How to Build a Sandbox with Seats

All wood sandbox plans

After a year with the plastic turtle sandbox, it was time for an upgrade. My son is now 3 and the time has come to make a real sandbox. There are of course many sandbox plans online, and mine follows one of those plans (Bob Vila's simple sandbox and deluxe sandbox), but here I'm going to give you my real-life step-by-step build, with ALL the gritty details often left out of those shorter how-to articles. So yes, it is long and has many steps for a sandbox, but I prefer to leave nothing out, for those that are actually about to build a sandbox.

If you don't want to make something so elaborate, you can simply nail some old boards together and fill it with sand. Done! I tend to make things much more involved... Still this is a very easy sandbox to make.


Here's the finished sandbox. This gives you a good idea of what a 6 by 8 foot sandbox (inner box dimensions only, does not include seat overhang) looks like with a 3 year old in it for size. There's a 1 year old brother getting sandbox ready soon, so knowing they don't like to share, I figured we'd need a big sandbox. Note: You can click on all photos to enlarge them.

Total sand weight is 3,000 pounds! Sand will be your biggest expense in the project, so keep that in mind when determining your sandbox size. This is a 6 x 8 foot sandbox with 2 x 12 Hem/Fir boards, not pressure treated. The sand in the box is 8" deep.

Step 1. Drink some wine and make a mock up with paint stirrers!

I enjoy upfront planning, so hey why design your box with feather light boards rather than figuring out your design with heavy boards. Maybe you only want seats on one side, or two sides? Maybe you want multiple levels, or an extra box on one end for toys?

At one point I was thinking about making truck garages on the insides, and double walls that would house things like a solar panel powered radio, and pvc pluming for a water feature! I also was trying to figure out a cover that converts to a shade! This mock-up helped me reel-in my imagination and stick with the basics... Add-ons can come later. lol.

Step 2: Find a good location, and decide on the size

For location, you'll want: to be able to see the kids from inside you house, some shade and not directly under a tree (too much falling debris and cutting down into the roots, for the box excavation, can be hard on you, and the tree). For size you'll want upwards of 4 x 4 feet. I used some old pvc pipe to play with design variations and to help me imagine the size in the back yard. I also stuck a stick in the middle to observe how much sun that area received throughout the day.

Keep in mind this plan has seats that eat into the box area a bit. If you make it too small, it could look like this, nice work, but perhaps too small for the big toys kids seem to have these days.

Here's the Plan for this Wood Sandbox


Step 3: Wood and hardware for the sandbox

My sandbox plan uses all 2x12s and one 4x4 for the corners. Basically I'm building a box (2 8ft pieces and 2 6ft pieces), and seats on top of that (2 8ft pieces to be cut down for the 6ft sides, and 2 10ft pieces to be cut down for the 8ft sides). The seats are longer than the box sides, because I'll be cutting 45s where the seats meet each other.

Here's the lumber you'll need:
BOX:
2x12s 8ft (2 needed @ $13.83 each) Have the home store cut 2 16ft pieces in half.
2x12s 6ft (2 needed @ $10.37 each) Have the home store cut 1 12ft pieces in half.
4x4 8ft (1 needed @ $8.91) You'll cut this into 4 11.25" pieces.

SEATS:
2x12s 8ft (2 needed @ $13.83 each) Have the home store cut 1 16ft piece in half
2x12s 10ft (2 needed @ ~$15.00 each) Have the home store cut 2 12ft pieces down 2 feet

(When I went they didn't have 6, 8 or 10 foot pieces in 2x12s, thus the in store cutting, and I also couldn't transport long pieces)

Total for Lumber: ~$115.00 (no sales tax in our state)

Be picky about your wood. If you tell them it's for a sandbox, they give you the first piece out of the bin. But we want a square box, so no twists, cupping, warping, etc. They'll grumble a bit, but stick to your guns, take pride in your work, even if it's "just a sandbox".

