FAQ's - Roof and Exterior Chemical Softwashing

What product would you use to chemically clean my roof and building ?

skyHIGH Roof and Gutter only uses Wet and Forget® Moss, Mould, Lichen and Algae remover in our softwash process. This process removes moss, mould, lichen and algae.


It is not a high pressure wash and does not remove cobwebs, dirt and grime and other airborne contaminants.   



Can you clean my roof and house during Auckland's water restrictions ?

Yes we can !!! We use a 1000 Litre tank trailer full of rainwater collected from roofs outside Auckland's metropolitan water supply so we are fine to carry on softwashing in any period of water restriction.

Why use Wet and Forget® over other softwash spray solutions out there in the marketplace ?

Wet & Forget® Moss, Mould, Lichen, Black Fungi & Algae Remover has a unique combination of biodegradable selective surfactants for moss, mould and lichen removal on absolutely ANY exterior surface. 
Wet & Forget® Moss, Mould, Lichen, Black Fungi & Algae Remover is the safest, most effective way of removing these growths.

When diluted with water and applied, it immediately attacks those unsightly growths such as moss and mould. Each time it rains, this safe, cleansing combination reactivates to help flush away the moss and mould without scouring the surface it has infested.

Some products using other chemicals, notably sodium hypochlorite, may show quicker results initially, but they have no lasting long term activation properties. Wet and Forget® is designed to provide long term cleaning action and reactivates again each time it rains.

Is Wet and Forget® safe to use when i have pets or stock?

We recommend that you keep your pets and stock either well away from the wash area or inside your house as applicable until after the area has been well washed down with fresh water.

In the event that they accidentally get into an area that has been chemically washed, it is best to give their paws and backsides a wash with fresh water to be on the safe side.

We also recommend that all pet food bowls are tipped upside down or removed from the wash area.

It is also important to cover any outdoor fish ponds to avoid any spray or wash going into the pond.

I am on tank water. Can i still get my roofs chemically softwashed ?

Sure can. But you must disconnect the water supply to your tank for at least 4 weeks with a few showers OR have at least 36 mm of rain with colour steel or similar roofs and about 50 mm with tiles and shingles to remove the concentrate and detergents.


We recommend that you consider getting your local plumber in to install some diverters so you can easily stop any treated water from entering your tank. You may wish to check that all water is getting correctly diverted by squirting a water hose down each down pipe and checking that that water is not going into your water tank.

( note that the flip open style of downpipe diverter may not adequate to stop 100% of the chemical wash going through the downpipes. Double check that they are completely open as they may not stop the chemical wash if they are even slightly out of position ) 

Please note that the Customer is to open all water diversion systems prior to the roof wash if you are water tank. Skyhigh will not accept any responsibility for any diverters that are not correctly opened prior to the wash.


From time to time we are asked to cut a downpipe ( or we may recommend a downpipe should be cut before doing the wash ) or we may be asked to disconnect downpipes or open diverters in order to divert the chemical wash from your water tanks. Skyhigh accepts no responsibility for any incorrect cut placement or damage due to disconnecting downpipes or incorrect diversion of chemical wash from your roof.

Check that the water coming off your roof is not foaming before you reconnect your water tank intake pipes.

Wet and Forget® has been used for over 35 years to treat biological growth on roofs.

Please note that Skyhigh accepts no responsibility for reconnecting your water tank too early before the chemical detergents has been washed off your roof with rain. 

How long does it take to Wet and Forget® to work ?

It is mainly dependent on the intensity of the contamination. If it is really light you will see results within days. Otherwise it may take longer. Your concrete may turn an orange brown when the Wet & Forget® is applied. This is normal and shows there has been a good reaction. The discoloration will dissipate over a short period of time and is not permanent. The good news is that when applied again the following season, the clean up will occur within weeks. In the very worst case scenario where contamination is extreme, it may take 6-12 months.

We are regularly advised that clients wish to have their roof cleaned in order to carry out a repaint. A chemical wash is ideal for this as unlike a water blast, it will kill the spores and stop growth reappearing under the new paint.

However - you must be patient and let the product work BEFORE you get the paint out. 

In our experience, each site is different - some very bad black mould roofs / fences , soft stone surfaces may need a 2nd treatment a few months after initial chemical softwash to totally kill the mould. Other places with years of black mould build up may need a waterblast after the mould has been killed in order clean it up to prep for painting if you can't wait for the dead matter to weather off due to your repaint schedule. ( Skyhigh does not do waterblasting )

( Note that it is far easier to waterblast the dead matter off a roof than trying to blast living mould and

lichen off. In some instances, it is impossible to totally remove black mould. ) 

Other factors that influence how quickly the dead growths disappear are 

Type of roof surface eg tiles tend to take longer than colour steel

Steepness of roof for rain water flow velocity off the roof

Angle of house roof to prevailing weather

Type of growth - black mould or lichen ?

Time of year - amount of rain and heat.

Surrounding obstructions to the weather like other buildings and trees etc.

We can't control these factors but the first step is to kill the growths with our chemical wash then let time do the rest. 

When is the best time to apply Wet and Forget®?

On a cool, dry windless day and when no rain is expected for 4-6 hours. We recommend that you wash down outside tiles , timber steps etc after about 5 hours or so as sometimes these can get slippery after application. A simple hose down is all it takes if rain doesn't do the job for you.


Same with windows - you can either hose them the next day to clean off the residue, or just let the rain wash them of product. 

You may also notice some spray residue on exterior joinery and weather boards. This is just the dried surfactants within the wash. This will come off with abit of weathering, rain and time.

Will Wet and Forget® damage my plants ?

It may be advisable to cover delicate plants close by with plastic or paper just to ensure they don't receive any overspray. Again a hose down after the wash is always a good idea. 

Please be aware that some flowers do not like any chemical wash spray whatsoever and will die off even after a watering down.



Please contact us if you have any further questions. Thankyou.