Hi,

I’ve, perhaps unwisely, agreed to build some much needed outdoor storage beneath Geordie Junior’s treehouse. It’ll be used to store outsize items that are too large to store in the shed without me having a hissy fit everytime I want to get the bike out.

Anyway, I was all set to construct a box with doors independent of the treehouse’s legs, but Mrs Geordie (ever the form over function) insisted I make full use of the space which has meant enclosing the base of a fairly large cherry tree trunk. True, it does give us more room, but as the trunk effectively comes through the roof of the box, rain can stream happily in to the enclosure below.

Has anyone got any suggestions what I could use to stop the ingress of water? I’ve toyed with the idea of entering the words ‘rubber’ and ‘skirt’ in to Google, but I think the Bank police would be down on me like a tonne of bricks.
Cheers,

Andy

You’ll have to do it in a hoop [or whatever a square hoop is called]

You want something similar to a kayak spraydeck I reckon. Neoprene with a rubber shockchord. You’ll have to get the tree to step into it though… 😀

From http://www.thetreehouseguide.com…

Branches and trunks passing through the treehouse

Along with a flat roof, this is one of the things that seems a good idea at the time of design but once in place can be a real headache. Allowing a trunk or branch to flow through the house looks great but brings with it two problems; water flowing down the branch and movement. There are several solutions but to get a satisfactory result may require some compromise. It is unwise to fix any part of the roof or wall to a through-branch because it will move in different directions to the treehouse’s floor and could cause structural damage over time. Branches and trunks tend to channel water in the rain. The simplest way to tackle both movement and water problems is to cut an oversized hole in the wall or roof and, importantly, another oversized hole where the branch or trunk exits. The size of the holes needs to be determined carefully so the walls/roof are not touched even in strong winds. This way the branch has space to move and water can flow through and out the other side.

A logical upgrade to this system is to use a rubber collar system around the point where the tree enters the house. This method sometimes works very well, but is notorious for small leaks because the rough texture of most trees does not allow a perfect seal. You also need to adjust the collar each year as the tree grows. You may decide to accept a small amount of water coming in as a trade-off to the beauty of a part of the tree contained in your treehouse.

Looks like you should be searching for “rubber collar”

Flashing Tape?

I was thinking something along those lines kayak, but not sure where to source the raw materials. Are you actually suggesting a spraydeck, or is there a builder’s equivalent?

Ta Ormancheep – good call. Will try that too.

Not sure how that would work Nobby. Are you suggesting taping it across the boards and bunching it round the trunk to try to seal the gap?

Would expanding foam do the trick? You’d probably have to fashion a temporary platform under the hole to stop the foam falling through while it set.

Yes, I reckon a modified spraydeck may actually work. Of course you’d have to have it take-off-able… But maybe you could get enough pressure on it for a fairly decent seal.

Also, look into neck seals for drysuits. There is a chance you could use one of those, cut to get it to fit and then re-join using rubber adhesive.

It would form a tightish seal and allow a little movement. You could also cover it with neoprene to reduce the effects of weathering perhaps.

This Place reccommends using a car or truck inner tube as the sealing skirt. Would work well I’d have thought..

Also, I was thinking perhaps if you did have some sort of waterproof ‘skirt’ around the trunk, I wonder if it would stick to the tree with silicone sealant?

This may buy you a while in terms of movement, though I’m not too sure if it would damage the tree, but I wouldn’t have thought so.
Whether or not it would stick is I suppose the issue..

Not sure how that would work Nobby. Are you suggesting taping it across the boards and bunching it round the trunk to try to seal the gap?

There’s wide versions of it that I’ve seen used to seal where a soil stack vent pipe exits a flat roof. It’s very pliable – they do rubber versions too – so you can wrap it around the tree forming an inverted ‘funnel’ shape. Possibly even shave a small groove into the bark for the top edge to sit in then another strip over the top of that.

Thanks for all the suggestions guys – and the links. Appreciated.

cherry grows relitively quickly doesnt it ?

Presumably your box is going to be open at the bottom, for the tree trunk to pass through again, so why not just let the water run down the trunk and back out of the bottom?

Make a large cylindrical space around the tree trunk and box it in. Seal that, then build around it. You’ll end up with a “doughnut” shaped storage area but at least it’ll be possible to keep it dry and the tree will have room to grow and move.

Would it not make more sense to box inside the box arround the tree trunk, if you do this 30-50mm from the current edge of the trunk it would give the tree growing space and allow the water to drain down the trunk to the ground.

[edit]druidh said it better and quicker than me[/edit]

what is going in the box that needs to be bone dry ?

Make a large cylindrical space around the tree trunk and box it in. Seal that, then build around it. You’ll end up with a “doughnut” shaped storage area but at least it’ll be possible to keep it dry and the tree will have room to grow and move.

That’s what I would do. Let the water run through.

Self amalgamating tape around the tree to avoid damaging it and to provide a rubber seal area to join too, then neoprene/ rubber sheet, / plastic whatever fits the bill & you can get, to fashion the skirts or spraysheild ideas, more amlagamating tape to hold that to the tree & simply glue the split in the skirt with evostick.

Possibly even shave a small groove into the bark

won’t that kill the tree? Or is it a myth?

A couple of things that may be worth taking into consideration while thinking about all these suggestions –

A cherry tree will be continually growing both upwards & outwards. If you fix anything to the trunk it will move upwards over time and also need space to expand as the trunk does.

No matter how well you seal the gap around the trunk at the top the boxed in section of trunk will still continue to ‘breathe’, giving off water vapour. Over a period of time this will make the atmosphere in the box humid and will result in anything that could rust going rusty.

Decktight as in used on all our industrial roofs. You’ll have to cut it tho, open it up an reassemble around the trunk. Come in many sizes.

trail_rat – a mahoosive bean bag.

Grizla – it’s more the drips from the overhanging treehouse floor that I need to seal.

druidh and rusty mac – Agreed. But that would require more wood and re-configuring what I’ve already got. Not saying it’s not the right answer, but assessing quick fixes first.

tinsy – yes, this seems like a good compromise. Just need to choose the materials carefully. The tree is mature, but as mentioned by many, it would be preferable to allow for growth and movement.

wrightyson, do you have a link please?

This is all I could find on decktight seals, it looks OK but not sure how well you can re join it after cutting.

without me having a hissy fit everytime I want to get the bike out.

It’s not just me then?

Big plastic dustbin lid, cut in half, make opening for trunk, reassemble in situ with flashing tape about a foot above the hole.

As mentioned, best to leave the current hole open to allow air to circulate.