I'm building an outdoor planter box(about 6.25"x6.25"x13 feet)that will
attach to the side of my house. The pine lumber was nominally 1x8,
ripped to 6.25" and with a true thickness of 3/4". How should I select a
screw or nail to attach the 7.75 x 6.25" end cap? I only have 3/4" to
stick the fastener into, which means that there is only 3/8" of wood on
either side of the fastener.
The concern is splitting. Number 7 screws, 1.5" cause splitting, even if
I predrill; #6 screws can work if I predrill everything and am careful
to make the pilot holes perfectly parallel to the face of the lumber.
With about 40 fasteners required, this is tedious.
The original box was held together with 1.5" staples. I don't own a
stapler, but renting one is a possibility. Any suggestions for nail sizes?
The screws aren't flat head screws, are they? If so the taper under
the visible head surface (sorry, I'm not up on screw terminology) will
tend to cause the wood to split as it's driven deeper. If you use pan
head screws you won't have that problem.
Yes, the screws I used for testing have flat heads, somewhat like sheet
rock screws. I could countersink the holes to prevent this problem.
Wouldn't I also have to countersink for pan head screws to get them
flush with the lumber?
A countersink is tapered, such as used for drywall and flat head
screws, and it creates a wedging action as the screw is driven home.
That is what's causing the wood to split. A counterbore for a pan
head screw would have a flat bottom. That provides a clamping action
and won't wedge the grain apart.
You could also use stainless steel finish washers and eliminate the
counterbore. The flat head screw would still sit proud of the
surface, but it might satisfy your aesthetic requirements.
Thanks for the excellent points. I had been thinking that if I don't
overtighten, a countersink would be okay. But with regard to the effort
involved, countersinking or boring would be equal.
At this time, I'm thinking of using a #4 pan head screw, 1.5 or 1-5/8
long, with a pilot hole the complete length of the screw and a
counterbore. Sound okay?
I prefer that the screw head be flush or below the surface.
Stick with #6's .....4's are too small. I would suggest a very
coarse thread like a drywall screw but not drywall screws
Sharp Point Thrd-Form Screw for Plastic 410 SS, Pan Head Phillips,
6-13 Thread, 2" Length
In stock at $8.34 per Pack
This product is sold in Packs of 50
Large Dia (Truss) Head Phil Sheet Metal Screw 18-8 SS, No 6 Size,
In stock at $10.63 per Pack
This product is sold in Packs of 100
but it's only 1.5" long
RIco's comment of the flat heads tending the split the wood is "spot
Even if you countersink for the head the splitting potential is still
there because of the shape of the underside of the head....its like a
The underside of a pan head is flat so even if you counterbore (that's
the correct term for a straight sided hole that the head goes into)
there is no wedging action to cause the split .
My suggestion is long (2") #6's with 3/32 pilot hole, use a 6" long
drill bit (the long length will help you with your hole alignment)
Use some scrap material to practice.....pine is pretty soft, you
might have to adjust the pilot drill size up or down.
Bigger pilot, less bite, screw might strip out
Smaller pilot, more bite, wood might split
The hole thru the end caps should be screw diameter not pilot size.
oops! I should have read furhter before posting redundant info
I'd use a 6d (I'd prefer a 7, but they're getting very hard to find any
more :( ) finish nail or if you don't mind the head even a 8d _box_ nail
would do. A box nail, if you're not familiar as a smaller shank than a
"common" of the same penny size for, as the name suggests, the precise
Although it won't make any long term difference in strength because of
the end grain, I'd use Type III glue or this is a place where even
urethane glues have a place for the waterproof nature as a moisture seal
to prevent mostly water wicking into the end grain.
Not on end grain. Glue joints rely on long grain to long grain
orientation for their strength. (*) End grain fibers can't form the
bond. It may hold for a little while as a mechanical bond, but even new
it won't have much strength and will certainly fail in the long run. As
noted, I use the glue for such applications as a moisture preventative,
not as a bonding agent. Pre-painting the end grain accomplishes much
the same objective but the glue is usually a little more convenient at
the time one is in the "putting it together" phase and wet paint is just
a lot more messy to use it at that time instead of glue. Dries more
quickly, too, in general, although the urethanes are pretty slow...
(*) Doesn't have to be parallel, but does have to be long grain. That
is, a cross-lap joint is fine whether the boards are joined end-ways or
at 90-degrees. Or the tenon cheek against the mortise side. But,
similarly to here, the tenon rail sides (top and bottom) even though
snug fitting, the glue surface there to the end grain in the mortise
don't contribute except for resisting racking forces and that only
I would put cleats in the corners and then use wood screws into the cleats.
