Building components · Frame Members
Splice Connection
Explains the splice as a position where continuity has to be remade along a member, distinct from where a member is supported or where several members meet.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a splice is
Structural members arrive in lengths that can be fabricated, transported and lifted. Where a member has to be longer than that, it is joined end to end at a splice: plates or an end plate bolted or welded across the joint so that the member continues past it as a single member rather than as a pair meeting.
What makes it a position rather than a detail is that the joint has to reproduce whatever the member was doing at that point along its length — being pulled, being pushed, being bent, or all of those at once. That is why where a splice sits is a design decision rather than a delivery one: it is commonly placed where the forces along the member are at their lowest, and moving it moves what it has to carry.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a structural bearing. A bearing is where one member is supported by another and its load passes out of the member and into its support; a splice is where a member continues into itself and the load passes along it, so nothing is being supported at a splice at all.
- It is not a gusset connection. A gusset joins several different members converging at a node at angles to each other; a splice joins two lengths of one member running in the same line, and there is only ever one member at a splice.
- It is not a movement joint. A movement joint is made deliberately discontinuous so that the structure either side can move independently; a splice exists to remove a discontinuity and make a member behave as though the joint were not there.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- splice
- site splice
- butt splice
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Where along the member it sits relative to the forces at that point, which is what the joint has to be arranged for.
- Whether it is designed to carry the member's full capacity or only the forces present at that position, since those are different requirements that produce different joints.
- The fit-up of the two ends and the arrangement of bolts or welds across them.
- Access to make the connection and, afterwards, to inspect it, since a spliced joint that cannot be reached cannot be checked.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Everything the member carries at that point passes through the splice, so the joint is the member at that position rather than an addition to it.
Two fabricated lengths have to meet on site as drawn, and the splice is commonly where fabrication tolerance and erection tolerance are resolved against each other.
A splice is placed partly so that the two pieces either side of it can be delivered and lifted, which makes it one of the few connection positions where structural and logistical reasoning meet.
What was made at a site splice, and what was inspected, is worth having recorded — it is a joint that is commonly concealed soon after it is completed.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Clarifications
Commonly misunderstood
- That a splice is a weak point by definition. It is arranged to carry what the member carries at that position, and its position along the member is chosen for that reason.
- That a splice can be moved on site to suit delivery, access or a clash. Where it sits is tied to the distribution of force along the member, which is a design matter rather than a site one.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- Why is the splice at this position along the member?
- Is this joint arranged to carry the member's full capacity or the forces present here?
- Was the connection made as drawn, and what record exists of it?
- Will the splice remain accessible for inspection once the works around it are complete?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- This entry describes a connection position. It states no bolt arrangement, plate size, weld specification, capacity, spacing or fire rating, and none can be inferred from it.
- Where a splice sits along a member and what it is arranged to carry are settled together by qualified design, so a splice introduced or relocated on site is a defect because the forces it has to reproduce are not the ones it was drawn for.
Structural Frame Members
The columns, beams, joists, rafters, plates and bracing that make up a load-carrying frame, identified by the position each occupies.
Browse all frame members entries →