Wood Treatment - cedar greenhouse

[robsut]

I have a cedar wood framed greenhouse which is approx 40 years old and which is now showing it's age! The main frame is in good condition and the timber is solid. All that is need of is no more than a good clean and a preservative applied. The problem is that on the roof glazing bars and the surrounding frame, water has started to penetrate into the wood making it soft and causing moss to grow under the glass. Over the next few weeks if it is dry, I hope to remove the glass from the frame a section at a time, remove the old putty and thoroughly clean the rails and then put the glass back in. Before I put the glass back in, I have a few questions: -

1. Treatment of the wood - I would like as to treat the wood which has become soft so as to stop any more damage being caused. What would be the best product to do this with bearing in mind the wood is/will be damp?
2. What should I put the glass back in with - linseed oil putty, mastic/silicone or the glazing tapes I have seen?
3. Once the glass has been refitted, what is the best way of sealing the exterior joint between the glass and the glazing rails - linseed oil putty or mastic/silicone sealant? Thanks for your help.

[Pete C]

Hi,

Best to treat the wood when dry, anything water soluble that can soak into the damp wood will most likely be able to leach out again, and could get onto the plants underneath.

Removing the glass and covering the roof with a tarp with plenty of ventilation at the sides would help the wood to dry out.

If the wood can be treated dry, Cuprinol Green can be used though it does stain the wood a bit. If this is a problem they also do a clear version.

If the wood really must be treated damp there is very little that will do it, try a search on octoborate/glycol preservatives.

Problem with linseed putty is the oil can soak into the wood and the putty dries out. Sometimes cedar greenhouses had no sealing round the glass as the panes overlap like tiles and leaks inside shouldn't be much of a problem.

If the greenhouse gets a lot of muck from overhanging trees then sealing between the glass and the rails with a UV resistant polyurethane could be the best way to go. Silicone may not adhere to damp wood so well.

To prevent new growth of moss and algae try fixing a strip of zinc along the apex of the roof, a goog on "moss zinc" will give some details.

If the rails are getting damage from the sun then some microporous wood stain like Sadoling will help protect them.

cheers, Pete.

[Bob Smith (UK)]

There is a liquid called "wood hardener" oddly enough. I think it was cuprinol, and found it at B&Q near the wood fillers. I used some a few years ago on a window ledge that had gone soft.

I removed the spongy wood first with a wire brush, then painted it on what was left before filling. It looks like water, but does make the wood go hard.

I don't have a tin to look at, and can't remember if it said it would work on wet wood, but like Pete C said, if the wood is dry, it will soak in and treat a greater depth of wood (I don't think you would want to remove your wood with a wire brush, since filler is probably not strong structurally)

Bob

[Chris Doran]

I have here a tin of Ronseal "Wet Rot Wood Hardner" which says the "wood should be reasonably dry...", so I assume it doesn't have to be completely so, This is just as well as I've left the windowsill painting a bit late and there's not much chance of nature drying out the soft bits completely. I'm trying a heat gun, but I doubt if it goes very deep.

Chris

[Pete C]

Might be good not to apply more than necessary if the wood hasn't been treated, as it could trap damp behind it and reduce it's ability to dry out.

If the wood hasn't been treated and stays damp it will keep rotting. But there are boron/borax etc products that can be injected/painted onto the damp wood to treat it:

Epoxy resin can also make a good wood hardener as it sets quickly.

cheers, Pete.

[robsut]

Thanks for the info, will have to see what the local sheds/building suppliers have.

Rob