Another planter, another set of questions

[baldpate]

Just had a garden makeover, and LOML wants a largish planter in the same style as these on ebay
http://www.ebay.co.uk/itm/160645815...eName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Unfortunately they don't offer one in the dimensions she wants (about 4' wide x 8" internal deep x 18" high), so in a rash moment I said I could make one like that. As you can see from the ebay images, the structure is basically a simple one : a set of identically-sized rectangular frames which are stacked one on top of the other to the required height; each level of the stack differs only in that the corner joints are oriented differently - alternating clockwise and anti-clockwise.

The material I shall be using is 44 X 70mm pressure treated planed timber, so to get the height I want I shall need a stack of 7 frames (7X70mm = approx 19"). However, I have some doubts about several aspects of the constructions, and I could use some advice. I'm hoping the planter will last at least 10 years, preferably 15+ years:

a) The four corner joints on each frame.
I'd prefer not to get involved in cutting 28 M&T joints; but at the other extreme I don't like the idea of just using screws to reinforce a butt joint (ugly exposed screwheads, and I'm not sure it's strong enough). I'm quite happy to use screws if they aren't visible, and the result is strong enough. I was however thinking of using dowels, 2 per joint, perhaps the large-size Miller dowels (oak, glued with PU glue). Would that be strong/durable enough?

b) Joining the stack
At the moment I'm thinking simply of using 120mm screws to screw each frame to the one immediately below (say 8 per frame). Would that be strong enough on its own? I could glue each frame-pair with PU glue, of course, but would that add anything over my desired lifetime (I'm unsure how long I can expect PU glue to last in something like a planter).
PS the planter will be lined.

I don't want to change the basic design, as my wife likes that look, but any suggestions how I can achieve it and make it strong/durable would be very welcome.

Thanks

Chris

 

[dickm]

Depends how soon the Boss wants it! Screwing each layer to the one below would be best, but nailing would be equally OK for all except the top layer. I'll bet the one shown does not have anything other than butt joins for the corners.
Not a mortice and tenon within miles!

 

[Woodchips2]

Hi Dick
I dowel the bottom layer and screw the base on, then just screw each subsequent layer to the one below and nail the top layer. I've seen commercial ones just stapled together!
Regards Keith

 

[DeanN]

You can see from the pictures that the top layer has its mitred corners screwed together, and I would guess the layers beneath are screwed from below - i.e. its made upside down, with the bottom layer/base last.

 

[Chrispy]

Hi Chris
I made some a bit like those much smaller section of wood 30mm x 40mm approx apart from screwing the layers together as you go I drilled the corners for a M6 all thread bolt top to bottem to secure the corners, at the moment there is just a nut at the top but at some stage I intend to screw finials onto the ends of each bolt.

 

[baldpate]

Many thanks for your observations & suggestions.

 

[baldpate]

*** FURTHER QUESTION ***

Hi again - I'm resurrecting this thread because I have another question, if you don't mind. This time, regarding the glue to use for the dowels.

I'm about to glue the pair of dowels (12mm diameter, ordinary grooved dowels, not the Miller ones I was originally considering) into the first corner of the bottom frame. I have available both Polyurethane glue and Titebond III. My original intention had been to use PU, but now I'm reconsidering (I hate using PU!).

In your opinion, which would be better for long-lasting resistance to the conditions the planter is likely to encounter? If there is no really significant difference, I'd rather use the Titebond.

Thanks again.

 

[davem62]

hi remember to treat all cut ends with end grain preservative to make sure it lasts

 

[brianhabby]

I have had excellent results on long term outdoor projects with PU glue and not so much experience with Titebond III.

Having said that, I agree with you that PU glue can be messy, especially for something like dowels, so maybe Titebond III is the way to go. It's supposed to be waterproof so it should be okay and certainly a heck of a lot easier to clean up.

Hope that helps - I'm sure others with more experience will be along with their advice too.

Best of luck with it

regards

Brian

 

[Woodchips2]

I don't use glue with the dowels because I see them as an aid to accurate assembly rather than relying on the dowels for strength.
Regards Keith

 

[baldpate]

Hi again,

just to say thanks for all your useful advice, much of which I used in the build - now completed. Here's how, in case anybody is interested.

a) I dowelled the bottom frame with 12mm Iroko dowels, glued with Titebond III. 2x100mm dowels at each corner. I understand Iroko is pretty resistant to rot.
b) All intermediate layer frames secured with 2*120mm screws at each corner (don't know now why I didn't do this on the bottom frame too - so much easier!). I sunk the heads about 15mm below the surface, then plugged with more of the same Iroko dowel as used on the bottom frame, again glued with TitebondIII. These layers look exactly the same as the bottom one, which uses true dowels - and I suspect are just as strong.
c) Top frame mitred, glued with PU glue, then each corner reinforced with two 1/4" oak keys (again PU). Mitring was a pain - my SMS is cheap and not accurate enough for mitres straight off the saw, so lots of trimming with block plane required to get good glueable mitre-joints.
d) All the cut end-grain was treated with Cuprinol decking end-grain preservative (thanks davem62, I'd overlooked that one!)
e) The whole structure was screwed together, from the bottom upwards (as DeanN indicated), again with 120mm screws. I counter-bored the expose vertical screw holes in the base layer to about 15 mm and filled then with hot-melt glue : I'm hoping this will keep out the water and other nasties. I'll let you know in 10 years time, if I'm still around .

The end product, although largely screwed together, has no exposed/visible screw-heads. The construction is probably overkill, and it certainly didn't cost less than the commercial offering, but I'm hoping it will last a lot longer. And LOML is pleased, so a result there !

 

[doorframe]

Chris.... got some pics?

Planters are a great way of using up offcuts (especially if you haven't got a wood burner), although your's is obviously a tad grander than most planters!

I made some a bit like those much smaller section of wood 30mm x 40mm approx apart from screwing the layers together as you go I drilled the corners for a M6 all thread bolt top to bottem to secure the corners, at the moment there is just a nut at the top but at some stage I intend to screw finials onto the ends of each bolt.

That's a great idea 8)

If you want so sell them (on ebay, for example) anything that sets them apart from the rest is always good.

I made some wheelbarrow planters a while back, and they sold ok, but were a bit too small. The larger ones seem to sell better.

Roy