Over recent years there has been a lot of talk about the growth of alternative construction methods.
However, bricks and mortar continue to be the method of choice for most builders. With this in mind we have gone back to basics with some tips on how to ensure your walls are built to last and highlighted some examples of when things go wrong…
You can download our tips in an easy to follow checklist below:
Construction of walls
- Set out walls using securely marked profiles with reference lines and datum levels.
- Wall lengths should be checked for squareness.
- Cross check against diagonal measurements from the Architect’s plans.
- The position of openings must be anticipated to ensure correct and even bonding occurs: both horizontally and vertically.
- Avoid overstressing mortar by building rises of no more than 1.5m per day.
- Both leaves of a cavity wall should be built at the same time to avoid incorrect coursing and potential. weakening of an individual leaf (if left unsupported for any length of time).
- Where masonry is to be plastered or rendered; raked out joints approximately 15mm deep should be provided as work proceeds.
Laying bricks and blocks
- Bricks and blocks should be laid level (use the table below as a guide)
- Use a regular bond with a nominal 10mm horizontal bed joint (unless otherwise specified by the designer).
- Fill cross joints.
- Install perpend joints with a width of 7mm or more and fully bed into the mortar.
- Perpends should be kept vertically aligned as the work proceeds.
- Lay ‘frog’ bricks with ‘uppermost frog’ filled with mortar to ensure the wall is stronger and more resistant to sound transmission.
- Lay hollow blocks on shell bedding with the vertical joints filled.
- Ensure a consistent bond, especially at corners.
- Set each wall tie a minimum of 50mm into both masonry leaves.
- Keep the cavity and or insulation clear of any mortar droppings.
Guide for Horizontal and Vertical Alignment of Masonry walls
The dimensions in the table below represent the level that can be reasonably achieved for general brick and block work masonry.
Straightness in any 5m length
+ / - 10 mm
Verticality up to 2.5 m height
+ / - 10 mm
Verticality up to 7m height
+ / - 20 mm
How not to vertically align your wall
The vertical alignment of the load bearing inner leaf of block work exceeds the above recommendations.
What’s wrong with the picture below?
- The bonding is inconsistent causing vertical joints to coincide on consecutive courses.
- The correct length and type of wall ties have not been used to ensure they are properly bedded into each leaf of masonry (view the table in our article ‘How to use cavity wall ties correctly’ to see length of wall tie required for a specific cavity width).
Don’t forget to download your easy to use checklist for building masonry walls.
For more information please refer to our Technical Manual.
By Craig Ross
Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.