painting a parge coat

[mjc55]

We are building a Pod where we will live on site whilst building the house.

 

We don’t want to finish the internal walls (plasterboard probably) of the Pod yet as this is a task for when we can move into the house and rearrange the Pod (to include a store room with external access)

 

This is an Ecobrick build - we are mimicking the main house so that we can potentially sort out any issues before the main build,

 

I was wondering what would be best for "painting" the parged walls to a) lighten them  and b) reduce the roughness.

 

Any suggestions welcome as what makes sense to use as a short term (no more than a year hopefully) solution.

[JohnMo]

Our walls are Durisol (pre Ecobrix), we parge coated with a cement, lime, building sand. Mixed with water to a double cream consistency. Then applied with a broom. It fills all the holes in the block and all joints. Wall becomes airtight after. Should last for ever. If want any colour other than grey paint it after.

 

[JohnMo]

Mix ratio is on here

https://forum.buildhub.org.uk/topic/25228-airtightness-parge-coat-vs-airtight-paint/

[mjc55]

Thanks for that but we have already applied the parge coat.

 

The question is about what to paint with as a temporary - but I would expect to be in the pod at least 9 months so want something other than the grey parge coat finish.

 

 

[JohnMo]

Masonry paint or emulsion.

 

Try on a small area, make sure it stays put before you commit.

[Redbeard]

Lime wash. Make your own if you wish with 'bag-lime' (hydrated lime from mainstream merchants)

[Oz07]

Why is everyone using lime in the parge mix @JohnMo are you just using it for workability? I used plasticiser in mine.  

[JohnMo]

59 minutes ago, Oz07 said:

Why is everyone using lime in the parge mix @JohnMo are you just using it for workability? I used plasticiser in mine.  

I asked Google why did I do it, as it now 5 years since I did it.

 

Lime is added to cement in mortars and renders to improve workability, flexibility, and water retention. These properties make the material easier to handle, create a better bond with the substrate, and increase durability, especially for older or softer building materials. Lime is sometimes combined with cement to balance the strength and setting times, allowing it to be used for projects with different requirements. 

Benefits of adding lime to cement Improved workability: Lime makes the mortar smoother and easier to spread, which helps achieve full, well-bonded joints.

Increased flexibility: Lime adds flexibility to the mix, which helps prevent cracking caused by brick and mortar expansion and contraction.

Better water retention: Lime holds water within the mortar, making it more cohesive and improving its application to porous surfaces.

Enhanced breathability: Lime-based mortars are more vapor-permeable than cement-only mixes, which allows moisture to escape and prevents dampness and frost damage.

Improved bonding: Lime provides a better bond with the substrate, creating a more durable and protective finish.

 

[Mike]

1 hour ago, Oz07 said:

Why is everyone using lime in the parge mix

In addition to the above, lime is also strongly alkaline, which inhibits growth of mold & fungi.