Before choosing tile, vinyl, timber or laminate, make sure the base is dry, sound and flat enough for the flooring system you intend to install. Self-levelling compound deals with minor irregularities across a continuous area; manual levelling is better for adjusting levels, local hollows, thresholds and transitions. Leaving this decision until late in the job often leads to rubbing doors, open joints, creaking floors or unexpected material use.
In a Lisbon flat, the right approach starts by measuring the existing slab or screed, checking for moisture and setting the finished level at doors, kitchens and bathrooms.
Contents
- What should be decided before ordering flooring
- When self-levelling compound is the right choice
- When manual levelling is the safer option
- How to check the base in six simple steps
- Mistakes that make flooring installation more expensive
- When to stop and call a professional
What should be decided before ordering flooring
Floor preparation is not an invisible finishing task to solve at the end. It establishes the finished floor level and affects skirting boards, internal doors, kitchen units, shower trays and balcony thresholds. Mark a level reference in every room and compare it with the existing openings.
- Confirm where the new floor must meet a different finish.
- Measure clearance below doors and available height beside fixed cabinetry.
- Locate cracks, hollow areas, adhesive residue and old patches.
- Decide whether there will be acoustic underlay, insulation or underfloor heating, because every layer adds height.
Where work affects building-envelope elements with a significant impact on energy performance, applicable requirements must be considered whenever the solution is technically and functionally possible; this is set out in the Portuguese building energy-performance regime. For guidance on measures that improve thermal comfort and efficient energy use, see the ADENE energy-efficiency resources. For a straightforward renovation, that becomes a practical question: does the new build-up improve comfort without creating moisture, level changes or unusable doors?
When self-levelling compound is the right choice
Self-levelling compound is a fluid mortar designed to create an even surface, mainly where small undulations are spread across a room. It works well before glued vinyl, glued engineered timber or other finishes that readily show defects in the substrate. It can also help over an older screed after stable cracks have been repaired and residues that would prevent adhesion have been removed.
It should not be treated as an automatic way to hide every defect. If an area moves, a crack is active, rising damp is present or there is a major level difference, pouring material over it only postpones the problem. The base needs to be clean, firm and prepared with the compatible primer specified for the system.
There is also a practical limit: mixed material has a short working time and needs to be poured continuously. In an occupied home, plan access, protect doorways and do not interrupt the application halfway across the room.
| Condition of the base | Usually suitable approach | Check before proceeding |
|---|---|---|
| Minor undulations across a large area | Self-levelling compound | Adhesion, cleanliness, primer and intended thickness |
| Local hollows or transitions | Manual levelling | Door levels, thresholds and junctions with other floors |
| Loose base, significant crack or moisture | Diagnosis and repair before levelling | Cause of the defect and compatibility of the repair |
| Level changes across several rooms | A defined floor build-up in the design | Finished heights, loads and edge details |
When manual levelling is the safer option
A mortar applied with a straightedge offers more control where geometry needs to be built or restored: beside a threshold, across a transition between hallway and bedroom, where a partition has been removed or over a plumbing repair. It allows deliberate falls and the correction of a small area without raising the whole room.
It does, however, require closer execution control. The straightedge must bear on defined references, and the thickness must follow the chosen product’s limits. A layer that is too thin can lack strength; one applied too thickly, outside the intended system, may shrink, crack or take too long to dry.
In bathrooms, do not confuse levelling with waterproofing. The base may need correction first, but waterproofing and drain junctions belong to their own sequence. If you are rebuilding a shower, read how to compare liquid and sheet membranes before closing the floor build-up.
How to check the base in six simple steps
- Remove anything that does not adhere. Scrape away loose adhesive, paint, plaster and old flooring residue.
- Test firmness. An area that breaks up when scratched or sounds hollow needs repair, not another layer over it.
- Look for moisture. Staining, salts or persistent odour should be resolved before sealing the base.
- Measure with a long straightedge. Mark high and low points; do not judge flatness by eye.
- Draw the finished levels. Include the flooring, adhesive, underlay and skirting.
- Check compatibility. Primer, mortar, adhesive and floor finish should work as one system.
If the work affects structure, building services or other specialist disciplines, it is no longer simply a finish decision. Lisbon City Council lists thermal performance, stability and water-and-drainage networks among the specialist designs that may be required; see its information on specialist design projects before assuming that levelling and flooring are all that is involved.
Mistakes that make flooring installation more expensive
The most frequent mistake is selecting the levelling method after the flooring has been purchased. Floating flooring may tolerate some variation, but it will not correct an unstable base; glued finishes demand even greater accuracy. Another common error is raising only one room, then discovering that the entrance door or washing machine no longer has enough clearance.
- Applying self-levelling compound without primer or over dust.
- Covering a crack without finding out whether it is still moving.
- Using thick underlay to compensate for holes and undulations.
- Installing the floor before the mortar has reached its specified drying conditions.
- Closing skirting boards and units without allowing for required technical edge details.
Where the existing base is an old screed, also compare the implications of a replacement layer in our article on dry and wet screed in renovation. The best choice depends on available height, the substrate and the construction sequence, not only on apparent speed.
When to stop and call a professional
Do not proceed with cosmetic levelling where the floor is progressively sinking, cracks are wide or recurring, there are signs of water beneath the finish, timber is decayed, rust is visible or adjacent rooms have an abrupt level difference. These signs may involve the slab, a leak or an earlier alteration that was never properly resolved.
In Lisbon, internal work that does not affect structural stability, façades, roofs or other regulated elements may follow a simpler route; that does not make every demolition, opening or load alteration exempt from control. Check the specific case through the City Council information on building works subject to prior communication.
The useful next step is to ask for the work proposal to separate substrate preparation, primers, levelling, drying times, flooring installation and edge finishes. That makes it easier to compare options without mistaking a properly prepared base for an unexpected extra.
Key takeaways
- Set finished floor levels before selecting the levelling method or flooring.
- Use self-levelling compound for small continuous irregularities; use manual levelling for local corrections and transitions.
- Moisture, loose substrate or significant cracking require diagnosis before any new layer is applied.
- Ask for preparation, materials, drying and finishing details to be shown separately in the quote.
Planning new flooring for a Lisbon home or flat? Obra Lisboa can help turn the chosen solution into a clear work scope, with layers, edge details and preparation work defined before appointment.
Sources and further reading
- ADENE energy-efficiency resources
- Portuguese building energy-performance regime
- specialist design projects
- building works subject to prior communication
Editorial image; it does not depict an Obra Lisboa project.
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