Stripping and sealing a redwood deck

Robert Fisher

New member
Well this section doesn't seem to be very active but hopefully I can get a response here instead of posting it to the general forum...

The people involved aren't quite sure of the accuracy of these details, but this is the story they gave me:

A neighbor/friend put an water-based Behr (possibly) sealer on his deck about a year ago. They felt it needed to be done again so they asked 'their contractor' (a licensed handyman/remodeler type and the guy that built the deck in the first place) to re-seal it. He apparently used an oil-based Thompson product directly on the deck without any prep.

Now they have a dirty oily film on the deck that is coming up on their shoes, their kids' clothes, etc. They know, of course, that I have a pressure washing business so they asked me what I could do about it. This is one of those situations where we have done each other's families many favors over the years, and while nobody's keeping score I figure we owe them one for some recent considerations.

I mostly do hoods, gas stations and sidewalks; I researched decks some years ago but came to the conclusion that there weren't enough of them around here for me to move to daytime work, so while I haven't done much wood I'm somewhat familiar with the basic process. This situation, however, sounds like one of those tricksies that can turn into a nightmare so I thought I'd sound out the experts before I went any farther with this.

My inclination is to strip the deck, give them the information on how to properly seal it and let them do that, but I may wind up doing the whole thing. The deck is redwood and fairly new, so I'm particularly concerned with the integrity of the wood, and not making fuzzies and that sort of thing. I definitely don't want to create a liability for myself and/or screw up their deck over a favor.

Any tips, tricks or advice will be greatly appreciated (I've already thought of 'run far, far away' but that's not really an option). A general blow-by-blow or a link to one would be helpful as a refresher, but I'm particularly interested in the issues this combination of oil/water sealers (and wood) presents, if anybody has some experience with that.

Thanks in advance,

Carolina Prowash

Exterior Surface Pros
OMG - what a nightmare combination. I would strongly advise that you turn this one down if it's a "firstish" experience on a deck. Redwood with a Behr/Thompsons' combo is probably the WORST scenario you could ever come across - OMG again (sorry).

First - it's very difficult to get off either stain separately without an extremely hot mix applied more than once. You will be following with a considerable amount of sanding.

You may be much better served to pull off the deck boards, run them through a planer and put them back. You could also look at flipping them.

Second - you could be looking at losing your friend over this. It is not going to be an inexpensive process. Very delicate balance when there is any type of relationship beyond paying customer/contractor. One of you will end up pissed before it's over. Now, if you go into this with both of you understanding that he is paying for all materials and some labor for you - considering your lack of experience - you could work on it as a learning thing. It will likely make you never want to do a deck again :)

If you choose to move forward, HD-80, boosted followed by Citralic (and be very careful with your neutralizer on redwood as it doesn't behave in the normal way) is going to be a starting point. (

Our phones are always on.......


Beth & Rod

SR Wood Geek / Moderator
I want to add one point of clarification....
Flipping boards doesn't always work, and very often you end up with splintered areas around where the nails were. Many see it as (sorry) a cheap way out. Counter sinking nails and sanding after stripping is the best option, and if you have to replace the board, you end up with a better look than flipping them most of the time.

For more wood care information try visiting

Great forum for wood care!

Big Mike

HD-80 boosted with Sodium Hydroxide

UMM.... HD-80 is sodium hydroxide & sodium metasilicate. The "boost" is propylene glycol.

As to what other have said, yes this is no job for a first timer. Behr is tough, but Thompsons, not so much. Redwood is a touchy wood to deal with, and not as forgiving as PTP or WRC. Sanding might be your best option.


New member
I have always added more Hydroxide to boost, ( and yes I knew that HD-80 also had Sodium hydroxide in it) never tried Propylene glycol before?

Robert Fisher

New member
Thanks for all the replies... it's clear that this is exactly the kind of nightmare I suspected it might be.
Seems to me that their buddy the contractor owes them some clean-up work, but that's for them to resolve.
Does anybody else think that removing and planing the boards might be the best/simplest solution? Seems to me that if they were going to pull them up to flip them they might as well do that; any further thoughts would be appreciated.
One other question: Is there something I can do to 'wash off' the Thompson's in the meantime (without going so far as to strip the wood)? Their big issue right now is that the stuff is getting all over everything, and if I could at least put a stop to that it would be a help to them, and then they could consider their other options later in the spring.

Thanks again,

Carolina Prowash

Exterior Surface Pros
I want to add one point of clarification....
Flipping boards doesn't always work, and very often you end up with splintered areas around where the nails were. Many see it as (sorry) a cheap way out.

The reason I made that point as an option is that he indicated the deck was only about a year old. I wouldn't call that the "cheap" way out considering the relative newness of the deck. :shrug:

One other question: Is there something I can do to 'wash off' the Thompson's in the meantime (without going so far as to strip the wood)?

I don't think you can just "wash off" Thompsons - but then again, it shouldn't be getting all over their stuff either.

Wash it

Go in with a sodium Hydroxide based stripper and wash it. You'll at least get the oil up. You may find that the Behr comes up some too. It can be a tough job, but if you go in with a mind set of how hard it's ging to be, then it will be. Relax a bit and go wash off the oil. That shouldn't be all theat bad.