Best way to preserve timber?

[Nigel Watts]

I am currently repairing my shed/summerhouse and want to know how best to preserve parts of its timber base, which won't be visible and won't be easily accessible when my repairs are finished.

The shed - a bespoke design about 10 years old - was built on a set of treated deal joists. These joists extended beyond the footprint of the shed to provided support for treated pine decking. Much of the decking has since rotted, and have the ends of some of the joists. I have now sawn off all the joist ends and am rebuilding the decking as a separate unconnected structure in Iroko. One corner of the shed was resting on soil and the joists in contact with the soil have also rotted badly. I have now underpinned this corner by excavating soil and creating a concrete pad in its place. I have also reinforced the part-rotted joist with a piece of Teak.

The new decking will hide the cut joist ends and the part rotten joist but it will also make them difficult to access. Before completing the new work I would like to paint or otherwise treat the timbers. Should I use a timber preservative, bituminous paint or something else?

 

[Feltwell]

If you can Nigel, I'd soak them in preservative. I did this a few years ago in a similar situation - where getting back in to retreat the timbers would be very hard - I got some sections of plastic drainpipe, bunged up one end, dropped the timbers into them, stood them upright and poured some preservative into them and left it for a week to really soak thoroughly into the cut end. Seemed better to me than just brushing a bit on.

They were still OK when I moved out of the house a few years later, not sure what they're like now!

 

[middi]

the best way to preserve exterior timber, hidden from view, is with modern highly penetrating soluble complete wood treatment preservatives available from most builders merchants. ( cuprinol 5 star is as good as any). Make sure you flood the surface of the wood with a brush. Soluble preservatives are better than " solid" covers such as bitumen as these will stop the wood from breathing and if the outer covering of preservative cracks or is breached by moisture it will lead to premature rot especially in enclosed area with little air circulation.
Generally it has to be appreciated that whilst hardwood ( like Iroko) is water/rot resistant in it's own right it is not very absorbent as far as preservatives are concerned. The opposite is true with softwood .

Middi

 

[88v8]

Real creosote, available here
http://www.creosotesales.co.uk/products-page/

Beware! It's daaangerous :shock:

I would also cover any exposed end grain with lead, nailed on with silicone bronze gripfast nails.

Ivor

 

[jocelyn plummer]

Hey--WELCOME BACK MIDDI-------

 

[middi]

Hey--WELCOME BACK MIDDI-------

.
Ahhh......Thanks Jocelyn

Middi

 

[Penners]

I quite agree with the above comments about using a wood preservative. The important thing, as has been mentioned by Feltwell and Middi, is to get the timber as thoroughly soaked with it as you can. The end-grain in particular will continue to soak up liquid for a surprising amount of time, so it's worth repeating the end-grain treatment again and again.

I'm not so enthusiastic about capping cut ends with lead. This may prevent water ingress, but it also stifles breathability.

 

[davidbrac]

I did this 20 odd years ago, actually closer to 30 :shock: to soak into the end grain l put the solution in a bucket and soaked the ends for a few days, time consuming but well worth it.

Creosote would kill anything it comes into contact with and nothing will ever grow there again so if you use it don't get it where you don't want it. I would use one of the platinum chemical products cheaper than cuprinol et al in my opinion http://www.platinumchemicals.co.uk/timber-treatments-c-8.html?zenid=f41128d9e7bfaa54575fc4cbfbb0fd5b


We rebuilt a leanto shed construction last year, well Di did most of the work and l cut the planking from telegraph posts that were dumped behind the coach house when we bought the place. Easy when you have a sawmill but l stunk of creosote for days afterwards

 

[Nigel Watts]

Thank you for all the helpful ideas. I am now on a very tight schedule to get my garden ready for my NGS opening on 8th June, to which everyone is invited. Entrance is two pounds, which all goes to charity.

http://www.ngs.org.uk/gardens/find-...rch=type:advanced-pc:n7+8ls-d:1-dr:4&id=25137

 

[PeterI]

Thank you for all the helpful ideas. I am now on a very tight schedule to get my garden ready for my NGS opening on 8th June, to which everyone is invited. Entrance is two pounds, which all goes to charity.

http://www.ngs.org.uk/gardens/find-...rch=type:advanced-pc:n7+8ls-d:1-dr:4&id=25137

Going to try to get there this year (unlike last)

Peter