Changing the internal ‘flow’ of a property can be one of the best ways to transform its appeal without spending a fortune. Knocking through interior walls is potentially a great way to create a feeling of light and space — sweeping away cramped, dark and dingy rooms. For example, in properties with tiny kitchens, taking out the wall separating this room and an adjoining dining room can dramatically improve the layout at minimal expense compared to the cost of building a new extension.
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But inevitably, any job involving indoor demolition is going to come with a number of health warnings. For a start, internal walls can play an important role in holding buildings together, so in some cases, ripping them out can be structurally unwise. In period properties there can be a real danger of creating a sterile environment devoid of historic features and original layouts that many buyers demand.
However, as long as they’re carefully planned, layout alterations can be highly successful at overcoming drawbacks with the original design.
Taking down or altering internal walls isn’t an activity that normally concerns the planners, unless, of course, you’re working on a listed building. However, before making any sort of structural alteration a Building Regulations application must be made. Building Control will then inspect the work on site and ultimately issue a completion certificate.
In most cases you will also need to consult a structural engineer to design a suitable beam or some other supporting structure so the remaining loads are safely transmitted to the ground.
Before demolishing an internal wall it’s also worth considering whether it protects you from fire. For example, where the loft has been converted, the walls around the staircases offer protection, allowing you to escape in the event of a house fire. Altering these walls will again require Building Regulations consent, even if they’re not load-bearing.
On a similar basis, should you want to convert the loft in the future, partition walls that separate entrance halls from reception rooms are best left intact, since they form a ready-made fire escape corridor to comply with Building Regulations.
In terraced or semi-detached houses, where new beams need to rest in the party walls that separate you from the neighbours, it’s also advisable to first talk to a specialist Party Wall surveyor to ensure compliance with the relevant legislation.
It’s not unusual when buying a property for the conveyancer to glumly announce that there is no evidence of Building Regulations consent having been obtained for structural alterations. Even though there may be no apparent defects, if there is no completion certificate to prove that the work was properly carried out, this could be an accident waiting to happen.
In this situation the best course of action is to contact Building Control and arrange an inspection. At worst you may need to obtain a Regularisation Certificate, which is the equivalent to making a retrospective Building Regulations application. This normally requires a certain amount of physical opening up of the work to establish that it is structurally sound and verify compliance; the cost of making good afterwards will be down to you.
Be prepared for the dust and mess created by knocking through
Identifying Load-bearing Walls
Some internal walls are fundamental to the structure of the house, whereas others simply divide up the interior space and are relatively straightforward to alter or remove.
Depending on the age of the property, the internal walls will be built of either solid masonry (brick, block or stone), or of lightweight timber stud or metal frame construction; sometimes a mix of both of the latter. As a rule, older, pre-1970s homes tend to fall in the solid masonry camp (which homeowners tend to prefer because it’s easier to fix things to them and they have better soundproofing qualities).
Conventional wisdom has it that if you tap a wall and it sounds hollow it’s just a studwork dividing wall. In fact, some stud walls are load-bearing. Conversely, solid masonry internal walls aren’t always ‘structural’ — some were built as simple partition walls. If in doubt, the best advice is to consult a structural engineer or building surveyor, but in most cases it’s best to assume a Building Regulations application will need to be made.
As a general guide, to see if an internal wall is load-bearing, you need to check if it’s supporting any of the following:
In older houses the roof structure often relies on support from an internal wall. More modern roofs with W-shaped roof trusses (introduced in the late 1960s) are designed to span right across the house from the main wall to another without internal support.
Floor joists rarely span more than about four metres without support from an internal wall or beam. Look for nail runs in floorboards to identify the direction the joists are running in (usually at right angles to the direction of the floorboards).
Loadings from walls above:
Ground floor walls often continue above as bedroom walls. However, sometimes upstairs walls are offset or supported on a beam. Most modern houses have lightweight stud walls to the upper floors.
In older houses, internal walls often provide ‘lateral support’ helping to tie together the adjoining walls either side.
Builders tend to refer to internal wall demolition jobs as ‘knock-throughs’. This might involve anything from just cutting a new door opening, through to the complete removal of an entire wall.
