New project for work

[Stigmorgan]

So the headteacher has asked about installing some benches under a shade sail that will blend in with the woodland theme I've been creating on site, my first thought is to keep it simple and use sleepers, I can make 2 benches from 3 sleepers if I cut 1 into 4 pieces at about 600 long and concrete 300 into the ground, this should give a seat height around 400 above ground, my dilemma is which sleepers would be best, they are all 2.4mX100mmX200mm
Treated brown hardwood
Treated brown softwood
Treated green softwood or
New untreated Oak
My personal preference would be oak but will it last being untreated and concreted into the ground?
Cost isn't an issue, I've given the school my "quote" based on using the Oak sleepers which are the most expensive at £49.95 on the website but the company have always given me a good 15-20% discount and free delivery when I order stuff for school as they are literally across the road

 

[HOJ]

Just a quick observation, I know you will know, but if I were making a seat, in this environment, I would be cautious using Oak, as it will release Tannins and treated timber may leach out any treatment/colour, when it gets wet, and consequently run the risk of staining etc.

There are regulations for "playground furniture", and the materials allowed to be used, along with maintenance conditions, whether they would apply in this case I don't know, but we have to have inspections on the gear we have at the village hall public play park.

 

[Katomi woodsmith]

We used sleeper on our century project
The kids were forever getting tar on their cloths
Be warned

 

[akirk]

best wood might be something like greenheart or opepe or ekki (though sharpen your chainsaw!)
they are all used as marine timbers for dockyard gates etc and are fairly indestructible - I have offcuts for sitting around the firepit and they happily sit out in all weathers and will outlast me!

 

[paulm]

I made some simple benches from treated softwood sleepers for the woodland a few years ago.

One sleeper per bench, just dug into the ground and lasting very well.

Recessed the uprights into the tops, nice tight joints to help reduce racking, and secured with timberlok screws at an angle from below, nice and solid

 

[nickds1]

I used to make green oak furniture for exterior use for the National Trust. We also used kiln dried oak for more complex work like the Lutyens and Clem Churchill benches at Sissinghurst and Chartwell. Sissinghurst gets about 200,000 visitors a year, many gravitationally challenged, and they survive that!

Green oak is heavy and hard to work with, but superb for rustic exterior benches & tables etc.

Never any problems with leaching of tanins etc. just need to understand seasonal movement.

Oak is the National Trust's wood of choice for exterior furniture.

https://www.ukworkshop.co.uk/threads/post-a-photo-of-the-last-thing-you-made.81798/post-1492484

 

[niall Y]

Greenheart survives by being a pretty noxious timber, One certainly wouldn't want a splinter of this especially not in ones rear end as they can go septic.

 

[Stigmorgan]

I made some simple benches from treated softwood sleepers for the woodland a few years ago.

One sleeper per bench, just dug into the ground and lasting very well.

Recessed the uprights into the tops, nice tight joints to help reduce racking, and secured with timberlok screws at an angle from below, nice and solid

View attachment 196064

This is exactly what I have in mind except they will be 2.4m long and heavily concreted in, the kids will likely climb on them more than sit on them and the ground has only had 5months to settle since the newbuild was completed, being under the shade sail has the bonus of keeping the worst of the weather off the benches

 

[Stigmorgan]

Just a quick observation, I know you will know, but if I were making a seat, in this environment, I would be cautious using Oak, as it will release Tannins and treated timber may leach out any treatment/colour, when it gets wet, and consequently run the risk of staining etc.

There are regulations for "playground furniture", and the materials allowed to be used, along with maintenance conditions, whether they would apply in this case I don't know, but we have to have inspections on the gear we have at the village hall public play park.

Those regulations apply to equipment like climbing frames and ropes rather than seating and tables, all of our trim trails and adventure playgrounds are inspected annually, they've never wanted to check our picnic tables and benches.

 

[Blister]

If you do use softwood beams I would give the ends that are going into the ground
several coats of Bitumen up to ground level , It will help stop rotting.

 

[mccpe]

Definitely oak. I’ve used untreated oak for a couple of garden fences specifically because there’s no need to treat them and they are still perfectly good after 10 years.

I think your only issue might be having to concrete them in. The concrete will retain moisture so the legs will end up being damp, and will ultimately rot. It might be a good idea to add plenty of rubble to your mix so that you end up with something pretty porous. It sounds like you need the weight of the concrete rather than ultimate strength. Also consider using hydraulic lime (NHL 3.5) rather than cement. It will set just as quickly, but will not retain moisture.

 

[Stigmorgan]

Definitely oak. I’ve used untreated oak for a couple of garden fences specifically because there’s no need to treat them and they are still perfectly good after 10 years.

I think your only issue might be having to concrete them in. The concrete will retain moisture so the legs will end up being damp, and will ultimately rot. It might be a good idea to add plenty of rubble to your mix so that you end up with something pretty porous. It sounds like you need the weight of the concrete rather than ultimate strength. Also consider using hydraulic lime (NHL 3.5) rather than cement. It will set just as quickly, but will not retain moisture.

Correct the concrete will be more stabilisation, the ground is very well draining but most of the leg will be in the topsoil layer (300mm-ish) so will look into getting the lime instead of postcrete and paint the ends with some bitumen (i have a tin of roofing felt adhesive somewhere)

 

[okeydokey]

Is 2.4m long without a central support ok would a middle leg help?

 

[HOJ]

Don't get me wrong, I'm not adverse to using Oak, that's pretty much all I work with, I make quite a few Oak garden seats and benches, but use KD Oak, and don't have the issue of the Tanins washing out, whereas when I've used green or air dried Oak in my construction builds, for a while the leaching is very evident.

But as its under a cover this may not be the case.

When I plant posts in the ground I wrap a bit of DPC/plastic around them so at least an 1" of it is above the soil line, certainly helps to stop the rotting at that point.

I had to replace my 8" Oak front gate post last year, had been there since 1989, as it had given up, but that's had a 12' 5 bar gate swinging on it all this time, so longevity for a bench wouldn't be a worry.