BWIC stands for Builders Work In Connection. It covers the builder’s work needed to accommodate mechanical and electrical (M&E) services in a building: cutting holes, forming openings, chasing walls, building plinths for plant, providing fixings and making good afterwards. The main contractor normally carries out BWIC, and it is measured and priced as its own item in the bills of quantities.
Key facts
- BWIC = Builders Work In Connection (with M&E services)
- Covers holes, chases, openings, plinths, fixings, sealing and making good
- Normally carried out by the main contractor, not the M&E subcontractor
- Measured under NRM2 work section 41 in UK bills of quantities
- Early cost plans often allow 1% to 5% of the M&E package value for BWIC
What does BWIC mean in construction?
BWIC is short for Builders Work In Connection, sometimes written out in full as “builder’s work in connection with mechanical and electrical services”. Every building needs holes for pipes, openings for ductwork, chases for cables and solid bases for plant. Adapting the building fabric like this is the builder’s job, not the M&E installer’s, and BWIC is the label the industry gives that work.
You will meet the term in tender documents, bills of quantities, M&E specifications and on drawings1. In UK bills of quantities it has its own work section: NRM2 section 41, builder’s work in connection with mechanical, electrical and transportation installations. Under the older SMM7 rules the equivalent was section P31, holes, chases, covers and supports for services2.
Watch out for wrong definitions floating about online. BWIC does not mean “best work in construction”, “built work in charge” or “by others”. If a UK construction document says BWIC, it means builders work in connection, full stop.
The term comes from commercial contracting, but the same idea applies on a house extension or rewire. The electrician wants chases cut and the plumber wants holes through joists, and someone has to do that work and make good afterwards. On small domestic jobs it is often the same builder or the individual trades, but the work is still builders work in connection, whether or not anyone writes BWIC on a document.
Construction drawings are full of abbreviations like this. If you have also spotted SVP on a plan, our guide to SVP meaning in construction explains that one.
What are typical BWIC examples?
BWIC covers dozens of small jobs, but they all follow the same pattern: adapt the building so the services fit, then put the finishes back. The table below lists the items you will see most often on a BWIC schedule.
| BWIC item | What it involves | Typical trade |
|---|---|---|
| Holes and penetrations | Cutting or forming holes through walls, floors and roofs for pipes, ducts and cables | Builder / main contractor |
| Openings | Forming larger openings for ductwork, risers, grilles and access panels, with lintels where needed | Main contractor |
| Chases | Cutting channels in blockwork, brick or plaster for cables and pipework | Builder (M&E trade marks out) |
| Plinths and bases | Concrete bases for boilers, tanks, chillers, air handling units and switchgear | Main contractor |
| Fixings and supports | Bearers, brackets, noggins and framing for equipment, cable tray and pipe runs | Main contractor / carpenter |
| Trenches and ducts | Excavating and ducting for incoming gas, water, electricity and drainage | Groundworker |
| Sealing penetrations | Sealing around pipes and cables where they pass through walls and floors, including fire-rated sealing on compartment lines | Main contractor / firestopping specialist |
| Making good | Filling chases and patching plaster and finishes once services are installed and tested | Plasterer / decorator |
Note making good at the bottom of that list. Once the electrician and plumber have finished, somebody has to fill the chases and patch the walls, and on most jobs that is a reliable local plasterer working behind the M&E trades.
What are BWIC drawings?
BWIC drawings, also called builders work drawings, tell the builder exactly what holes, openings, chases and plinths the M&E installation needs, with sizes, levels and setting-out dimensions. The M&E contractor or building services engineer produces them, usually one drawing per floor or per service.
A good BWIC drawing uses a simple legend. Each symbol tells the builder the type of penetration, its size, and whether it needs fire-rated sealing afterwards. Ductwork, pipework and electrical containment are often shown in different colours so clashes stand out at a glance.
Timing is everything. An opening formed in blockwork as the wall goes up costs little more than the lintel over it. The same opening diamond-drilled through a finished, decorated wall costs many times more and holds up two trades while it happens. BWIC drawings are meant to be issued and checked before each phase of the build, not after, so openings are formed rather than cut.
On site the usual sequence is: the M&E contractor marks out from the BWIC drawings, the builder cuts or forms the work, the services go in, the penetrations are sealed, and the plasterer makes good. Miss a step and the snagging list grows fast.
Who pays for BWIC?
The client pays for BWIC in the end, through the main contract price. The practical question is where it is priced and who carries the risk if it gets missed.
On a traditional contract, BWIC is measured in the bills of quantities under NRM2 section 41 and priced by the main contractor. Where the M&E design is not complete at tender stage, it often goes in as a provisional sum and is firmed up once the builders work drawings are issued.
M&E subcontract packages vary. Some include the subcontractor’s own builder’s work, most exclude it and leave it with the main contractor. The subcontract documents should say which, in plain words.
Disputes almost always come from gaps in that paperwork. The M&E subcontractor assumes the builder will cut and seal every hole. The builder has priced only what was shown at tender. Months later somebody has to pay for 200 unpriced penetrations. The fix is boring but simple: define BWIC clearly in the contract documents, state who cuts, who seals and who makes good, and record anything added after tender as a variation at the time, not at final account.
