25 x 150 Shadow Gap Tanalised

Tanalised 25 x 150 Shiplap profile

Our exterior 25 x 150mm shiplap cladding is machined in the UK from quality Scandinavian redwood timber.  Shiplap remains a popular profile for many exterior buildings including garden sheds, playhouses, summerhouses, and workshops.  However, the ex-25mm is considerably more susbstanialand and lends itself to larger commercial blocks, offices and retail buildings.

We also maintain stocks of ex. 19mm x 125mm shiplap; ex.19mm x 150mm shiplap; and an ex. 25 x 150mm Shadowgap profile should these sizes be more suitable for our build. The Shadowgap is effectively a shiplap with a sleeker, more contemporary appearance.

Each profile has a timber lap which allows for some board movement which occurs when timber responds to different weather conditions. If wet timber dries quickly when the sun comes out it can reduce the lap considerably. After machining the boards are pressure treated with new generation Tanalith-E preservative.  This helps prevent rot and decay. Applying a waterproof timber treatment on the exterior will help maintain dimensional stability.

Shiplap and Timber sizes

Because our Shiplap has a planed finish it should really be described as ex. 25 x 150, but the actual size after machining would be approximately 20mm x 144mm. A further consideration is that approx. 10mm will be lost in the lap. So this tanalised shiplap finishes at 14mm thick and has a cover of 134mm, the technical drawing on this page explains much better than mere words. This profile can be used on a variety of buildings.  Board length availability can be variable; the normal range of pack sizes is 3.6 metres up to 5.1 metres.

Carcassing sizes will largely depend on what you are constructing, many sectional sheds use no more than a 25mm x 38mm batten. Spending a little more on “2 x 2” or “3 x 2” will not add massively to the cost. If you are cladding a building then we would recommend buying some pressure-treated corner profile, available in 2.4 metre lengths. Ideally all corner joints would have factory treated ends but this is rarely the case. To make the most of the timber you should apply end-grain preservative treatment. We sell Ronseal’s end grain preservative and they recommend two coats on any cross-cuts. You can then achieve a neater, and more weather proof, finish by using the Corner profile as well

Tanalith, Pressure Treatment, Tanalised and the Treated Right Warranty

The pressure treatment process helps to protect timber against decay and fungal attack. It also provides an improved service life to timbers that have only been dip-treated. All of our shiplap cladding timbers are pressure treated with Tanalith E preservative, i.e. they have been “tanalised”.  Our ex.19 x 150mm  redwood shiplap cladding carries the Manufacturers 15-Year Treated Right warranty. We recommend that all crosscuts should be protected with end-grain preservative treatment. Our preference is for Ronseal Decking End Grain Protector.

Oil based micro porous wood finishes

All our shiplap is pressure treated and will weather to a silvery-grey finish. Because the pressure treatment is water-based it is not waterproof.  Further protection should be applied depending on the product and it’s use. Shiplap used in the construction of a shed may be pressure treated but will need additional protection from moisture penetration. Apply a high-quality water-repellent paint or oil to help seal the shed, making sure that joints and fixings such as nails and screws, are well covered. A good microporous finish such as OSMO Country Colour or OSMO Natural Oil Woodstain both help control the movement of moisture through the timber surface