to raise the party wall in timber but in such a manner as to
facilitate the Adjoining Owner replicating the work without incurring
additional costs. The advantage to the Building Owner of serving a
notice to raise in this manner is the right of access under Section 8 of
the Act. Furthermore, it becomes possible to determine a long-term
solution to detail the junction of dormers if and when the current
Adjoining Owner carries out reciprocal development.
It is submitted that an acceptable method
of construction, that is to say in compliance with Building Regulations
and advantageous to the Adjoining Owner, is (viewed from the Building
Owner’s side of the party wall), as follows: -
- An insulated plasterboard system cladding
the existing party wall as well as the internal face of the
timber-framed dormer cheek providing the necessary fire resistance,
thermal and sound insulation and incorporating an integral vapour
control layer all in the form of:
- Kiln-dried and regularised
timber studwork of minimum finished section size 100mm x 50mm, ideally @
400mm centres, but sized to suit the dormer construction, by a
structural engineer or other suitably qualified designer.
-
Non-combustible insulation, such as Rockwool, to fill the gap between
the studs.
- Structural grade plywood sheathing with a
weather-resistant glue line of thickness to be determined by that
necessary for the loadbearing parts of the dormer construction.
-
15mm thick calcium silicate board to achieve the required fire
resistance for the overall system, as confirmed by appropriate available
fire test data sheets.
- Breathable membrane.
- Vertical
counterbattens fixed through the boarding/sheathing in line with the
vertical studs behind to provide the necessary drainage and ventilation
path behind the horizontal battens.
- Horizontal tile-battens and
tile/slate weathering.
It is, however, the Designer's
responsibility to check with Building Control that the above
specification is acceptable in their area. The ultimate aim where
both owners develop is to provide a timber framed party wall in
compliance with the Building Regulations and initially without
disadvantaging the Adjoining Owner.
To provide the opportunity to form a
long-term working detail where both owners have developed their dormers
at the boundary, the head of the dormer cheek should ideally be
constructed with an upstand above roof level, in the order of 150mm
high, which can be flashed over to form a weathering joint. Where
owners wish to join their dormer flat roofs the omission of this, or a
similar, detail can and does lead to disputes. It is appreciated,
however, that to incorporate this detail in the dormer design may depend
on the relationship between the height of the dormer and the ridge
line.( normally 150mm)
This Article describes some of the common
approaches to building dormers; however, many old terraced buildings
were built without party walls in the roof attics, or the party walls
are only half brick thick. In these circumstances some local authorities
take the view that the raising of the party wall shall not be carried
out to a lesser standard than used in the original wall construction
which, if steps are not taken to improve insulation, implies the
potential for serious inconvenience to the Adjoining Owner.
In conclusion, provided an Adjoining
Owner is not disadvantaged by the actions of the Building Owner, the
raising of a party wall in timber framing in compliance with Building
Regulations is acceptable.
Keith Douglas FRICS. MCIArb
Stuart Frame. Barrister
Acknowledgments.
Phillip Cane MCIOB
Robert Moxon BSc. FRICS. C.Build E.
FCABE. CMaPS
John Naish BSc. FRICS. MCIArb
14.11.2018