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General tips about sanding and drywall compound...

When repairing drywall, your goal is to do as little sanding as possible.  It's almost impossible to make a repair without at least a tiny amount of sanding.  The best pros hardly sand at all, but this ability comes with years of experience and lots of sanding along the way!  That's one reason why the pros work so quickly... they are precise and know their products intimately 

 Sanding drywall compound produces a fine dust that gets onto and into everything.  Because it is water-soluble, wiping the dust with a sponge makes a royal mess!  By collecting the dust at the work area, either through wet sanding or through use of a vacuum, you eliminate much of your cleanup.  Since small holes generate small amounts of dust, these simple methods are more than adequate.

The best way to minimize sanding is:

Between coats, use your drywall knife to shave off any lumps instead of sanding them.  If you've followed these tips you should need minimal sanding.

Back to hole repair.  First things first... look at the hole!

Know thy drywall!  Drywall is made from a special durable paper that is pressed onto a pressure-formed layer of compressed rock dust, a.k.a. gypsum.  The gypsum gives the wall its hardness and the paper protects the gypsum from moisture while providing a smooth surface for painting while adding some flexible strength.

The smaller and "neater" the hole, the easier it is to fix.  Here is a rough guide:

  1. Holes up to about 1/2" can be filled with most wall patching compounds, such as drywall compound or light duty spackle.
  2. Holes between 1/2" and 6" can be repaired with a piece of drywall and drywall compound. 
  3. Holes larger than 6" can be repaired with a piece of drywall and drywall compound but should have reinforcing wood strips installed in the wall to support the drywall edges.
  4. Since wall studs are a maximum of 14 1/2" apart, very large repairs will bridge across one or more studs.  We'll talk about large repairs in another article.

Repair rules for very small holes...

Very small holes in drywall... from nails, screws, picture hangers, wall anchors...  don't need much preparation aside from cleaning away any dust.

Repairs for medium sized holes - up to about 6" across

There are two ways to repair these holes. (There are more but I want to get home for dinner.) I prefer the first but some people like the second.  The second is definitely easier, though!

Method 1: Plasterboard patch screwed to supporting braces

Method 2:  Plasterboard trimmed and glued directly to existing wall

I said earlier that I prefer Method 1, but frankly Method 2 is so much easier.  I guess it's hard to teach old handymen new tricky techniques!!

Back to dusty, messy sanding...

You're at the point where you have a fairly level patch (you have gotten good, haven't you!) but there are some rough spots.  Now is the time to consider sanding.

First of all, it's always better to fill than sand, so if you have any small holes or "bubbles", try filling them with thinned compound first before resorting to sanding.

There are no two ways about it.  Dry sanding is dusty!  There are attachments for vacuum cleaners that use sanding screens... plastic sheets with thousands of holes that are impregnated with carbide abrasive.  The vacuum sucks the dust through the holes as you sand.  They are not 100% effective, but get virtually all of the light dust which is the most messy.  Any larger particles that miss the vacuum will just drop to the floor for cleanup.

If you don't want to purchase one of these special sanding kits, you can simply hold the vacuum cleaner nozzle under the repair as you sand, which will catch much of the dust.

Wet sanding has its fans...

I'm not too big on wet sanding since it can smear the compound.  But it is the closest thing to dust-free drywall sanding there is.  If you decide to wet-sand, don't use too much water and be careful not to oversand or you'll rub off too much compound and have to recoat the repair again! (Don't feel bad... even pros have to go back and touchup their work!  At least the conscientious ones.)  There are special sandpapers that are designed to be used wet, and there are also sanding screens that work well with water.   Again, don't get the patch too wet!

When the repair is done...

No matter how large or small the repair, you should prime and paint the patch.  This protects the patch from moisture and will make it even more invisible.  I prefer to use Kilz oil primer/sealer for patches where I am only going to touchup the finish paint.  Kilz doesn't seem to cause "flashing" because it does not dry smooth.  Because it is an oil primer, it won't dissolve or soften the drywall compound.

Shellac-based primers make patches very shiny and this shininess seems to show through most finish paints, even multiple coats.  I've had mixed results with latex primers, but the one's I've used seem to be resistant to flashing.