How to Budget for a Wall Knock-Through (Avoid Costly Mistakes)

Know the True Cost Before You Swing the Hammer

Breaking Down the Costs: Materials, Labour, and Unexpected Expenses

A wall knock-through can transform your home, but if you don’t budget correctly, it can also drain your finances faster than you expect. Before you start, you need a clear breakdown of the costs involved.

Materials:

The biggest structural cost in a wall knock-through is the support beam—often an RSJ (rolled steel joist). Prices vary based on length and load-bearing capacity, but expect to pay anywhere from £300 to £1,200 for the beam itself.

Plasterboard, skirting, and finishing materials typically add another £200 to £500, depending on the size of the opening.

If you’re relocating electrics or plumbing, factor in an extra £300 to £1,500, depending on complexity.

Labour Costs:

Hiring a structural engineer to assess your project and provide calculations will cost between £250 and £750. A builder will typically charge £1,200 to £3,000, depending on the size of the wall and the difficulty of the job.

If you need a skip for rubble removal, budget around £200 to £300.

Unexpected Expenses:

Even with a solid budget, costs can creep up. Older homes often have hidden surprises—like unsupported joists, asbestos, or faulty wiring. These can add anywhere from a few hundred to several thousand pounds to your bill.

Professional vs. DIY: Where to Save and Where to Spend

You might be tempted to take the DIY route to cut costs. But before you grab a sledgehammer, here’s where it’s smart to save and where it’s worth spending.

Where You Can Save:

• Project management: If you’re confident in coordinating trades, you can save £500 to £1,000 by managing the work yourself instead of hiring a contractor.
• Finishing work: Painting, skirting, and minor patchwork can be done yourself, saving around £200 to £500.
• Skip hire alternatives: If you have time, making multiple trips to the local tip could save you the £200 to £300 cost of a skip.

Where You Should Spend:

• Structural work: Cutting corners here is a disaster waiting to happen. A professional builder ensures the wall is removed safely and that the right support is in place.
• Structural engineering: Guessing whether a wall is load-bearing is risky. A structural engineer’s report costs a few hundred pounds but prevents expensive mistakes.
• Electrics and plumbing: Moving sockets, light switches, or radiators should be done by a qualified tradesperson to comply with UK regulations.

Hidden Costs That Could Wreck Your Budget (And How to Avoid Them)

Many homeowners underestimate the full cost of a wall knock-through because they don’t account for hidden expenses. Here’s what can catch you off guard.

Building Regulations and Approval Fees

If your wall removal affects the structural integrity of your home, you’ll need building regulations approval. This costs between £200 and £500, depending on your local council.

If you live in a listed building or a flat, additional permissions may be required, which can add to the cost and timescale.

Structural Surprises

Not all walls are straightforward. Cavity walls may need additional insulation to meet modern building regulations. If the existing structure is weak, extra reinforcement may be required, adding £500 to £2,000 in costs.

Matching Flooring and Décor

An open-plan space looks fantastic—until you realise your old flooring stops where the wall used to be. Matching new flooring to old can be tricky and expensive, often adding another £500 to £1,500 to your budget.

Temporary Accommodation Costs

If the work takes longer than expected, you might need to stay elsewhere. Even a few nights in a hotel or Airbnb can add £50 to £150 per night to your expenses.

How to Avoid These Budget Killers

• Get a full structural survey before starting. This helps identify any hidden issues.
• Request a detailed breakdown of costs from your builder to avoid unexpected add-ons.
• Have a contingency fund of at least 10% of your budget to cover any surprises.

A well-planned wall knock-through can add space, light, and value to your home. But without proper budgeting, it can quickly spiral out of control. Plan ahead, know the costs, and avoid the common pitfalls to keep your renovation on track.

Smart Budgeting Strategies to Keep Costs Under Control

How to Get Accurate Quotes (And Spot Overpriced Estimates)

Getting a quote for a wall knock-through isn’t as simple as asking one builder and calling it a day. If you want to avoid overpaying—or worse, getting hit with surprise costs—you need a strategy.

Start by requesting at least three quotes from reputable builders. Make sure each quote includes a breakdown of costs for materials, labour, and structural support. If a builder gives you a vague estimate without details, that’s a red flag. You need transparency.

Ask each builder if their quote includes VAT. Some don’t include it upfront, which makes their price seem lower than it actually is. You don’t want a shock when the final invoice arrives.

Check if site preparation and clean-up are included. Some builders charge extra for waste removal, which can add hundreds to your final cost. If it’s not in the quote, ask for it to be included.

Compare the cost of structural support. If one quote is significantly cheaper than the others, find out why. Some builders cut costs by using weaker beams or skipping crucial reinforcements. A poorly supported wall knock-through can lead to cracks, sagging ceilings, or worse.

Always check reviews and past work. Look for builders with experience in structural alterations, not just general renovations. If possible, visit a project they’ve worked on. A well-done wall knock-through should look seamless, with no visible cracks or uneven finishes.

The 10% Rule: Why You Should Always Budget for Contingencies

No matter how well you plan, unexpected costs will come up. A hidden pipe inside the wall, crumbling brickwork, or outdated wiring can add hundreds—or even thousands—to your budget.

The best way to handle this? Always add at least 10% to your total budget for contingencies. If your knock-through is estimated at £5,000, make sure you’ve got at least £5,500 set aside. If it’s £10,000, aim for £11,000.

This isn’t wasted money. If you don’t need it, great—you’ve got extra cash for decorating or upgrading finishes. But if something goes wrong (which happens often in older UK homes), you won’t be caught off guard.

