Written by Sam Hills
Introduction
Throughout this article, we will be delving into the characteristics of a half-house; how to identify one and its design considerations. These types of homes are adjoining properties that are separated by a party wall, which is a shared wall acting as the boundary between two properties.
A half-house has one key feature that differentiates it from standard semi-detached or terraced homes: it has a party wall formed from a single leaf of masonry or timber studs which are wall constructions usually associated with an internal partition wall.
Half-houses are created when an existing house is split into two separate homes, although, it is not uncommon to see a line of terraced houses which were likely built as half houses originally. This may be due to cheaper construction by saving materials.
How a half-house can be identified visually
Before highlighting the elements commonly seen in half houses, it is worth noting that any single feature mentioned can be found in a ‘typical’ house too. However, a house with a combination of the features listed below is likely to be a half-house.
Visually, there are two traits that can be identified without even having to go inside. Firstly, one common tell-tale feature is when there is either no parapet wall or a thin parapet wall. Looking at traditional terraced or semi-detached homes with solid masonry party walls, you will notice a small brick wall that will extend above the roof level. This is built up from the party wall throughout all levels, so is a key indicator of the wall construction separating the two homes. As a half-house has a single skin masonry or timber stud party wall, there would not be a thick brickwork parapet.
The second external visual identifier of a half-house is looking at the front door. If two homes have a shared front door, leading to a corridor that separates their different homes, this could indicate a half house. The reason for this is that the party wall above the corridor needs to be supported and is likely to be of lighter weight construction.
Image above – Shared front entrance, with no parapet wall between at roof level. There are parapet walls on the other party wall on both properties
Within habitable internal space, you’re not going to see any obvious elements to suggest that your building is a half-house. Although, a quick investigation of the loft can unravel some unusual characteristics of a terraced or semi-detached house, one characteristic being an open loft. If there are no partitions between you and your neighbours in the loft space, this means you have a shared loft and possibly a half house. This is in contrast to a more common party wall construction, where solid brick is built all the way up to, or higher than, the roof level meaning that your loft space is separated from your neighbours’. If you find you have a shared loft you will want to get fire-resistant partitions put into place as it can be a safety risk whilst also affecting the value of a house.
The second feature which can suggest your home may be a half-house is if the partition wall is formed from timber. As mentioned regarding parapet walls, you’d expect a solid masonry party wall to be built up to roof level.
Take a look at your property externally and in the loft to see if you can find these features.
Would you like some help in figuring out whether you have a half house? Email us at info@blueengineering.co.uk to arrange a site visit with one of our engineers.
How a half house can be identified physically and by sense
Although not obvious from the outside of the property, both physical and sensory findings can tell you a lot about your home. A timber stud party wall is likely to indicate that your home is a half-house. The quickest way to get a feel for this is by knocking on the wall, which you should check on both the ground floor and above as this can change at different levels in a half-house property. A hollow sound would suggest a timber wall, whereas a solid thud and feel would indicate a masonry wall, though this could still be a single leaf of masonry. Take a walk around your house and compare the feel and sound of external walls to internal ones. If your home has both masonry and timber walls you will be able to tell an obvious difference.
By sense, it’s not something you can investigate at whatever time you want but more one that you will have experienced throughout your time in your home. The two senses which may trigger your half-house sixth sense are smell and sound. A thin stud wall or masonry wall will have less insulation than a thicker one and may create more of a link between the structure of your home and your neighbour’s resulting in some shared senses. Can you hear your neighbours talking, watching the television or walking up the stairs? Can you smell your neighbour’s cooking or indoor smoking?
If you are considering renovating your home and you believe it is a half-house, you can book an assessment with us to discuss the safest methods for renovation. Email us at info@blueengineering.co.uk
How it affects the design of structural works
The type of party wall in a half-house can spark up some innovative thinking as its ability to take and spread load is different to a usual party wall; read below to see how it can affect different types of renovation works.
Do be aware that where structure bears onto the party wall, a party wall surveyor will need to be consulted. You can read the party wall guide here.
Loft conversions
A loft space being converted into a habitable space is where it can become difficult, but rest assured there is always a way. For most loft conversions, beams will span between the party walls at both loft floor level supporting the floor joists and at roof level to support the roof joists/rafters. However, in many half house cases, it is difficult to justify load going into the party walls and there are solutions around this.
Image below – A typical loft conversion with beams spanning onto party walls.
To avoid too much load going down the party wall, a front-to-back frame can span from the front wall to the rear wall, or full height columns from the ground floor that go up to the loft level. Therefore, the beams would fix to these steels ensuring the load is not bearing onto the thin party wall. This would add to the cost of the project due to the extra steel and potential foundations required but can make it easier to incorporate architectural features with more freedom.
An alternative to this would be to span the floor joists from the bressummer beam, which is a beam spanning over the bay window, to the spine wall, which is the main, usually central internal load-bearing wall. Having the floor joists spanning between the bressummer beam and spine wall means that any steels that span from party wall to party wall are not required. This would save money on steelwork as only a bressummer beam replacement would be required, however, it is likely to require deeper joists due to a longer span which can reduce the floor to ceiling height in the loft. The additional load on the spine wall can also cause movement resulting in cracking to the finishes at lower levels. The ridge beam can then be supported on a timber post on the narrow party wall, if adequate, which can be shared with the neighbour if they plan to do the same.
Image below – A half-house design with deeper, longer spanning joists bearing onto the spine wall. A timber post is on the thin party wall to only take the load from the ridge beam in the roof.
To book an assessment of your half-house loft, call us on 020 7247 3811. Or email us with your request at info@blueengineering.co.uk
Internal Alterations and Ground Floor Rear Extensions
These types of works pose less of an issue, but still require considerations due to the house structure. Where non-load-bearing walls are to be altered, no additional works are required due to the party wall. However, works that require load-bearing walls to be altered will need to have a new structure installed to support the load above. In some cases, beams may be designed to span into the party wall which is something to be avoided in half houses due to their low load capacity or resistance to buckling. To prevent this, masonry nibs or columns can be specified to support the beam, but this can increase cost and protrude into the living space.
In Summary
To summarise, a home with a single leaf masonry or timber stud party wall is called a half-house. This can be identified through visual inspections from outside the front of the property and in the loft space. It can also be identified through physical methods, requiring an assessment of the sounds when knocking on walls, and by sensory methods such as sounds and smells which are gauged over a longer period of time.
A home with this structure does affect the structural design of the property but there are ways to help achieve your home aspirations. This can include designs involving a front-to-back frame or by installing a floor construction that can span further which prevents the need for steelwork spanning across the width of the property.
If you would like us to have an assessment of your property, or if you would like to proceed with works on your home, please contact us for a quote on 020 7427 3811. Alternatively, you can email us at info@blueengineering.co.uk
