Cement and mortar
Alkaline, porous and carbonate-bearing — which means acid dissolves it, and it damages an aluminium finish if allowed to dry on one.
What not to do
Hydrochloric acid is unsafe on Cement and mortar
Unsafe
Do not do this. The risk is established, and it is described below.
The joint dissolves faster than the deposit does, and joints do not grow back.
Why we say this
Supported
Cement-based materials are carbonate-bearing and are attacked by the same reaction. Recorded as interpretation rather than direct support because the manufacturer's sentence is about stone rather than about mortar, and this catalogue does not put words into it.
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That acid washing is material-dependent and that limestones and marbles are dissolved by hydrochloric acid. (cleaninghq's interpretation of what it says)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Last reviewed by a person on .
Quicklime requires the precaution Cement and mortar
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
- Ventilate the area
- Keep away from children and pets
Why we say this
Strongly supported
Recorded as a precaution edge rather than a damage one because the hazard is to the person rather than to the substrate. Included at all because limewashing recurs in restoration and traditional-building contexts.
Sources
Right to Know Hazardous Substance Fact Sheet: Calcium Oxide (RTK 0325)
New Jersey Department of Health, 2003 · Government or regulator
Relied on for: That contact can severely irritate and burn the eyes and skin, that inhalation irritates the lungs and higher exposure may cause pulmonary oedema, and that long-term exposure can perforate the nasal septum and crack the skin. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' block and the hazard summary. Supports the claim as stated. Gives the historical record a substance with a regulator behind it, and supplies the occupational-injury detail that keeps a history of cleaning from becoming nostalgia.
Last reviewed by a person on .
In detail
Cement-based materials — mortar joints, render, concrete paving, screed and the grout between tiles — share three properties that decide their care. They are strongly alkaline when fresh and stay mildly so. They are porous, so oils and coloured liquids are absorbed rather than resting on the surface. And they contain carbonate compounds, which is why acid attacks them: a descaler, a brick acid or a strong bathroom cleaner used on tiled walls dissolves the joint faster than it dissolves the deposit, and the joint does not grow back. The alkalinity is a hazard in the other direction too. A standards body warns that alkaline materials such as cement and mortar quickly corrode anodic coatings if allowed to dry on the metal, which is how new aluminium windows are damaged during building work. Two further points. Pressure washing removes jointing material if the lance is aimed down rather than held at a shallow angle, and empty joints are detrimental to a pavement's performance. And efflorescence is not dirt: the stone trade's instruction is to dust-mop or vacuum it and avoid water, which dissolves the salts and carries them back in.
Properties
Sensitivity
- Acids
- Recorded
- Alkalis
- Not applicable
- Chlorine bleach
- Not known
- Abrasion
- Recorded
- Porous
- Recorded
“Not known” means CleaningHQ has not established this, not that the material is unaffected.
What works
Detergent is safe on, in specific conditions, Cement and mortar
Safe only in specific conditions
This is only appropriate within specific limits. Outside those limits, CleaningHQ makes no claim.
Only within these limits:
- Structurally sound surfaces only
- Hot water with household detergent and a stiff brush; the aim is physical removal, not killing
- Dry completely within 24 to 48 hours
- Correct the moisture problem first
Named by a state health department among the materials that can be cleaned rather than discarded when mouldy: hard plastic, solid wood, concrete, metal and glass.
Precautions
- Ventilate the area
- Wear gloves
Why we say this
Supported
A regulator's own material list, carried without extension. Materials it does not name are not cleared by this edge.
Sources
Minnesota Department of Health · Government or regulator
Relied on for: That concrete and mortar among other hard materials can be cleaned if structurally sound, using a stiff brush with hot water and household detergent to remove the physical mould growth. (states this directly)
Verification: a person has read the passage relied on.
Read on — The cleanup steps, the bleach step, and the salvageable-materials section. Page last updated 19 February 2026. Supports the claim as stated.
United States Environmental Protection Agency (EPA) · Government or regulator
Relied on for: That mould is scrubbed off hard surfaces with detergent and water and dried completely. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Mold Cleanup' section and the 'Tips and Techniques' list. Supports a narrower statement — our claim was reduced. CleaningHQ had been prepared to attribute a bleach position to the EPA in either direction, which the page does not support. The catalogue now states only what the agency states — detergent and water, dry completely, fix the moisture — and the widespread belief that mould requires bleach is handled as an assessed claim resting on the absence of any authority recommending it, not as an EPA prohibition.
Last reviewed by a person on .
Why
- Cement and mortar is explained by Etching versus staining
- Cement and mortar is explained by Porous and non-porous surfaces
Related
- Cement and mortar is commonly affected by Moss and lichen
- Cement and mortar is commonly affected by Algae
- Cement and mortar is commonly affected by Oil and grease on textile
Hacks and claims involving this
- Jet-washing the patio every spring Supported
Sources for this page
Sources
AAMA 609 & 610-02: Cleaning and Maintenance Guide for Architecturally Finished Aluminum
American Architectural Manufacturers Association (AAMA), 2002 · Standards body
Relied on for: That alkaline materials such as cement and mortar will quickly corrode anodic coatings if allowed to dry on the metal. (states this directly)
Verification: a person has read the passage relied on.
Read on — Read in full. Sections 3 General, 4.1 light surface soil, 4.3 organic coatings, and 5 Cleaning Precautions. Supports the claim as stated.
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That the lance must not be directed down onto paving because that costs jointing material, that it should be held at a shallow angle not greater than 30 degrees, and that joints should be inspected afterwards because empty joints are detrimental to pavement performance. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Care & Cleaning of Natural Stone
Natural Stone Institute · Trade or professional body
Relied on for: That efflorescence is dust-mopped or vacuumed and that water is avoided. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 read all nine sections. Earlier sprints had read three: the siliceous-versus-calcareous classification, cleaning products, and sealing. Supports a wider statement — our claim was widened. Three sections of nine had been read and the source treated as complete. The unread six carry the whole preventive programme - coasters, trivets, non-treated dry mopping, slip-resistant mats, worn vacuum wheels, blot-don't-wipe - none of which the register held. They also answer a priority-1 row reading 'no route answers this yet': the authority's position on etch marks is that they are not a cleaning problem and need professional re-polishing. Two oddities are worth the record: dry 0000 steel wool is permitted on water rings, and efflorescence is removed dry because water makes it worse.
Last reviewed by a person on .