Some of the most common unexpected costs include:

• Structural surprises – Old homes often have hidden issues like weak brickwork or rotting beams. These need fixing before you can proceed.
• Plumbing and electrics – If pipes or wiring run through the wall you’re removing, they’ll need rerouting. The cost depends on complexity.
• Building control fees – If your knock-through needs approval from building control, factor in inspection fees. These vary by council.
• Finishing costs – Once the wall is down, you’ll need plastering, skirting boards, and possibly flooring repairs. These can add up.

By budgeting for surprises, you stay in control. There’s nothing worse than running out of money mid-project and having to cut corners.

Phasing Your Renovation: Spreading Costs Without Compromising Quality

If your budget is tight, you don’t have to do everything at once. You can phase your renovation to spread the cost over time.

Phase 1: Structural Work – Prioritise the knock-through itself. Get the wall down, the structural support in place, and any essential plumbing or electrics rerouted. This is the most critical stage and should be done properly.

Phase 2: Plastering and Making Good – Once the structure is sound, you can move on to plastering, skirting boards, and any necessary repairs.

Phase 3: Decorating and Finishing Touches – The final step is flooring, painting, and any built-in features like shelving or lighting. If your budget is stretched, you can live with a basic finish for a while and upgrade later.

Phasing your renovation also gives you time to shop around for materials and finishes. If you rush everything at once, you’re more likely to overspend.

For more expert advice on planning your wall knock-through, visit Safe and Simple Wall Knock-Throughs for a Bigger Home.

Maximising Value – Get the Most Bang for Your Buck

Choosing Cost-Effective Structural Support Without Cutting Corners

Structural support is the backbone of your wall knock-through. Get it wrong, and you’re looking at sagging ceilings, cracks in your walls, or worse—serious structural failure. But here’s the good news: you don’t have to spend a fortune to do it right.

The most common choice is an RSJ (Rolled Steel Joist) beam. It’s strong, durable, and widely used in UK home renovations. But not all RSJs are priced the same. The size, weight, and whether it needs to be custom-fabricated can all impact cost. A standard RSJ for a typical knock-through might cost anywhere from £300 to £1,000, but that’s just the beam itself. Factor in installation and structural calculations, and you’re looking at £1,500 to £3,000.

Want to save money? Ask your structural engineer if a smaller beam with additional support, such as a box lintel, could work. Sometimes, a combination of lintels and beams can offer the same stability at a lower price.

Another option is timber or laminated beams, but these are usually best for smaller openings or non-load-bearing walls. If you’re opening up a large space, steel will almost always be the smarter choice.

Installation costs can also creep up if your contractor has to create padstones (concrete support bases) or if the beam needs to be hidden within the ceiling. If you want a seamless look, you’ll pay extra. A flush beam costs more in labour but gives you a cleaner aesthetic. If you’re on a tight budget, consider leaving the beam exposed—it can add an industrial, modern feel to your space.

Bottom line: Don’t cut corners on structural support. But do ask your engineer or builder about alternative solutions that maintain safety without unnecessary expense.

How a Wall Knock-Through Can Boost Your Property Value (And When It Won’t)

A well-executed wall knock-through can significantly increase your home’s value, but only if it makes sense for your property and the local market.

In the UK, open-plan living is highly desirable, especially in period homes where small, boxy rooms can feel restrictive. By creating a larger, flowing space—typically between a kitchen and dining room—you can add up to 5–10% to your home’s value. That’s a solid return on investment, especially if your renovation costs stay under control.

However, not every knock-through adds value. If you remove a separate dining room in a family home, you might make it less appealing to buyers with young children. In some cases, keeping a degree of separation—through broken-plan living with strategically placed partitions or glass doors—can actually be more attractive.

Another factor? Bedroom count. Knocking through two small bedrooms to create one larger space might suit your lifestyle, but it could lower your home’s market value. In the UK, more bedrooms typically mean a higher asking price, so think carefully before sacrificing an additional room.

Before making any decisions, check local property listings. If similar homes in your area have open-plan layouts and sell for more, your knock-through is likely a good investment. If buyers in your area prefer traditional layouts, you might want to reconsider.

Energy Efficiency and Resale Appeal: Long-Term Savings from Smart Choices

A wall knock-through changes more than just the layout. It also affects heating, insulation, and energy efficiency. If you don’t plan for these changes, you could see higher energy bills—and that’s a dealbreaker for future buyers.

When you remove an internal wall, you’re creating a larger space to heat. In older homes, this can lead to draughts, uneven temperatures, and increased heating costs. The solution? Invest in better insulation and energy-efficient heating solutions.

Underfloor heating is a popular choice after a knock-through. It distributes heat evenly across the space and can be more efficient than traditional radiators. If you’re already replacing flooring, it’s worth considering.

Another smart move? Double or triple glazing. If your newly opened-up space has large windows or bifold doors, upgrading your glazing can prevent heat loss and improve your home’s EPC rating—something buyers care about more than ever.

Lighting also matters. A knock-through usually increases natural light, but you’ll still need to plan for artificial lighting. LED downlights or smart lighting systems can improve energy efficiency and add a premium feel to your home.

Finally, think about ventilation. Removing a wall can change airflow, which may lead to condensation or damp issues, especially in kitchens and bathrooms. Installing an extractor fan or trickle vents can help prevent future problems.

Smart energy choices don’t just save you money—they make your home more attractive to buyers. A well-insulated, energy-efficient space is a selling point, and in today’s market, it could be the difference between a quick sale and a property that lingers on the market.

Get expert advice on structural engineer reports and planning for your wall knock-through here.