Also be ready for them to steer you towards the pressure treated wood. Tell 'em you want pine or similar (Hemlock/Fir is what I got). Most outdoor, and ground based wood structures call for pressure treated wood, but for a sandbox, your kids will be in it, and you'll be working with it, and by the time your kids have out grown it, it will still be in fine shape. No pressure treated, chemical laden wood needed. By the way, some people turn these into raised flower beds after the kids lose interest.


You'll also want to make sure you can get the lumber home. My lumber did fit in one loaded Rav4. I did though have the wood cut at home store before transport. They'll do this for free, and it will save you some cuts at home.

Here's the hardware you'll need:

6" metal straps for under seat corners (4 needed @ $1.68 each)
5" long, 3/8" diameter, galvanized hex bolts (16 needed @ $1.53 each)
3/8" galvanized hex nuts (16 needed, 1 pack of 25 @ $4.78)
3/8" galvanized washers (32 needed, 2 packs of 25 @ $4.79 each)
3" exterior deck screws (a bunch needed, 1 box @ $8.69)
1 1/4" exterior deck screws (a bunch needed, 1 box @ $8.69)
Total for hardware: ~$63.00 (no sales tax in our state)

Total for wood and hardware: $178.00 (I'll have to double check this as I swear my bill was about $150.00
So perhaps that sounds like a lot for a sandbox, but keep in mind that if you look online you'll spend a lot more for a lot less in quality and size:

Here are some examples of sandboxes online:
$30-$70: Plastic turtle (this thing is tinny and can only fit one truck and some legs)
$679.99: 8x4 foot sandbox (smaller than my 8x6 box)
$99.99: 4x4 foot sandbox (with cover $164.98)

Step 4: Building the sandbox base

Go ahead and mock it up. Here's basically what we are building, but the seats will be cut to meet at 45s and the 4x4 in the front there will be bolted in each corner.


Cut the 4x4 into 4 pieces, each 11.25" long. Remember 2x12s are not really 12" wide, they are only 11.25" wide. Yeah, that's that nominal wood size vs. actual wood size thing... "Nominal" is what they are commonly called, like a 2x4, but the "actual size" of a 2x4 is 1.5"x3.5" for example. These 4x4 pieces will be bolted into the corners.


Here's the basic idea looking down on a corner. You can see that the 5" long bolt isn't long enough to go through the boards. That's why we are going to countersink them. And yes, 2" plus 4" inches equals 6", so why is the 5" bolt just as wide... It's that nominal vs. actual dimension thing again... See how the "4x4 is only 3.5" wide, and the 2" board is really only 1.5" wide...


Okay, so we take our 11.25" section and mark it down the middle of 2 sides and then measure 3" in from the ends on one side, and 2 inches in from the ends on the other side. The holes for the bolts will be offset so the bolts don't hit each other.


Start by drilling the countersink hole with a 1 1/8" spade bit, then drill all the way through with a 1/2 bit into a junk piece of board below. This old bit (above) was dull so I ended up running out to get a new 1/2" straight "speed bit", so much faster, and didn't kill the battery on my cordless drill.


Here's what you should end up with. I just guessed on the countersink depth. Make sure you are consistent with what sides of the box get the holes at 3" vs. 2", so that the finished sandbox has bolts that aligned.


I worked in my uneven driveway, so I used a few cedar shakes I had as shims to level the boards. Also I used a carpenter's square to be sure the boards were at right angles. You can put the square on top like in the photo, or nest it against the outside of the boards to check for square.


Maybe there is a better way to hold the boards in place, but I used a small adjustable clamp to hold the boards square and level, while I used the 1/2" bit to drill through the holes in the 4x4s and through the boards.


Install the bolts (heads on the outside), nuts and washers (washers on the inside and outside). The bolts are flush with the lumber which is why we countersunk them. No need for little hands to get scratched up on protruding bolts.


