Render cracking as it dries

Question

We had the back of the house rendered last week and fine cracks have appeared across it as it has dried. The renderer says this is normal and will be covered by the top coat. Is that right?

Tom · Answer

Sounds like the first coat ( base coat) has been applied. It is possible that it has dried to fast in direct sun on a warm day. Another reason could be you have had other heavy building work done shortly after it has dried causing micro movements before the base coat has fully cured. If this is the case you will have nothing to worry about. other than that it is unusual for it to crack so soon. Hope this helps

Linas · Answer

Dependent how big craks, mabe its ok put a silicone on the craks and painting with white prime all walls before put silicone top coat or maybe renderer gave to much bace coat, if to mach bace coate need put one more thin coat bace coate

Sam · Answer

Sometimes it can be caused by movement driving too fast. Longs the wall not hollow should be fine when pained

Mike · Answer

The cracks need looking atvand repairing before any top coat is applied 
These are shrinkage cracks

Benjamin · Answer

Yes — fine, hairline cracks appearing as the render dries are normal and are usually covered and sealed by the top coat, as long as they are genuinely shrinkage/crazing cracks.

What’s normal- 
Fine “crazing” or shrinkage cracks happen when render cures and loses moisture.
They are typically:
Very thin (often <1 mm)
Spread across the surface like a faint map pattern
Not following a straight line or brick pattern
Not getting wider over time

These are cosmetic only and are commonly fixed once the top coat goes on. Silicone or monocouche top coats are specifically designed to bridge and hide these hairline cracks.

What’s not normal If the cracks are:
Straight vertical/diagonal lines
Following the brick/block pattern underneath
Radiating from window/door corners
Wider than 1–2 mm
Growing over days/weeks

…then that can indicate movement or poor reinforcement, not simple drying shrinkage. These types won’t be solved by a top coat alone.

Quick checks you can do
Tap the render: if it sounds hollow, that can indicate poor bonding.
Look at the crack pattern: random hairlines = normal; straight lines = investigate.
Check width: anything wider than a hairline needs attention.

Bottom line for your situation based on what you’ve described — fine cracks appearing across the surface after drying — this matches normal shrinkage/crazing, and your renderer is correct that the top coat will cover them.

James · Answer

If its a thin coat render system it should be fully meshed before top coat applied and would be unusual to have cracks of any substance! If it was hot on the day of applied could of dried to fast this will cause cracking

Jwan · Answer

The renderer is generally correct. Fine, surface-level cracks (hairline shrinkage cracks) often occur as the base coat cures and dries, and a properly applied flexible top coat will fill and seal them.

Glyn · Answer

No that's probably  blown, and the top coat will do exactly the same.

Gene · Answer

Tap walls with coin or something and if sounds hollow anywhere then it’s blown and in time will fall off

Render cracking as it dries

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