Preserving and treating timber shiplap cladding.

[mal62]

Any experts out there know of a good timber treatment/preserver suitable for shiplap cladding which i have just fitted to the outside of my chalet.I notice there are water based,oilbased,solvent based treatments available,i need to know which is most suitable for me.I believe the cladding is Western red cedar which has been pressure treated in the sawmill where i bought it,it does'nt look red in color though even though it's called that,it looks like ordinary sawn timber with a greenish hue due to the tanalising treatment.

 

[foxhole]

The pressure treatment will be more effective than anything you coat it with, some think that oil based coating can trap moisture but you can use any type, usually the more expensive types need less maintenance.

 

[JohnD]

you say you've already fitted it?

Best results are from treating it before fitting, then you can do the cut ends, top and bottom, and back, all of which are out of reach once fitted

The boards most prone to attack are the bottom ones, within 500mm of the ground, as they will get dampest. I would actually recommend you take these ones off and treat thoroughly.

Any ends that you have cut will need extra treatment

I recommend several flowing coats of Cuprinol Clear wood preserver, which is very good for preventing rot and worm.

Once it is fully dry, you can apply a water-based shed and fence treatment (not all are suitable for planed timber as it is less absorbent than sawn) which will leave a water-repellent waxy film on the timber, as well as a decorative stain in a colour of your choice. Once the boards have weathered for a few years and need re-treatment, the surface will have roughened so any fence stain will work.

The bottom boards, I recommend fixing with countersunk stainless steel or brass screws, as they are the ones you will have to re-treat, and eventually replace, first. You can cut and prepare a few spare boards for this purpose and tuck them away for the future. I actually put my spares between the battens, behind the cladding.

Give the bottom boards a slight kick-out so that water running down the face will drip away from the foot of the wall. Do not let the bottom of the boards touch whatever is underneath them (soil, paving, dwarf wall, whatever) as this will cause then to stay damp and decay fast.

I also use linseed oil as a treatment for outdoor timber, but it is much more work to apply and recoat (the waterbased fence stains are very easy, cheap and quick) and you have to treat the timber with Cuprinol or similar first, as you may get black fungus stains beneath the oil film. Other people seem to get this quite often. I only do it on hardwood which is expensive and intended to last a long time.

Here's one I did earlier:

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The strips covering the cut ends of the boards are actually dyed and oiled teak. Note that the bottom boards are kicked out beyond the dwarf wall.