Substrate responsibility
Specifying who is responsible for substrate preparation before a liquid screed pour
Disputes over substrate readiness are common where a specification does not clearly state who is responsible for preparing the base before the screeding contractor arrives.
One of the most frequent sources of friction on a screed contract is a disagreement over whether the substrate was in a suitable condition when the screeding contractor arrived, and this usually traces back to a specification that did not clearly assign responsibility for preparation in the first place.
Substrate preparation can include removal of debris and laitance, dealing with existing floor finishes or adhesive residues, checking and treating cracks or joints, and confirming the base is dry enough or otherwise ready for a membrane or bonding agent to be applied.
A specification that states explicitly which party carries out and pays for each preparation task, and what condition the substrate must be in before the screeding contractor's programme starts, removes much of the ambiguity that otherwise surfaces as a dispute mid-contract.
Substrate preparation responsibilities — the points that decide it
- State explicitly whether substrate preparation, such as shot-blasting, scarifying or scabbling, is included within the screeding contractor's scope or is a separate preceding trade.
- Define the condition the substrate must be in before the screeding contractor's programme start date, including cleanliness, level tolerance and dryness.
- Clarify who is responsible for identifying and treating existing cracks, joints or damaged areas in the base before screeding.
- Set out who removes existing floor finishes, adhesive residues or coverings, since this is frequently assumed by one party to be someone else's job.
- Specify who checks and confirms any damp proof membrane is intact and correctly positioned before screeding proceeds.
- Include a mechanism for recording substrate condition, such as a joint inspection or photographic record, before the screeding contractor commences work.
- Address what happens if the substrate is found not to meet the agreed condition on the day, including who bears any resulting delay cost.
Why this is worth stating explicitly
Preparation tasks like removing laitance, dealing with residues, or checking a damp proof membrane are often assumed to be self-evidently someone's job, but different parties on the same project can reasonably read the same silence differently. A main contractor may assume the screeding specialist includes preparation as standard practice, while the specialist may have priced only the screed application itself.
This gap tends to surface at the worst possible moment, when the screeding crew is mobilised and ready to pour but finds the substrate is not in the condition assumed, leading to either a delayed start or a rushed, inadequate preparation carried out under time pressure.
Setting a clear condition and inspection point
A specification that defines the substrate condition required before the screeding programme starts, such as free of debris, laitance removed to expose sound concrete, cracks treated, and any damp proof membrane confirmed intact, gives both parties an objective standard to check against rather than a subjective judgement made on the day.
Building in a short joint inspection, ideally recorded with photographs or a signed checklist, before the screeding contractor commences gives a documented record of the condition handed over, which is useful if a dispute arises later about whether preparation was adequate.
Allocating risk for late-discovered problems
Even with a clear specification, substrate problems can be discovered only once preparation work is underway, such as an unexpectedly friable slab surface or unrecorded ducting beneath the floor. The specification should ideally anticipate this by setting out how additional preparation work discovered on the day will be instructed, valued and programmed, rather than leaving this to be negotiated under time pressure once work has already stopped.
Who protects the floor once preparation and pouring are both done
Responsibility does not end once the screed cures; the party who handed over a clean substrate at the start is often the same one expected to keep other trades off the new surface afterwards, so naming that in the same clause avoids a second dispute replacing the first once the floor is poured.
Unclear who covers substrate preparation on your project?
We can help draft a clear preparation scope so responsibilities are agreed before work starts.
Or call our landline on 01392 237700
In short
Disputes over substrate readiness are common where a specification does not clearly state who is responsible for preparing the base before the screeding contractor arrives.
Substrate preparation responsibilities — your questions
Unclear who covers substrate preparation on your project?
We can help draft a clear preparation scope so responsibilities are agreed before work starts.