Building slab ash table for outdoor usage

[Mark Wedel]

I've done quite a bit of woodworking at a hobbyist level, but this will be my first project of this nature. A lot of this is mostly a sanity check of my thoughts.
As background, last year, an ash tree in my front yard was taken down due to disease. I kept the wood - I slabbed out the main trunk with a chainsaw mill and kept the smaller pieces (6-12" diameter range) for bowl turning. The slabs have been drying for almost a year (picture below). The slabs are ~7' long, from 15-24" in width, and sawn to 8/4 thickness.
I don't have need for an indoor table, but could use a couple nice outdoor tables. I know ash is not an outdoor wood, but I'm in California, where it doesn't rain in the summer, and even in the winter, it might rain for a bit, and then things dry out. I figure with a good weatherproof finish (suggestions - I still want to be able to see the grain), this should be good for many years.
I had thought of making 1 really big table, but 2 smaller ones seems more manageable to be able to move around, and also flexibility in how I want to arrange it (one long table, L shaped, etc). I have 6 decent slabs, so I'm thinking 3 slabs/table should give a reasonable width - the slabs have a bit of an hourglass shape - swell at the bottom, but also at the top where it branched into 5-6 branches, so I know I'll loose a bit of width when assembling these together. My thought is to use my track saw to get a relatively straight edge for joining. The top pieces on the stack might be useful for infilling something - I mostly kept them because why not, but I also think I need to play around with positioning of the slabs to see if I could do something to use the curves and minimize waste. But not sure who I'd go about making non straight cuts that are tight enough to each other for good joints.
Based on the sagulator, these should have no problem holding whatever weight might be on them, even if the only supports are the end of each table.
Any other words of wisdom?

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[John Kananis]

Mark, you're looking at a couple more years before you can start thinking about using that lumber. It's going to still be pretty wet and will warp like crazy, won't take finish, etc, etc. As far as finish, you're fighting the elements and the gray monster that eventually eats most (exterior) things we make. You have to be diligent with outdoor furniture or it all winds up the same color.

[Chris Groer]

Mark - was the tree already dead? I'm in TN and had a huge ash felled a few years ago due to emerald ash borer here. My tree had been dead for some time and was already quite dry so I used it almost immediately to build a few things and have experienced no issues (I did not check the moisture). I built my son a lacrosse goal out of it since I had so many big thick pieces. It has survived almost 2 years in our weather with a couple of coats of spar varnish FWIW

[Jimmy Harris]

The real problem with ash and the outdoors isn't so much water but bugs. Bugs love to eat that wood. Ants, termites, whatever. Now a good, thick finish will protect it, but being out in the sun and elements, you'll have to replace or repair it often. This isn't to say it's not doable. Just that since it's not ideal, it'll take extra care and maintenance to make it last. Though, this doesn't sound like project that you need to last forever, so maybe that's an acceptable risk for you.

As for jointing curved surfaces, that's going to be tough. Not impossible. Just tough. You'll probably want to do that with hand planes or spokeshaves and go little by little. You could still do the majority of the work with a band saw or jigsaw, but leave yourself some room to creep up on the final fit. That's kind of why everyone tries to joint straight pieces. It's just so much easier and quicker.

Get yourself a moisture meter and record the moisture of the wood at various spots for a few months. Keep a log of it's progress and wait for it to stabilize before attempting this project. Ash trees have a much lower moisture content than most, so the wood does dry out quicker than most other species. But why take chances on a guess when you can know. Plus they're worth owning if you don't already have one.

[Bradley Gray]

If you build a table with space between the planks the moisture content will not matter as much.

[Richard Coers]

Ash wood is not suited for outdoor purposes. It is rated as perishable and will not last long if in contact with the outside ground. It is slightly more durable with regard to decay, but is not particularly rot-resistant or insect-resistant, hence its suitability for indoor purposes.
https://www.wlwest.co.uk/species/har...or%20purposes.

[Mark Wedel]

I don't plan to have it in contact with the ground. I'm not sure what I'd do for legs - wood with epoxy at the bottom, metal, or something else. As such, the table top itself should stay pretty dry (I could even cover it in the winter, since I'm unlikely to use it at that time of year - I usually put away the chair and other related items in the winter just to help preserve them some)
Conditions out here are pretty kind to wood - I've had untreated 2x4 (cheap ones from HD) sitting outside for supports, so getting rain, sun, whatever, and while they weathered, no rot or other damage even after 5 years. So I'm thinking if I take the time to treat this, I can hopefully get 5 or so years between need to apply a new finish.
The tree was not dead when removed - the upper branches were dying, and it was a matter of time before the entire tree was going to be dead, so the city decided to remove it vs coming out every few years to remove the dead branches. For some of the smaller branches I've turned into bowls, this can provide an interesting contrast in color.
Wood out here dries a bit faster - warm summers (~82F) and year round low humidity helps out - which also helps reduce rot of wood in general. When I built my anarchists workbenches, the wet 2x6 douglas fir dried out in a few months. Taking a measurement right now of the ash, it is about 15%.
I hadn't though much about bugs - real worry out here would be termites.
The idea of not even joining them but leaving gaps is an interesting though. picnic benches are built that way out here (usually out of redwood 2x4s), so not much different than that. It certainly makes the build easier.
I'm not looking to start this build tomorrow, but more at the information gathering phase. If I had an indoor use for it, I'd probably go that route, but I also have a slight concern if it currently has any bugs in it, I really don't want to bring those inside either (and I don't have a good way to sterilize wood that large). so that was part of the thought of using it outdoor - might not be ideal, but if it works for a decent number of years, it might be the best use I can put to that wood.

[Richard Coers]

Direct UV light is never kind to wood or wood finish. White wood even has more resin in it than ash, and ash is a ring porous tree which really hurts its rot resistance. You can justify it all you want, but science doesn't lie.

[Joe Calhoon]

Ash might hold up better than you would think outside. Especially if all heartwood. A few years ago I did exterior and interior millwork doors and windows for a 120 year old narrow gauge passenger coach restoration for the railroad museum here.
The original was all heartwood ash and totally outside for all those years. Sitting since the 50s totally uncared for. Some of the horizontal sills were rotted but other than that the wood itself was not that weathered. Pictures of an original door and the replacement we did as an exact copy. Tried to use mostly heartwood but limited by quantity on material for the job.
I think the RR industry used ash for the outside durability and shock resistance as these trains are pretty rough riding. Just my speculation though.
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[Richard Coers]

Since he's talking about a slab table, pretty sure it won't be all heartwood.

[Cameron Wood]

This table has been outside for 2 1/2 years- Norcal, mostly under an eave but gets wet and pretty full sun. DF, spar varnish, holding up well. Rubber blocks on the feet.


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[Holmes Anderson]

Ash wood is not suited for outdoor purposes.

Respectfully disagree. Ash is commonly used in boat building in North America. Not as rot-resistant as teak or white oak by a long shot but still usable.