Here's my finished box. I noticed that my box wasn't square. Measure from corner to corner, diagonally for both diagonals. The measurement should be the same, if it's square. If you look closely at the nearest corner, I screwed-up. That long front board, should be in front of the shorter side board. I had to redo that corner. It's really easy to make this mistake, so check twice before you drill and bolt!

Step 5: Building the sandbox seats

Okay, sorry, but I got in a hurry to finish this before the babysitter came back with the guys, and I forgot to take some photos. Basically I measured and marked the seat boards for cutting by resting them on top, and marking them where they meet the inside corners of the 4x4s.

I cut the 45 on my miter saw (I had to flip the board over to cut through all the way, as my 10" blade doesn't slide or cut through 12" boards at a 45. For all of these cuts, by the way, you could use a circular saw.

Next I took a single 3" deck screw (no pre-drilling required) and lined up the inside corner of my seat board directly over the inside corner of the 4x4, and drove a single screw to hold the seat in place. I did the same on the other end of the seat, and worked my way around all of the seats in that way.

You'll see that my boards did not line up exactly, but that can be fixed later, and I'll take the "hey it's just a sandbox" excuse at this point. Cheat it, and you can make it work by adjusting the boards.


Before adding the seats, I took apart the box and reassembled it near the final location (too heavy to move assembled). I then used blocks/shims to elevate and level the sandbox (going to stain all wood, including the bottom edge of the box, and I wanted it level before adding the seats).


As straight as the boards seemed to be, they still didn't meet well, as they all have there own slight bends and twists. So I took some 3" deck screws, and while squeezing the boards together, I screw gunned them into alignment.


Here's the result of that effort. Don't put them in too close to the corners, or you'll split the wood.


In addition to the screws above, I also put these 6" plates under the seat corners. The screw heads aren't flush with the plate, but nothing felt sharp to the touch for the kiddies. By the way, I have to thank Hans at my local Home Depot, who was nothing short of excellent. He helped me get all the right hardware needed for this project, based on a detailed plan that I brought along. He also was the one that suggested the 6" plates and the corner screws shown above.

In addition Hans suggested that I use 3" screws for attaching the seats, as he pointed out that you want 1.5" to be in the 2x12 below. I even invited Hans home with me to complete the build, and I think he would have taken me up on it, had duty not have called to help others. So my hats off to Hans (from the Netherlands) and Home Depot for a great hire. Thanks Hans!

Another thing I bounced off of Hans was what I've heard about checking the growth rings in the ends of the boards. As wood ages, it cups, and it cups inwards towards what would have been the center of the tree. As our seats age, we want them to cup downwards and not up. If they cup upwards water will sit there, promoting rot. Hans had a good way to remember which way the rings in the ends of boards should go. He said, "you never want your wood smiling at you". Thanks Hans.

Just as a time check, the above purchasing, transporting and building took me a day with a few breaks here and there.

Step 6: Completing the seats, sanding, and wood filler

Next I'm going to screw the seats down with the 3" deck screw, but wait, how will I know where to put in the screws if I can't see the board below. Well I measured in from the under side of the seat to the box board...


Then I transferred that measurement to the top side.


Knowing that 2" thick boards are really 1.5" think (that nominal vs. actual thing again), I made another mark. Measure twice, you can see I had too here. I measured and marked both ends of each seat board.


Next thing I did was snap a chalk line down the length of the seat boards between the marks.


Now that I have my center line marked right over the box boards (assuming the box boards aren't warped), I drilled in a 3" deck screw every 10" or so, seating them below the surface, to fill in with wood filler later. This thing is bomb proof! The seats are so sturdy that I can walk around all parts of the seats with no movement at all.


I then filled the cracks, screw heads, knot holes, and mistake holes with Minwax stainable exterior wood filler. I think the filler over the screw heads will stay put. I don't have high expectations for the corner gaps, but we'll see. I'm thinking they will crack in a few months, as this stuff always seems to shrink even though it says it doesn't, but perhaps it's better than nothing.


