[Denise l]

Hi, Any suggestions on removing black mould and green algae from external concrete render. What chemicals and what pressure washing? for 3 storey commercial building.

Thanks

D

[martin19842]

hello Denise

is this a smooth render or roughcast,??

what condition is the render in ?? ie sound and bonded to the wall well, or has it blown, and peeling??

all of these factors would contribute to how you tackle the job, as too much pressure/water and the render could end up on the floor.

also why are they looking to have it cleaned, redec purposes? or to make it look better without repainting, if the latter what state is any paint covering in , as this can lift off very easily.

depending on where it is, we might be interested to take a look at the site, and provide advice, or a costing, as we have done this type of work before, using hot washers, and cherry pickers in difficult access areas.

regards
martin
martin@dcscontract.co.uk
07850605162

[Denise l]

Hi, Thanks for your answer. The render is rough cast and is a few years old. The builders ran out of money so it was left to another company to finish. The paint is ok, not peeling or anything. They are trying to see if they can get away with not painting if the cleaning will be cheaper. I just dont want to be the one left with a damage claim. Did a test area with cold pressure washing and it did look better but not perfect. Have been told to use a hot pressure wash of 98 degrees but low pressure.

[martin19842]

hi there

when you do your quote just ensure that you include in it disclaimers with regards to the paint and peeling etc etc.

good luck

regards

martin

[Denise l]

Thanks, thats a really good tip

Denise

[Richy L]

Hi Denise,

I'm based in Cardiff. As the job may be too far for Martin, I would be happy to do it for you. I am based in Cardiff.
I have also done lots of this and I do a lot of work for a large decorating company in Cardiff.
I have a hot washer  - up to 150 degrees.

If you want me to look at it give me an email on richard@leeksons.com or call me on 07940 125 275.

Thanks

Richy

[Neil kell]

The green algae is not the problem, that only rain, that'll whip off the second you hit that with the washer. Find out how long your black mark has been on there. It may never come out if its been there long and depending on what it is. What I mean is you can get it out but you can kiss the render goodbye too you know what I mean. Be careful you are not being led to the slaughter here, do you know the builder well? What about just camoflaging the stain after you remove the algae. Or the render could be fine to use a high psi 3000 washer on it, i really doubt it though, don't go too close. Try a test area out of site first. But render is dodgey it will be all in your hair and everything, the amount of times ive been blinded by that stuff . If its a bitumen based stain (oil or tar type from the roof, it dripps down when they are fitting the felt on the roof) its not going anywhere its at home where it is. Camoflage i.e paint over it or get the builder to re render it instead of setting you up for the fall. They have no conscience I swear, ha.

Neil

[Neil kell]

You meant monachuche right?