How a building expansion joint is installed
We make the joint and our own crews fit it, so one company answers for both. This is the sequence our method statements set out for a new building, and the points a consultant should check in any installer’s method statement before work starts.
Three checks that decide whether the joint fits
Structural gap against the submittal
The gap as built is measured and compared with the gap the system was chosen for. A joint is rated for a gap range; a gap outside it is a design question, not a site adjustment.
Blockout width and depth
The recess left in the slab or wall must match the system’s blockout from its data sheet. Too narrow and the frames do not seat; too wide and the edge has to be built back before fixing.
What goes in the gap first
A fire barrier and a waterproofing membrane, where the joint needs them, are installed in the structural gap before the cover system, each to its own method statement.
The installation, step by step
The order below is common to our floor, wall and roof systems. Component names, fixings and torques differ by system and are given in that system’s method statement.
- Prepare the substrateThe floor or wall is flat, level and free of debris. Components come out of their packaging without marking the exposed faces.
- Form a rebate where the finish zone is too thinThe rebate is cut square and never wider than the blockout. Its depth is the full height of the profile plus 5–10 mm for tolerance.
- Lay the levelling bedA high-strength mortar of at least 40 N/mm², continuous along the whole run, at least as wide as the blockout, and set so that bed plus frame height brings the frame to finished floor level. It cures fully before any drilling.
- Set out and drillThe frames are laid at the blockout width, the holes marked through the frames, and the frames lifted away for drilling. Where a membrane runs under the frames, each hole takes a resin anchor so the membrane stays sealed.
- Fix the frames and fit the coverFrames are fixed with the anchors and torque the method statement gives; plates, gaskets or seals are fitted in the order it shows. Locating dowels align each 3 m length with the next.
- Join and finish the lengthsLengths are cut square with a metal chop saw and an aluminium-cutting blade at 12,000 rpm or more, so the ends meet flush. Intersections and corners follow their own detail.
- Backfill and cleanThe blockout is backfilled and the floor finish laid level with the top of the frame. Exposed metal is cleaned with a non-solvent cleaner.
- Protect until handoverSite traffic is kept off the joint, and the protective tape stays on the visible face until the finishes around it are complete.
For the blockout and fixing detail in more depth, see Blockout, rebate and fixing.
What an installation method statement should state
Whoever installs the joint, these are the items to see in writing before work starts.
- The system and its rating: product reference, the gap range it is rated for, and the surveyed gap it is going into.
- Blockout and rebate: width, depth and tolerance, and who forms them.
- Levelling bed: the mortar, its strength, its minimum depth, and the cure before drilling.
- Fixings: anchor type, size, spacing and torque, and the resin used where a membrane is crossed.
- Fire and water: whether a fire barrier and a membrane go in the gap, in what order, and who owns the lap to the structural waterproofing either side.
- Joints between lengths: alignment, cutting and how corners and intersections are made.
- Protection and handover: how the joint is protected from site traffic, and the cleaning and maintenance instructions handed over with it.
Our method statements cover the MegAtec 300, 310, 340, 360, 370 and 610, the SeismAtec 450 and the FlexAtec 1000 and 1200. Ask for the one for your system with the data sheet.
Cleaning and maintenance
Clean the joint with a mild detergent. Avoid abrasive cleaning: over time it damages the surface of the profile. A joint that starts to rattle, lift or leak is telling you something early; repair and replacement covers what to do then.
Send the drawings. We size and install the joints.
We return a joint schedule with the gap, the system and the movement class for each location, then supply and install it with our own crews.