Next I used 60 grit sand paper on a 6" orbital sander to remove excess wood filler, and to round off all sharp corners and to knock down any sharp edges. I also sanded the seats at the 45s so that they met each other perfectly. Then I sanded every surface to prepare the wood for staining. Stain and paint like a freshly roughed up surface to adhere to.


And the final step before sanding... I used a leaf blower to blow off all dust and debris.

Step 7: Staining the sandbox

I had the tarp nearby as the rain was on and off, but I still managed to stain the whole thing in about 15 minutes. I used BEHR deck stain in their semi-transparent "Redwood" color. Goes on very quickly. Ideally one would get the cut ends of all lumber too, as that is where moisture enters the wood and causes rot and warping, but hey, it's just a sandbox...

Break for the day, What follows is from the next weekend. The rains came and so did the wife and kids.

Step 8: Getting the Sandbox into position

I marked off the spot for the box and then cut the sod up into squares with a spade and removed about 3 inches down.


After removing the sod, I leveled the ground with a level on top of a 2x4 to make it longer, and I used a metal rake to smooth/move dirt. I stole some gravel from my barn drainage project and added it just were the box perimeter would sit. I needed it to help level the pit, as one side near the rock wall, had compacted stone/stone dust that I couldn't dig through, so to build up the other end, I added the gravel, which I also think will help a bit with drainage and rot, as the boards will be sitting on the rock and not directly on soil.


Next comes the landscaping fabric. I overlapped two pieces by 4". You want your sand to drain and landscaping fabric will allow water to pass through into the ground, where as plastic will not. It also keeps soil, worms, weeds and other nasties from getting into your sand. This stuff comes in rolls from home stores, nurseries, and landscaping supply places.


Okay next step, you guessed it, 2 strong people are needed to move the sandbox into position. I'm going to wrap the landscape fabric up the sides about 2 inches and staple gun it in place, then trim off the excess. I've not done that yet. Then I'll backfill some dirt around the base of the box so that you don't see the fabric and staples. Many other sandbox plans online show the fabric being attached to the inside walls of the box. I don't know which way is better. I decided to go outside with it, as it seemed easier to deal with attaching and I liked the idea of the fabric barrier being sealed down around the box by the weight of the box. Perhaps someone can weigh-in as to why it's better to attach it to the inside, as I admit that seems to be the standard.


And now the part many have been waiting for. What kind of sandbox sand and how much sand! Well I spent quite a few hours researching this, as there is much debate about "what is the best sandbox sand" not only for quality, but also for safety. In the end, I rented the Home Depot rental truck and got 60 bags of their play sand, which I was able to drive right next to the sandbox, which made it easy to dump in. No wheelbarrowing needed, which would have been the case had I ordered a delivery of bulk sand from a landscaping company. That's a huge plus when you are talking about 3,000 pounds of sand and a hill down to the box from the driveway.


I was lucky enough to have Clark, a local college student, helping with a few projects this day. I cut the bags and threw them down, while he emptied them. Amazing how much sand is needed. Would you believe it takes 60, 50 pound bags? I have to say the sand was beautiful. It's just like our beach sand here in Northern New England. Silky smooth, light colored, and, well, lets just say I'm planning on getting my beach towel out with a cooler soon.


And here we have the end result. I can't keep this guy out of the sandbox. He loves it, and so do I. Make no mistake, the surround seating wasn't for him, it was for me. I didn't want a sandbox with tiny corner seats. I can lie down on the seats if I like.

My son and I spent the first evening lying in the sandbox looking up at the sky, which I had not done in some time. We saw clouds moving very quickly as a front was coming in. The sky was dramatic and fun to watch. We saw 3 planes very high up, leaving contrails, and I'm not sure how the Master Card ads go, but I have to say this story ends the same way, "time spent with your kid, when both of you are sharing a beautiful moment.... Priceless"


Ah yes, pure bliss.


