How long before rain on mortar?

[James Davis]

Hi all,

Block wall was built up to 5 course yesterday, fibolite. Last ones went in just before 8pm. It has rained over night although it was dry or at least very light rain in the first few hours after last blocks went in. Looks like heavy rain due all afternoon today though.

How long before the mortar is dry enough to withstand being rained on?

 

[Mottie]

Can you chuck a tarpaulin/plastic sheeting etc over it if you’re concerned?

 

[^woody^]

Mortar sets in a few hours.

You would only be concerned if you wake up and all the water is washed out and on the floor.

 

[stuart45]

Mortar sets in a few hours.

You would only be concerned if you wake up and all the (water) mortar is washed out and on the floor.

Predictive text gets you every time.

 

[noseall]

Block wall was built up to 5 course yesterday, fibolite. Last ones went in just before 8pm. It has rained over night although it was dry or at least very light rain in the first few hours after last blocks went in. Looks like heavy rain due all afternoon today though.

How long before the mortar is dry enough to withstand being rained on?

Mortar loves water. Whilst it's not good to lay blocks soaking wet, the blocks being rained on will only make the mortar stronger. Once the gear is trapped in between brick/blocks, it takes some pretty serious squally-rain to do any real damage.

 

[James Davis]

Why does the blocks being wet matter?

When you say soaked, do you mean like taken from a puddle soaked, or wet patches on the blocks because they've been stored out in the rain all day soaked?

 

[noseall]

Why does the blocks being wet matter?

When you say soaked, do you mean like taken from a puddle soaked, or wet patches on the blocks because they've been stored out in the rain all day soaked?

Left overnight in the River Trent soaked. As the wall dries, it tries to shrink back, sometimes cracking the blocks. They are a bu99er for it.

Conversely, mortar (as with all cement based mixes) loves to be kept damp throughout the curing process. Deny it water, i.e. force it to dry too quickly and it will turn to dust.

A bit of rain won't hurt.

 

[James Davis]

Interesting, thanks.

Funny you should say that as the old extension on my house, which was built in the early 70s and is on the sunny side of the house, has really terrible pointing. The grains fall out like dust if you rub your finger on them. My builder speculated that they must've built it during a hot summer and that the mortar got dried out too quickly. I had assumed there was a cement shortage.

 

[Munroast]

indeed, the longer it takes to dry out the harder and stronger it becomes, some weird chemical reaction takes place where the H²O (water) molecule is used in the creation of the cement - this process takes time so the longer it takes to dry out the better

a little experiment to try - weigh all the ingredients of some mortar, let it dry thoroughly over 6 months or a year (sadly I have done this) and although it will be a little lighter as some of the water has evaporated off - maybe a third of the water you had used in the original mix is still in there - but it is now not water!

 

[James Davis]

LOL!

What's weird is I've seen pretty much all the episodes of Tales of the Unexpected even though it was before my time.