DIY wood frame greenhouse timber question

[gardening_gal]

If a wooden frame was made the shape of a apex shed but covered in polytunnel plastic, should all the timber used for the framing be treated?

Could untreated timber be used for the roof trusses since no water would be near them or is the likely humidity and condensation liable to rot them quickly? I'm not after anything that will outlive me but I'd like it to last more than a season or two.

Just wondering if treated wood could be used for the wall framing and untreated for the roof (simply down to cost/availability).

I should add the timber wall frame sections from an existing shed that I'd be utilising are made with only 44 x 28 wood so anything new added couldn't be too heavy otherwise I'd have to start adding extra supports etc. which then means a lot more cost.

This is why I'm wondering about treated versus untreated. If the framing was solid 3" x 2" then I wouldn't be concerned but as it is a lot thinner I don't know if treated/untreated is an issue or not?

Also, would the usual polytunnel hotspot tape stick to wood? I'm thinking the roof ridge wouldn't be kind to the plastic.

I know I could add poly pipe hoops as a roof support instead but due to aesthestics in the garden, I'd prefer it to have the apex shape.

Thanks in advance for any thoughts.

[Stan79]

Is this as well as, or instead of the greenhouse you bought?

[gardening_gal]

As well as. Originally the shed was being dumped but I've now decided to repurpose what I can from it. That's why I want it to stay as an apex shape, it will be sitting beside the greenhouse so it will look as if it is in a line if you see what I mean. The gate will be between the two but the eyeline will still be the same.

[nickdub]

If you do go with untreated timber I'd advise giving it a coat of ranch paint before putting it in place to help waterproof it - costs about £1 a litre if you get it in the sales and does a pretty good job - try to avoid the hideous bright orange colour option if you or your family are of a sensitive nature.

[gardening_gal]

Had to Google that Nick, never heard of Ranch paint. Never fear, I'm definitely a neutral kinda person.

[veggiechicken]

If I had an unwanted shed I'd keep the shed structure/frame, Lower the sides to raised bed height and put raised beds along every wall and back - like a GH layout.
Maybe cover the frame with netting or wire and turn it into a fruit cage or pea/bean cage.

A walk-in fruit/veg house. All I need is a redundant shed.

[Stan79]

Could you add pipe lagging or old carpet to the top of the frame to protect the plastic?

[bikermike]

I would treat all outdoor timber as a matter of course. Especially in a greenhouse where it may well be damp, especially where it could be a condensation trap.

In particular, I like to soak any end-grain (ie where you cut accross the timber) in preservative, as the wood will wick moisture up the grain.

I have to say, I like the idea of keeping the shed as half-greenhouse, as i end up with loads of stuff (pots/trays etc in mine

[gardening_gal]

If I had an unwanted shed I'd keep the shed structure/frame, Lower the sides to raised bed height and put raised beds along every wall and back - like a GH layout.
Maybe cover the frame with netting or wire and turn it into a fruit cage or pea/bean cage.

A walk-in fruit/veg house. All I need is a redundant shed.

That's sorta what I was thinking, using the half decent planks round the bottom like a wee wall but covering the rest in plastic to let in light. A lot of the upper planks are rotten as is the roof but the frame can mostly be used as long as I put in new rafters. At the moment the shed has roof supports going from end to end rather than the more usual side to centre configuration. That's probably why it sagged so much, useless thing.

I figured it would be a good potting area or a place for the kind of plants that can go on shelves in pots before transferring to the greenhouse maybe.

Could you add pipe lagging or old carpet to the top of the frame to protect the plastic?

I did think about pipe lagging, I have some left over from another previous project so I might be able to use that in some way, It's that grey circular stuff, very thick but I'm sure I could cut it down.

I would treat all outdoor timber as a matter of course. Especially in a greenhouse where it may well be damp, especially where it could be a condensation trap.

In particular, I like to soak any end-grain (ie where you cut accross the timber) in preservative, as the wood will wick moisture up the grain.

I have to say, I like the idea of keeping the shed as half-greenhouse, as i end up with loads of stuff (pots/trays etc in mine

That was what was bothering me tbh. The polytunnel I had to shorten to fit into this garden when I moved had to also be home to gardening equipment. I'd collected a great deal of pots, trays of all sizes etc over the years and they were just stored in boxes for lack of space. At least if I repurposed the shed it can be a combined storage and seed starting area etc.

It sounds like I'm just as well just getting some new treated wood though rather than faffing about trying to protect untreated wood. I dont think I need much but my purchase options are limited right now for obvious reasons and I'd have to pay more geting an order delivered from the likes of Wickes rather than using my local builders merchant, which is why I was trying to save a few bob by buying untreated. Probably not cost effective in the long run that way though.

Thank you all.

[nickdub]

Had to Google that Nick, never heard of Ranch paint. Never fear, I'm definitely a neutral kinda person.

It's more or less the standard for fences etc these days, B&Q sell it in up to 20 litre tubs or you often see 5L ones in cheapo shops - only one downside to it I've found, and that is any left in the container won't stand frost. If you have some spare to store over winter it has to go in a frost free place.

[gardening_gal]

A month or so ago I bought some 3m lengths of treated 6" x 2" decking joists, they were on clearance. I figured I'd use them either as a base for a new shed or I'd make raised beds out of them.

It dawned on me a wee while ago (I do seem to be lacking in the common sense dept these days ) that I could rip them on the table saw and make my own rafters. So that's what I have just done. I sacrificed 2 boards but I still have more than enough for other projects.

So, new question is - the wood was treated but since I cut a 6 inch wide piece into narrower strips, I obviously have long sides now that are bare. I found a tin of yacht varnish as well as some green Ducksback fence paint in the other shed. I'd rather keep the wood lightish coloured, would the varnish be ok to use or not????

I could buy something else, I just wondered if I could use what's here.

[nickdub]

I'd use the yacht varnish, but dilute it down a bit with white sprits so it soaks in to the wood more.