I just happened to find a photo of my old sandbox. I loved it. Just goes to show that a pile of sand will entertain just as well. Here I had set up a construction site. They, we, I, am working on the foundation for some building to come. I remember staging this for a photo. Somethings never change. lol

How Much Sand do You Need for a Sandbox?
To calculate volume, it's Length x Width x Height.
Length is 8' for this box, width is 6' and I filled this box with 8" inches of sand. We have to convert the 8" to feet, because in the end we want to know the cubic feet of volume needed. So you divide 8" x 12" (one foot), which is .66 feet.

So 8' x 6' x .66' = 31.68 cubic feet (let's round that to 32 cubic feet)

Play sand comes in 50lb bags, and each bag is roughly half a cubic foot each. So 32 bags would fill the box 4", and twice that many bags (64) would fill it to 8". I only got 60 bags because the weight limit on the home depot rental truck is 3,000 lbs. 60 x 50 = 3,000.

If you plan to order sandbox sand in bulk and have it delivered, you'll need to order it in "yards" which is really cubic yards. To get cubic yards you divide your cubic feet needed by 27, and then round up to the next cubic yard.

32 cubic feet / 27 = 1.19 cubic yards

I think they only deliver in whole yards, so you'll need 2 yards (with lots left over), or settle for 1 yard. The delivery charge depends on your distance from the sand dealer.

What I paid for Sandbox Sand
The bags were $2.49 that day, so 60 x 2.49 = $150 (plus $20.00 for the truck) = $170

Total Cost of Project
$178.00 Materials
$170.00 Sand
$348.00 Total for this plan

Sandbox Sand Quality and Safety (I'm not an expert!)
It seems that the fine, dusty particles in sand can be inhaled, not ideal for young ones, and that sand dust contains silica (or sand is silica not sure), and that in California the play sand bags have to have a cancer warning on the bag. California seems to have more stringent warnings like this for many things. Our play sand bags did not have this warning, but I'm sure it's the same stuff. Studies have shown that in occupations where a worker is exposed to sand dust on a daily basis and for years (like sandblasters I suppose) that there have been links back to the sand dust for lung cancer and other lung problems. After writing this blog I found a link to the Material Safety Data Sheet (MSDS) for Quikqete Play Sand. Seems there are quite a few lung related issues, but these can been kept in check by 1. Keeping the sandbox outside, and 2. Keeping the sand moist and dust free prior to play.

After hours of research I couldn't find a concrete answer to the dangers of sand in a sandbox for kids. I did find forums of concerned parents, and much discussion ranging from people returning there unopened bags to Walmart and planning to start a riot with the Walmart management. I also found a few that claim the warnings are way over blown as kids aren't exposed all day long for years. And I found others that suggested parents ought not to worry so much and if they were worried about sand they ought never to go to the beach either.

I found one final article that summed it up best. Basically it said that the reason there are no definitive answers to the effects on kids is that it has and continues to be impossible to research with scientific accuracy, as there aren't any good test subjects. Worker (like sandblasters) are easier to research (They worked for X years, around X amount of dust and X amount of them have lung cancer that is from this occupational hazard). Imagine trying to study that in kids. Where would you start? My kid was in the sand box a bunch of times here and there back 10 years ago and now he/she has lung cancer... It's just too unscientific to track.

So like lots of things in life I think you have to do your own research, and then make your own decision based on your own risk assessment. For me personally I sent hours and hours in my sandbox as a kid and I'm still kicking. I even called 3 landscape supply companies and basically gave me mixed messages and seemed to be unaware of any issues. They do offer various grades of sands and you can ask them what's best for sandboxes. I suspect they won't give you a good answer. I also called a local sand quarry, they also seemed to unaware of any issues, and pointed me towards landscape supply companies to get a bulk deliver... A bit cover up? I don't think so. I think they truly don't know much about it. As sandboxes are not a big business for them, and they aren't doctors they are sand providers.

