How do I sand underneath a deck?

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Forum topic by edogg posted 07-16-2010 06:52 AM 2172 views 0 times favorited 17 replies Add to Favorites Watch
View edogg's profile


2 posts in 2294 days

07-16-2010 06:52 AM

I am thinking about refinishing my 20 foot deck that comes off of my master bedroom. The paint and boards are chipping and even cracking and its really ugly. I plan to sand it but what is the best way to sand underneath the deck?

Part of me just wants to buy new pieces of wood and replace it but the length of boards I need is turning out to be pretty pricy. I’m a real amateur here that is looking for ways to save a buck and improve my home ;)

Any suggestions??

17 replies so far

View KayBee's profile


1083 posts in 2668 days

#1 posted 07-16-2010 07:21 AM

A 20 foot ladder to reach the underside of the deck ; )

then some bengay and a neck rub for the sore neck..

-- Karen - a little bit of stupid goes a long way

View ChrisCarr's profile


196 posts in 2320 days

#2 posted 07-16-2010 07:27 AM

I Am not sure if I understand but, underneath your deck it is high in the air? If so try a ladder and use a portable belt sander.(be careful with the cord, or use a cordless one.) And to stain or paint just get on the ladder and use a small sprayer.

For the actual deck where you walk, you could rent a floor sander and it will make quick work if equipped with a coarse grit paper. However you could use the belt sander there too but it is quicker with a floor sander.

To make sure your new paint/ or stain lasts long use a top quality brand (if you can afford) and apply multiple coats. Be sure you allow a coat to fully try before starting the next.

An alternative to sanding could be scraping or portable power planing but I would not recommend it unless the paint is VERY thick.

View Broglea's profile


677 posts in 2512 days

#3 posted 07-16-2010 07:28 AM

I’d use a power washer to get most of it off, let dry, then paint. Pictures would help us see what your faced with.

View edogg's profile


2 posts in 2294 days

#4 posted 07-16-2010 08:02 AM

Thank you all for the replies. I will try to take some pics tomorrow to give you a better idea. I have bengay downstairs ready to go ;)

View Rick  Dennington's profile

Rick Dennington

5107 posts in 2616 days

#5 posted 07-16-2010 08:28 PM

Greetings edogg,

You can stand under your deck if you’re not too tall….....or….

-- At my age, an "all--nighter" is not having to get up and pee...!!!

View SKFrog16's profile


661 posts in 2622 days

#6 posted 07-16-2010 08:42 PM

Rick, thats how we got our back problems!

-- Methods are many,Principles are few.Methods change often,Principles never do.

View FirehouseWoodworking's profile


684 posts in 2695 days

#7 posted 07-16-2010 09:31 PM

Not knowing the actual configuration of your deck, a couple of thoughts here . . .

If your deck boards are screwed down, number them with masking tape labels, unscrew them, sand the undersides, then screw them back down. If the deck boards are nailed down, FORGET IT!!!!

Another option is that you may want to think about renting a sandblaster.

Still another option is to rent some scaffolding. Set up a platform so that the top is about 3 or 4 feet below the deck. Get a mechanic’s creeper, some good goggles, and a particulate filter face mask. Lay down on the creeper and sand to your heart’s content. Don’t laugh. I had to do this on a job one time. Didn’t turn out to be to bad. Course I’d have gone with the sandblaster but I hadn’t thought about it. A friend suggested it AFTER I’d finished the deck!

At least you’re asking for suggestions before you start!

Good luck!

-- Dave; Lansing, Kansas

View a1Jim's profile


115177 posts in 2999 days

#8 posted 07-16-2010 09:35 PM

I build lots of decks and if the wood is looking that bad I think your better off replacing it for appearance and safety reasons.

-- Custom furniture

View Swede's profile


191 posts in 2440 days

#9 posted 07-16-2010 10:12 PM

Blasting upside down is not something I wish to consider doing.

I am with “a1Jim” better off to remove the lumber and replace it.

This is only my opinion and not to criticize anyone else’s suggestions.

-- Swede -- time to make some sawdust

View TopamaxSurvivor's profile


17577 posts in 3098 days

#10 posted 07-17-2010 02:19 AM

Why would you want to?

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Al Navas's profile

Al Navas

305 posts in 3297 days

#11 posted 07-17-2010 03:17 AM

It is hard to make a decision on only visuals. We are going through something similar now. But good inspections are a must, as what you see could mean structural issues, too (unless your deck is much newer than ours):

In the middle of a “simple” repair job to the deck, we discovered structural damage. As a result, got a new estimate; a complete replacement was required. Here, the initial work, and the contractor working on the revised estimate for the new scope of work:

The old deck partially removed, and work underway:

We expanded a portion of the deck – the renovated 500-sq-ft patio will be below it:

Whatever you choose to do, make sure you will have a solid deck. I learned just recently, with our near-40-year-old deck…. I have posted several articles on this work on my blog.

-- Al Navas, Country Club, MO,

View grizzman's profile


7782 posts in 2725 days

#12 posted 07-17-2010 03:17 AM

have you thought of covering it with a quality plywood and either paint it before you put it up or use a sprayer…doing that much work on a high reach is going to kill your arms and neck…very hard work when your working over your head…either that or pull the boards and plane them..then put on a good finish…but i would not attempt to sand …but your choice…grizzman

-- GRIZZMAN ...[''''']

View richgreer's profile


4541 posts in 2496 days

#13 posted 07-17-2010 03:24 PM

I would power wash the entire deck, top and bottom. Let it dry and sand the top wherever it needs it and then apply a finish.

No civilized man (or woman) should do extensive sanding over their head.

You can usually rent a power washer. You want at least 2500 psi. It’s amazing what they can do.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View John Ormsby's profile

John Ormsby

1283 posts in 3159 days

#14 posted 07-17-2010 04:28 PM

First of all it is very bad to paint a deck. The boards will get dry rot. It is best to use a deck oil and never paint. Even the so called solid sealers will cause problems.

I suggest you do a thorough inspection on the planks and determine if they should be replaced. I have seen this many times over the years.

-- Oldworld, Fair Oaks, Ca

View canadianchips's profile


2310 posts in 2419 days

#15 posted 07-17-2010 05:24 PM

My suggestion :
This may sound strange, but if you spend the money and “DO IT RIGHT the first time,” you won’t run into any surprises later in the project and have to repair that area as well. I always recommend overkill in the floor joists. If 2×8 24” code for your area go 2×10 – 16” O.C. Keep in mind Code is usually minimum.
Spending the money, do it right, looks good, you will improve your home. GOOD LUCK.

-- "My mission in life - make everyone smile !"

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