Scratch Coat

How Long Does it Take for Scratch Coat to Dry?

In Construction by Giovanni ValleLeave a Comment

Scratch coats are one of the most important parts of doing your own masonry or putting together a new decorative concrete look to your home. It has a reputation for being a “make or break” point–especially when it comes to the drying process.

How long does it take for a scratch coat to dry? Scratch coat drying times can vary but typically will require around one to two days of dry time. If you decide to “moist cure” your coat, it can take between three to five days of time.

Having a well-done mortar scratch coat that’s given time to cure is important for any decent masonry project. Before you put on that scratch coat, make sure you know your timing.

How Long Does It Take For A Scratch Coat To Dry?

A scratch coat is one of those things you really can’t ignore. Without the scratch mortar present, cement won’t be able to bind as well as it should. This, in turn, weakens your masonry. Scratch coats can be applied with one of two main methods:

  • Moist Curing. This involves using a misting hose to add additional moisture to the scratch coat once it’s been applied to the frame. This helps improve the strength of the scratch and also prevents other coats from sliding off during application.
  • Direct Drying. This is the older method which involves using no moisture during the drying process. It’s considered to be okay for patch jobs and for jobs that need to be done fast. This can cause coats to be difficult to work with.
  • Bonding Agents. If you’re using Flexi-Bo or another bonding agent as a way to get your wet cement to dry cement, this can change your outcome.

How Do You Make Scratch Coats That Dry At A Standard Rate?

A typical scratch coat is composed of three parts sand to one part concrete. This yields typical drying times. If you add lime or other ingredients into the mix, you might notice drying times lengthen a bit.

Scratch Coat Drying Times (No Moist-Curing)

If you’re just using a scratch coat made for a quick fix, then you probably don’t need to moist-cure your coat. This is especially true if it’s for stonework that doesn’t require too much structural integrity or is going to be reinforced with other materials.

Getting your scratch coat to dry without moist-curing is a fairly quick process. Depending on the conditions surrounding your masonry, it can take anywhere from 2 to 48 hours.

How Long Does A Moist-Cured Scratch Coat Take To Dry?

Moist-cured scratch coats can take a while to dry, depending on how thorough the moist-curing process is. Most projects will require moist-curing for several days, though the amount of moisture added to the scratch coat may change drastically based on environmental factors.

  • Typical projects will require several days of moist-curing time, plus a day or two of dry time. With a standard moist-curing process, you can expect your scratch coat to dry in one to three days after moisture stops being applied to the masonry. 
  • Projects in areas of extreme drought may require more intense moist-curing, but less dry time. It’s not unusual to hear of moist-cured scratch coats drying in a matter of hours when the heat is unusually high. 
  • In moderately high levels of humidity, it can take up to three days for your scratch coat to fully dry. Any longer than three or four days is considered to be an exceptionally long time to dry. However, if it’s raining on a near-daily basis, you could get stuck playing the waiting game for your cured coat to dry.

How Much Moisture Will I Need For A Scratch Coat Cure?

This can depend on the scratch coat as well as your environment. Hot, dry environments (like those in deserts) could require constant misting in order to ensure that the coat doesn’t flash dry. Wetter environments might require a brief mist.

How Does Moist-Curing Affect Your Scratch Coat?

Your scratch coat needs to be moist-cured in order to harden and build the resilience required for structural integrity. It helps stone masonry adhere to the mortar, and also decreases the chance of having your base split in two.

Important Things To Know About Drying Your Scratch Coat

Your scratch coat needs to be treated well and dried before you do anything else in your masonry project. Here’s what you need to know about the scratch coat process before you proceed…

Are There Any Additional Scratch Coat Steps I Need To Know About?

This depends on the project, but adding grooves to your scratch coat is generally considered to be a wise choice. Before your coat dries, make sure to add some grooves with a fork or a rake so your brown coat or stonework will adhere better.

Your scratch coat is going to dry in the shape you leave it in. If you need to add extra grooves or add a way to stack stones, this is something you should take into consideration before it dries.

Is Quick Drying Good For Your Scratch Coat?

Drying your scratch coat too quickly can cause it to remain brittle or cause it to be soft. If you intend on bonding additional layers of concrete or stone to your project, it’s best not to do this. In fact, most major building concepts should have a scratch coat as part of their base coats.

What Can Influence Coat Drying Time?

There are a lot of different environmental factors that can change drying times, which is why some masons choose to plan their projects around the local weather. The most common things to watch for include:

  • Sun Exposure. Bright sunlight can speed up drying times immensely.
  • Dry Weather. A rainy, humid environment can slow down drying times and make curing more effective. Dry weather will make concrete fix faster.
  • Wind Speeds. Much like with any other typical “blow dry” effect, a day that has low humidity and higher wind speeds will mean faster drying times.
  • High Temperatures. High temperatures are one of the most reliable indicators of fast drying time.
  • Concrete Moisture Levels. If your concrete had a consistency that is a little more watery, you may have a longer drying time…and you might need an extra layer of scratch.
  • Drainage. If your walls are stuck in an area where they’ll sit in a pile of water for a long time, drying times will obviously get delayed.

How Can You Tell If Your Scratch Coat Is Dry? 

The easiest way to tell if your scratch coat is dry is to examine your coat’s color. When masonry dries, it’ll gain a lighter color. Most scratch coats will turn a nice, light grey when they are done drying. So, if you’re having trouble telling when your coat’s dry, just keep an eye on the color.

How Long Can A Scratch Coat Possibly Take To Dry?

In most cases, a scratch coat will not take longer than three days to dry. However, there are times where your scratch coat can take an inordinate amount of time to dry fully. This usually happens in extremely humid conditions, or during times of heavy rain.

When this happens, you can expect your scratch coat to take up to eight days to dry. Thankfully, that’s an exception rather than the rule.

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