I got the stuff in the bag, vs. a bulk deliver (which would have been cheaper) because I could rent the home depot truck and drop it right into the box, and because the bags are called "Play Sand" and the bulk places couldn't accurately tell me what was good for play sand. I can tell you the sand was very dusty prior to the first rain. After that it has been more or less too damp to produce any dust at all. We are in a New England Spring so it rains a lot. Perhaps in arid climates or mid-summer it will be dusty again? I can always water it down if I wanted too.

Pea stone has been suggested as another option instead of sand. We well had a pea stone gravel patio (that we removed in favor of flagstone) and I can tell you it hurt my feet to walk on. I wouldn't want my kids playing in pea stone. Digging in that would hurt little fingers. And then I'm sure they would eventually stick the rocks up their noses! Maybe? lol

Okay, enough said. I add some links to articles later.
Berkeley Parents Network: Sand and Sandboxes--discussion about safe play sand

There's a company that makes "Safe Play Sand" but I'm not linking to them as I think they are bogus. First the price, $60 shipped per bag (I used 64, 50lb bags, that would be $3,840 for the sand). Yes, it's heavy and that's the reason the price is so high. I just think you are out of your mind if you buy this stuff. Second, and here I'll have to give a link to them. Take a look at this page. So on the left there are Google ads (fine for bloggers, and other personal sites, not okay for a commercial site a professional commercial site). And then see how they are trying to make more money with their Amazon Ads? Blinking Ads no-less. I just can't believe that a decent company that is genuinely concerned with your kids heath, would also pull out every additional web trick to make more money. Seems like a half-baked company to me. And I'm thinking their product is too. Lots of scare tactics on there too... This is all just my opinion, and they can weigh in if they like.

Can You Make Sand Castles with Home Depot Play Sand?

I never gave it much thought, but some parents are after sand that can be moldable, and apparently have gotten sand before that isn't. I've never heard of such a thing, but anyway, I just ran out back and did a test of our Home Depot sand (it's actually Quikete Play Sand). I've create all moldable forms for a complete test! LOL. Here you see a castle from a pal mold, a hand crafted castle complete with moat and tunnel, and a sand cake (someone was saying their daughters couldn't make them in their sand). Is this a sand cake? I have no idea! But there you have it. Very moldable. Of course I should have started by saying the sand was wet from a slight overnight rain. If you don't have rain, you have a hose.

More to come about covers, and cats! But that's all I can write for right now--Peter


Resources:
Bob Vila: How to Build a Simple Sandbox
Bob Vila: How to Build a Deluxe Sandbox
FamilyCorner: Building a Basic Backyard Sandbox
HandymanUSA: Building a Sandbox
Eric Stromer: Build Your Own Backyard Beach Sandbox

My Standard Disclaimer: This is what I did. This does not mean this is the best way, the right way, to building code, or even safe for your needs. So you are on your own with your project. I make no promises about the information presented here. I'm just a do-it-yourselfer, not a professional at all, sharing my story. So if something goes wrong with your project, you are on your own. Good luck, and have fun!

All content and photos, copyright 2009, Dover Projects.
_____________________________________________________________
My Other Articles

• Fix Double Hung Window Sash Cords
• How to Caulk a Bathtub
• Refinishing Pressure Treated Deck
• How to Build a Sandbox with Seats
• French Drain Design
• How to Build a Flagstone Patio
• How to Build Porch Railings
• How to repair a sliding screen door
• Replacing Broken Window Glass
• Barn Foundation Repair
• Knob and Tube Wiring - Replacing
• Recessed Kitchen Lighting & Design
• How to Drywall a Ceiling
• How Roofers Can Win More Jobs
• How to Insulate Basement Rim Joists
• How to Insulate an Attic Door
• Radiator Heat Reflectors
• Air Sealed Dryer Vent
• Toilet Tank Water Savers
• How to Check for a Leaky Toilet
• How to Clean Refrigerator Coils
• How to Make a Pet Door
• Energy Efficient Pet Door