Rain after building an oven is a good time to check the water path, but not for randomly fixing every joint. A darker spot may be wet, and a detached section requires determining the cause. Examine the cold structure and note how much time has passed since making the connections.
The condition of the mortar depends on the stage of work
Outdoor Oven Cement is a hydraulically setting mortar, also intended for compatible outdoor applications. The resistance of the finished joint does not mean that a freshly built wall can be left without the required protection. Separate the conditions of application, curing, and later use.
Check the instructions for the batch used. If rain fell during fresh work, note the time and extent of wetting. Do not confirm quality solely by surface touch; the preparation and support of the entire joint also matter.
Look for the cause at the edges
Examine the top ends of the wall, the base, the entrance, and contacts with metal. Water can reach the joint from the neighboring layer. Sealing only the visible point will not solve the problem if precipitation continues to flow behind the covering.
Where material has chipped away, check the stability of the bricks and the size of the void. Heatproof Screed has applications in appropriate larger fillings, but its selection does not replace the assessment of the cause of the damage. Do not apply a thick patch on a movable or loose substrate.
Record the repair and observe
Prepare the area according to the chosen material. Maintain the specified setting, protection, and drying conditions before reheating the oven. Subsequent inspection should include the repaired joint and the point allowing water to enter.
Take photos before and after the repair from a similar location. If the void recurs next to the same brick, reassess support and the behaviour of the structure. Another surface filling without recognizing movement can only delay the next repair.