Bricklaying Question

Does adding washing up liquid to mortar weaken it?

I'm assuming that proper plasticiser doesn't weaken the mortar (given that it's so common), but what does washing up liquid do? I've been surprised to see how common the washing up liquid trick is. No one seems to worry about it but me!

15 Answers

Best Answer

Basic washing up liquid acts as a plasticiser, but reduces the final set strength of the mortar.

Many washing up liquids also contain soluble salts, which cause temporary efflorescence and are hygroscopic.

Answered 19th Feb 2011

ace plastering & building services

Member since 5 Jan 2009

Never use washing up liquid in your mortar mix.
The only place for that is on the kitchen sink.
Use mortar plasticisor.

Answered 20th Feb 2011


Member since 29 Oct 2008

I use concentrated mortar plasticiser, you add just 10ml to a mix(standard belle mixer) It comes in 500ml or 1 liter bottles and has a measuring cap on top its far more practical than standard plasticiser once you get use to it and according to the manufacturer it strengthens the mix!
Using fairy liquid can create bubbles and lead to voids in the mortar. Would a wall acctually collapse purely beacause of fairly liquid? Unlikely, but I would not be seen using washing liquid as its not a proffesional image.

Answered 19th Feb 2011

Adam Bosley Brickwork and Paving

Member since 13 Sep 2009

you are better useing a proper plasticiser when using washing up liquid when set it seems to dry really white probably salts coming out whitch is noticable

Answered 11th Mar 2011

dpc builders

Member since 18 Nov 2010

hi,the days of useing washing up liquid have long gone can buy good quality plastisiser from any good building supplier.thanks nick

Answered 20th Feb 2011

kentish builder

Member since 14 Jul 2009

never use washing up liquid it kills the mortar and give the wall a couple of years and you will be able to dig the mortar joints out with your fingers.anyway plasterciser is not expensive but even if it was its cheaper than a new wall!

Answered 20th Feb 2011

d.a.newton building contractors

Member since 12 Mar 2009

No feedback

you should use plasticiser as opposed to
Washing up liquid

Answered 20th Feb 2011

C Glancey

Member since 20 Jan 2010

Why would you use washing up liquid when it is more expensive than plasterciser!

Answered 19th Feb 2011

Quality Plastering and Rendering

Member since 6 Oct 2008

Plasticiser is the new washing up liquid, dont like to say it but used to use it years ago before the proper stuff came out on the market - Trust me washing up liquid has a weakening affect on mortar, do not use it !

Answered 22nd Feb 2011


Member since 26 Aug 2008

No feedback

Always use feb mix never washing up liquid but only above ground level

Answered 25th Mar 2011

The brickwork specialist company

Member since 25 Mar 2011

its a big NO NO. ive heard storys of people having to pull there work down because of this. plus the proper plasticiser only costs about £6 and will last along time..

Answered 19th Feb 2011

northview property mainenance

Member since 13 Sep 2010

you should never use washing up liquid it will kill the cement, in time your mortar will start to crumble.Always use a plasterciser and you will have no worries.

Answered 20th Feb 2011

c grimwade brickwork

Member since 22 Jan 2010

hi dont use washing up liguid thats for pots ha ha allways use plasterciser you will have no worries

Answered 20th Feb 2011

complete joinery service

Member since 3 Mar 2009

its something to do with the amount of bubbles coating the sand and it can not be controlled when using washing up liquid

Answered 29th Apr 2011

L.Russell general builders

Member since 23 Dec 2010

I have seen builders use this and seen the end results which were not good.It looks quite funny when you see a builder mixing and he is stood there with the fairy bottle !!! You are always better using a good quality plastisier.

Answered 20th Feb 2011

Tomlinson Roofing

Member since 14 Sep 2010

Need help with your project?

We have tradesmen ready to help you. Post a job, read reviews and hire today.

Post a job

Need some help?

Post a job on MyBuilder to find quality, local Bricklayers who can help you with your project.

Search all questions