Roundtower Harbour Mortar

Roundtower Harbour Mortar

Fast setting and durable mortar for aggressive marine environments.

This product is not available to buy online. Please contact us for pricing and more information.

€ 0.00 EUR
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Delivery Information

Unless otherwise specified all products within Ireland should be delivered within 2-3 working days. Please contact us for delivery options outside of Ireland or if you wish to ship to Northern Ireland.

Our stock is primarily shipped by Fastway or via the pallet network depending on the total weight of the order. The delivery method will be automatically assigned and priced at checkout. All delivery prices include VAT.

Main Purpose

Fast setting and durable mortar for aggressive marine environments.


After mixing, a bag will produce approximately 12 litres of mortar, sufficient to lay approximately 20 standard house bricks with a uniform 10mm joint.

Similar to the Marine Mortar but completely waterproof and resistant to sulphates, Roundtower Harbour Mix provides a fast setting, extremely durable mortar for the most aggressive marine environments. Both Marine Mix and Harbour Mix will set underwater.

Harbour mortar is a quick setting, dry ready mixed mortar made using Prompt, a Natural Cement that has been used throughout Europe since the mid-19th century and found exclusively in the French Alps close to Grenoble. Prompt (PNC) having demonstrated excellent characteristics during long term testing (submerged in La Rochelle Harbour for more than 50 years) has been deemed suitable for work at sea and meets French Standards for sea-water setting cements. While it can be used in numerous applications where a quick set is required, we have designed it for use around more aggressive marine environments, where a faster set is desirable working within the tidal window, to help prevent wash out or tidal scouring.

It is supplied as a dry ready to use (add water) Factory blended mortar using kiln dried coarse sand and Prompt, combined with carefully selected additives to provide a longer open time for the mortar. With reduced shrinkage and a high degree of durability whilst maintaining good workability, along with many of the virtues of an eminently hydraulic lime mortar.

Setting Time & Use:

The setting time of Harbour Mortar is climate dependant and will be somewhat variable with a safe working time in the order of 30 minutes; which could quite easily be closer to 60 minutes in colder weather and possibly

AFTER setting starts: Do not add water, re-mix or temper in any way: Setting only occurs once (risk of breaking the set)