How much does BWIC cost?
At early cost-plan stage, quantity surveyors usually allow a percentage of the M&E package value for BWIC, commonly between 1% and 5%. A services-heavy building such as a hospital or laboratory sits at the top of that range. A simple warehouse sits at the bottom.
Once BWIC drawings exist, the work can be measured properly item by item. Rates depend on the substrate (drilling reinforced concrete costs far more than blockwork), access, whether fire-rated sealing is specified, and the standard of making good required.
Late BWIC is the expensive kind. Every hole that has to be diamond-drilled after the finishes are on carries the cost of the cutting, the dust protection, and the plasterer and decorator to put the wall back. Getting the builders work drawings out early is the cheapest cost control there is.
What is the difference between BWIC and builders work?
Builders work is the general term for any building work carried out by the builder. BWIC is a specific slice of it: only the builder’s work that exists to accommodate the services. Digging footings is builders work. Cutting a 110mm hole through a wall for a soil pipe is BWIC.
BWIC is also different from attendance. General attendance covers the facilities a main contractor provides for all subcontractors, such as welfare, temporary power, lighting, water and space for storage. Special attendance covers extras for one particular trade, like scaffolding, hardstanding or help with unloading heavy plant.
The distinction matters when you price a package, because BWIC is physical work on the building fabric and is measured item by item, while attendance is a facility and is usually priced as an allowance. Mix the two up at tender and the money will not add up on site.
Why does BWIC matter in project management?
BWIC sits at the joint between the building trades and the services trades, which is exactly where projects go wrong. Late or missing builders work information leads to holes cut in the wrong place, structural members drilled without an engineer’s approval, and trades standing idle while they wait on each other.
Three habits keep it under control. First, get BWIC drawings issued and reviewed before each construction phase, and check them against the structural drawings for clashes. Second, agree in writing who cuts, who seals and who makes good, both in the main contract and in every M&E subcontract. Third, record every extra penetration as it happens.
Done well, BWIC is invisible. The openings are where the ductwork needs them, the fire compartments stay intact, and the plasterer arrives to make good once, not five times. Done badly, it is a running argument that shows up in the final account and in the cracks along every badly filled chase.
A simple checklist before the M&E trades start on site:
- BWIC drawings issued, current revision, checked against the structural drawings
- Contract documents state who cuts, who seals and who makes good
- Fire compartment lines identified so every penetration through them gets rated sealing
- Structural engineer’s approval in writing for any holes through beams, joists or slabs
- A plasterer booked for making good, with the finish standard agreed up front
- A running record kept of penetrations added after tender
How does BWIC affect plastering work?
Plasterers meet BWIC on nearly every job. Chases for new cables and pipes get cut straight through existing plaster, and once the services are in, those chases need filling and skimming flush so you would never know they were there.
Making good after M&E work is skilled work in its own right. Fill a deep chase in one go and it will shrink and crack along its length within weeks. The proper method is bonding coat in layers, scrim or mesh over wide chases and around boxes, then a skim coat feathered into the surrounding wall.
For budgeting, small patching and chase filling is usually charged by the half day or day rather than per metre. Our UK plastering price guide covers current day rates and skimming costs.
If you have electrical or plumbing work planned and want the walls put right afterwards, talk to our plasterers in Kent for a quote on chasing and making good.
Frequently asked questions
What does BWIC mean in construction?
BWIC means Builders Work In Connection. It is the builder’s work needed to accommodate mechanical and electrical services: cutting holes, forming openings, chasing walls, building plant bases, providing fixings and making good afterwards. The main contractor normally carries it out, and it is priced as its own section in the bills of quantities.
What are examples of BWIC?
Typical BWIC examples are holes through walls and floors for pipes and cables, openings for ductwork and risers, chases for wiring, concrete plinths for boilers and tanks, fixings for cable tray and pipework, trenches for incoming services, sealing around penetrations, and making good plaster and finishes once the services are installed.
Who pays for BWIC?
The client pays for BWIC through the main contract price. On traditional contracts it is measured in the bills of quantities under NRM2 section 41 and priced by the main contractor, sometimes as a provisional sum until the M&E design is complete. Disputes happen when subcontracts do not state who cuts, seals and makes good, so define it clearly at tender stage.
What are BWIC drawings?
BWIC drawings are builders work drawings produced by the M&E contractor or building services engineer. They mark the position and size of every hole, opening, chase and plinth the builder must provide, usually with a legend for each service. They should be issued before each construction phase so openings can be formed as the building goes up rather than cut afterwards.
What is the difference between BWIC and builders work?
Builders work covers any general building work. BWIC covers only the builder’s work in connection with services, such as holes, chases and plant bases. Digging footings is builders work; cutting a hole through a wall for a soil pipe is BWIC. It is measured separately in bills of quantities, under NRM2 section 41 in the UK.
Is BWIC the same as attendance?
No. Attendance covers facilities and support the main contractor gives subcontractors, such as welfare, temporary power, lighting, storage and scaffolding. BWIC is physical building work carried out to accommodate the services, like cutting holes and forming bases. The two are measured and priced separately, so keep them apart when pricing a package.