This after gluing the all the involved wood surfaces.
It is important to consider the weight when this box is filled with soil and
water is added either by rain or irrigation.
This is also a consideration when attaching to the house
In reviewing some of the suggestions for using glue, I should have
pointed out that all surfaces have been primed with an oil-based primer
(Zinzer) to resist water entry into the end grain. (After assembling the
box, I may give the interior surfaces a second coat of the same primer,
followed by a latex finish coat.) I suppose the primer interferes with
the holding power of glue. I never considered glue as an option.
Also, I don't plan to fill the box with soil, but will use it merely to
hold container plants, so the weight of the box is not an issue and
attaching it securely to the wall is easy.
Don't say *even* if I predrill. You should always predrill if there
is the slightest chance of splitting, as there almost always is. Even
for finishing nails. With screws the hole can as big as the screw
shank, not counting the threads. With nails it has to be a little
smaller than a nail.
I can't envision the work, but even if you need to drill all these
holes, you may be able to speed things up. Make probably 4
attachments so the thing stays together. Then in the top piece of
each connection drill the hole for the shank of the screw or nail the
size of what is closest to the head. AIUI you can make that hole so
big you can push the screw in with your finger, but of course not so
big that the head of the finishing nail will go through. Drill all
the holes of that size. Then change bits to a smaller one that will.
Hold the top piece in place, drill a hole, and screw or nail the
pieces together. Same thing in a second place, maybe caddy-corner to
the first one, and screw or nail the the pieces together. Maybe go on
to another piece then, or finish the one you are working on, but at
some point, you'll be able to just drill, drill, drill, drill, then
come back and nail, nail, nail, nail, (or screw etc.)
IIUC, they used a stapler because it was quick and easy, not because
it was good. Note that it is falling apart now. That's what often
happens with staples. Not that there isn't a place for them in
quality work. I just can't remember where that place is.
(But I forget a lot. Upholstery maybe; temporary attachments; a
portion of installing some convertible tops, in the tack strip above
the rear window, for cars that attach there. My first top said to use
carpet tacks iirc, perhaps because consumer staple guns were rare in
1970. The pros use a staple gun; and some others.) BTW, a standard
electric staple gun is only a dollar or two more than a manual staple
gun these days. Quite amazing. I forget the price, but even a cheap
guy like me thought it was cheap. I think I bought it to attach cloth
to wood in a situation where I was working alone, and couldn't hold
the cloth in place while I hammered in tacks, because that would all
take three hands. With the electric stapler, 2 hands were plenty. I
felt like a dynamo. Just don't point it at anyone.)
Thanks for the excellent "production line" tips for speeding things.
The box was installed when the house was built in 1968. So I can't
really complain that the staples didn't hold up well over the decades.
When I bought the house in 2000, some of the pieces had separated, but
just as important, much of the inside wood was rotted. I'm embarrassed
that it's taken me seven year to replace it, but now that I'm about to
paint the whole house, might as well do everything right.
This has been a great thread and I learned a lot about screw geometry.
Thanks to all who have contributed.
I have one question, directed both to the OP and the other
AIUI, this is to be an outdoor planter box.
Why not a wood more resistant to the kinds of damage that
dirt and water in a planter box will do to wood?
Seems to me the labor part of building this (as evidenced by
the OP's iitial question) is the hardest part. In my experience,
with pine, you are going t d this agan in 5 - 7 years.
Why not use cedar or cypress or even redwood?
Or a composite? Or a really tugh South American wood?
Sure, its more expensive for materials than pine,
but ou don't have to re do it.
Pine, mainly because it's easy to get in the length (13+ feet) that I
need. Initial expense was not a factor.
The box I'm replacing was almost 40 years old and made of what appears
to be pine; considering that the cheap builder used pressed paper for
the fascia and soffits, I can't imagine him using anything but the
cheapest for the planter box. Had the inside been maintained better, I'm
sure it would have held up much longer despite being pine. The
separation at the corners where the staples pulled out could have been
To improve weathering capability, I'm double priming all surfaces (and
edges and ends)with an oil-based primer before assembly. I'll apply a
latex finish coat. I don't plan to put soil in the box; it will be used
mainly to hold potted plants. I still have to figure out how to place
drainage holes for rain.
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