Sanding a deck

juraj.kecso

Hi All, 

Last summer I stained a decking area in my house (around 8x4 metres). Within a single season parts of it got scuffed and flaked. 

It is an older decking and wasn't being looked after much by the previous owner.

This year I decided to go with oil.

I tried pressure washing the remaining stain off. It came off in some parts. There are parts where it holds very stubbornly.

I decided sand the whole thing down and start fresh with nice smooth surface.

I will be hiring one of those big floor sanders to make the job a little easier. Anyone used one of these on a decking?
I was thinking that I'd start with 40 grit and use 80 as the final grit? Would that be fine or should I use 120 grit too? I don't want the surface to look too rough, but I also don't want to end up with an ice rink.

Also how many sheets of each grit should I get for a job this size? Can this be done in a day?

Any advice would be much appreciated.

Gunner276

40 grit might be a bit much. I'd start with no less than 80 grit!

juraj.kecso

No more or no less? Would you then do 120 grit or will 80 grit be enough? There is a lot of existing stain on the surface. How long would you think this could take?

DB1904

What do you intend to do with the grooves?

juraj.kecso

No grooves, the decking is with the smooth side up

Gunner276

40 will remove a lot of material. Depending how smooth you want it after you could go to 180 or 240 grit

juraj.kecso

Thanks. How long do you think it would take to do a 8x4m decking? 

Grenage

Not very long; you could do that amount with an orbital sander in a day so a floor sander would be much quicker.

juraj.kecso

Thanks. How many sheets of each grit 40, 80, 120 should I get?

juraj.kecso

One more thing, I would also like to treat the decking with anti-mould and anti-algae treatment, something like Ronseal Decking Cleaner. Should I do that before sanding (with a lot of stain still present) or after sanding (and potentially risking raising the grain again)?