Building Control normally require a structural engineer to specify an appropriate beam or lintel, and this should be done before getting quotes from builders so they know how much to charge.
As with most jobs, there are a number things that can sour relationships unless properly factored in from the outset:
- You can never overestimate the amount of dust and mess involved with indoor demolition, so it’s worth having the builders erect dust screens across each room.
- Check that quoted prices allow for the repositioning of any radiators, switches and electrical sockets.
- Ensure all necessary plastering and decoration to areas of exposed masonry is included in the price.
- The old skirting boards should be retained so that everything matches when the joinery is made good.
- When a wall is taken out, the new steel beam will have to rest on something at each end, so a small end section of the original wall (known as a ‘nib’) may need to be left in place.
For new door openings, the upper part of the old wall will be left in situ above the new opening (known as the downstand). But where an entire load-bearing wall is removed, a ‘clean sweep’ at ceiling level may not be possible as the new beam will normally be visible. Bear in mind that steel beams need to be boxed in with plasterboard to comply with fire regulations. If a continuous ceiling is aesthetically important, one solution is to build a new suspended ceiling to conceal the beam.
Once a wall is removed it often becomes horribly apparent that the floor levels in the newly conjoined rooms either side aren’t perfectly aligned, because they were never designed to meet. Even a small difference of a few millimetres will stand out, requiring additional floor levelling work. Similarly, newly exposed wall surfaces may require the attention of a skilled plasterer.
A steel lintel resting on padstone engineering bricks supports the new opening
Creating a New Opening
Once the structural engineer has calculated the loadings and come up with a suitable solution to satisfy Building Control, work on site can proceed. But before any demolition work is carried out, the masonry above must be temporarily supported while a slot is cut for the new beam or lintel. This slot normally needs to extend either side of the opening with a bearing of at least 150mm. To spread the load, additional support will be needed under the ends of the lintel, such as padstone engineering bricks. The new opening can then be cut out underneath.
Bear in mind that party walls in older properties aren’t always ideal for supporting new loadings. For example, some were built one-brick thick (about 100mm), and may not be sufficiently strong for this new role. In which case, it may be necessary to build new brick piers or install steel columns to support the new beam — which could mean having to excavate small foundations internally, adding significant expense and disruption.
Specifying Steel Lintels
“To design and install a beam that can support tens of tons of building and prevent it from falling down can, in theory, be done by anyone regardless of their qualifications,” says chartered structural engineer Simon Pitchers.
“Self-design can be tempting for a self builder. However, specifying steel members that are safe requires expertise that will be beyond the capabilities of most self builders.
“The size of a steel beam is not determined just by its span, although this does have a significant effect. Its size is also governed by many other factors such as the type of load and the effect of the beam on the foundations of the building.
“Beam design is a complicated business and an error can be disastrous, from both a financial and safety perspective. There is software available that is said to provide design calculations for steel beams, and while this may be useful in the simplest situations, the opportunity for error in terms of over-design (a beam being more expensive than necessary) or under-design (a beam being unsafe) is significant.
“A professional steel beam design from a chartered structural engineer can be purchased for a few hundred pounds. Many manufacturers of proprietary steel lintels will employ engineers who can design their products to suit specific situations. They will often provide this service free of charge, again avoiding the need for a self-builder to attempt this specialist exercise.
“Visit the Institution of Structural Engineers’ website to find out whether a structural engineer is needed for your project.”
|Cost of Associated Work|
Cost (incl materials and labour)
|Demolish wall and clear debris into skip:|
|Quoin up and make true the end of the wall||£65/m²|
|Open up a kitchen/dining room with a square opening 1.8m wide to load-bearing wall||£1,200|
|Add on more for the following:|
|Form a new single door opening in an internal wall (cut opening, fit concrete lintel, quoin up jambs, fit 50x100mm softwood frame, stops and architrave, and make good finishes):|
About the Author
Chartered surveyor Ian Rock is director of the survey price comparison website Rightsurvey and author of the Haynes Period Property Manual.
Image: John Lawrence