Topic 04 / 11
Understand damp, surface preparation and finishes.
46 questions on this topic
Search all questions →Questions and answers
A topcoat may not hide a stain if its underlying water source has not been fixed.
Repair the leak and allow the surface to dry. A suitable stain-blocking primer may be needed. If the mark keeps growing, investigate moisture rather than adding more paint.
Roller choice, paint loading, application technique and drying conditions can leave visible bands.
Use the roller and recoat interval recommended by the paint maker. Reworking an area that has started to dry can alter its colour and texture. Test the technique in a small area.
The light source, time of day, and surrounding surfaces change color perception.
View a large sample on the actual wall at different times of day. Paint sheen also affects how a colour appears. Test the actual product before deciding.
In some matte paints, friction can change the surface texture and leave shiny marks.
Check the paint’s cleaning guidance and avoid hard sponges. Choose a suitable scrub-resistance rating for frequently cleaned spaces. Touching up one spot may not fully hide an existing shiny patch.
New, absorbent plaster usually needs suitable primer and enough drying time.
Primer evens out absorption and the finish. Remove dust and check the product’s moisture and application conditions. Painting before plaster dries can cause later defects.
A smooth, glossy surface may give the new coat poor adhesion.
Clean and abrade the surface as directed, then use primer if needed. Remove loose old paint first. Test adhesion on a small area.
Paint alone will not remove all odor. Cleaning of contaminated surfaces and appropriate primer may be required.
Curtains, carpets and ventilation can also hold or spread odor. Clean residues from walls before using an appropriate stain-blocking primer and finish paint. Follow indoor ventilation guidance on the product label.
No. Find and address the moisture source and deal with the mold before repainting.
Check for leaks, condensation and inadequate airflow. Seek professional help for extensive or recurring mold. Painting a damp wall can hide continuing damage.
Condensation, leaks or poor surface preparation can impair paint adhesion.
Identify where the water comes from and inspect the window-to-wall joint. Fresh primer and paint will not last while moisture persists. Prepare the dry surface and use a suitable paint system.
High heat can make paint dry too fast, leaving visible lap marks.
Follow the temperature and humidity limits on the paint data sheet. Avoid direct sun on the work area where possible. Re-rolling an area that has begun to dry can spoil the finish.
Uneven substrate, variable absorption or roller marks become more visible in raking light.
Check surface flatness and primer coverage. Paint alone cannot hide every uneven patch; smoothing may be needed. Test the paint and roller on a sample area.
Check whether the crack is moving and what kind of joint lies beneath it.
Filler alone may only hide it temporarily. Plasterboard joints, door corners and structural movement need different repairs. If the crack grows or doors begin to stick, get a professional assessment.
Residue should be removed and the wall dried; otherwise paint may stain or fail to adhere.
Clean the wall appropriately and repair any loose areas. Choose a primer based on the paint instructions. Test adhesion in a small area first.
Many silicone sealants are not paintable; check product compatibility.
Paintable caulk and silicone are different products. Painting over old silicone usually will not give a durable finish. Choose sealant appropriate to the wet area and the planned paint system.
Grease can prevent primer and paint from adhering.
Clean, rinse and dry the wall before painting. Consider how easily the finish near the hob can be cleaned. Follow the product’s preparation instructions.
Move furniture out of the work area or cover it fully with suitable protective sheeting.
Protect floors, sockets and fixed cabinets too. Control sanding dust and provide adequate ventilation. Keep covers in place until the work is complete.
Moisture, insufficient expansion clearance or a subfloor issue may be causing it.
Check beneath the skirting board and look for nearby leaks. Pressing the raised edge down will not resolve the cause. Compare site humidity and installation with the product instructions.
Humidity changes or a problem with the click-lock joint can open gaps.
A single gap and gaps across a whole floor may have different causes. Check subfloor flatness and perimeter expansion space. Follow the flooring manufacturer’s repair guidance.
Uneven subfloor, installation clearances or movement against the underlay can cause squeaks.
Mark where the floor squeaks and check for swelling or open joints nearby. Identify the flooring system before attempting glue or screws. Ask the installer for subfloor measurements.
Moisture can weaken adhesion, cause odor and damage the substrate; check the product’s moisture limits.
A water-resistant top surface does not remove moisture beneath it. Measure substrate moisture before installing over screed or existing flooring. Resolve the moisture source before laying a new finish.
The adhesive may not have bonded fully, or the substrate may have been poorly prepared.
Check for loose tiles, cracked grout and water exposure. Record where the hollow sound occurs and keep installation documents. Regrouting alone will not restore adhesion.
Inspect substrate movement and any movement joints beneath the tiles.
Replacing grout alone will not stop movement. Cracks or junctions between different building elements beneath the tiles may be involved. Have a specialist choose the repair method.
Measure the subfloor’s strength, flatness and moisture before choosing a levelling method.
A thick underlay cannot correct every uneven floor. The levelling compound or screed must suit the substrate and flooring. Follow manufacturer tolerances and drying requirements.
Measure the door clearance against the combined thickness of the new floor covering and underlay.
Trimming the door is not the only option. Check the threshold and adjacent floor levels too. Do not cut a fire-rated or acoustic door without checking its specification.
Yes, if the chosen flooring and underlay are approved by their manufacturers for underfloor heating.
Screed moisture, surface temperature and gradual heating matter. Solid, laminate and engineered wood have different requirements. Confirm the installation manual with the fitter.
Carpet can reduce footfall noise, but the result depends on floor construction and how sound travels.
Impact noise and airborne speech call for different solutions. Review acoustic test data for the full floor and underlay system. A noise issue in an upstairs apartment may need work at its source.
Moisture absorbed by the wood or a moisture imbalance beneath it may cause cupping.
Check for leaks and high indoor humidity. Sanding immediately can cause further distortion as the boards dry. Use moisture measurements and professional advice to time the repair.
Consider the floor’s slip data, cleaning needs and whether it may get wet.
A glossy appearance alone does not determine slip performance. Check product data and a sample. Pay particular attention to bathrooms and entrances.
An uneven wall or floor, or the skirting installation, can leave a gap.
Before sealing it, check that the flooring still has the expansion space it needs. A suitable trim or removable skirting may help. Protect joints separately where water exposure is likely.
Choose flooring suited to the expected wear and keep abrasive grit off the surface.
Sand and hard particles can scratch a floor underfoot. Add pads to furniture legs and follow the maker’s cleaning guidance. No floor is entirely scratch-proof.
Heat from direct sun and installation limits can affect vinyl flooring.
Check whether the product is approved for the expected sunlight and temperature. Large glazed areas may require specific installation details. Inspect the substrate before trying to glue down lifted edges.
Confirm the shelf load, wall structure and suitable fixings before installation.
Plasterboard thickness alone does not show load capacity. Fixing into studs or planned reinforcement may be needed. Include the shelf contents in the load and have a competent installer choose the fixings.
Painting may be possible with suitable surface preparation and a coating intended for tiles.
A shower wall faces different conditions from a dry wall. Paint will not secure loose tiles. Test compatibility and expected maintenance on a small area.
Movement between wall and ceiling, or an unsuitable joint detail, may make the crack return.
Before filling, check whether it is widening or showing moisture. A suitable flexible joint may be needed. Seek assessment if the crack grows or other structural signs appear.
Draw the finished clear height alongside lighting and service requirements before deciding.
You may be able to lower only part of the ceiling. Check window tops, cabinets and doors at the proposed level. Mark the level in the room to judge how it feels.
These answers are general information; technical and safety decisions require an on-site assessment by a qualified professional.