Douglas Fir Tongue and Groove Cladding
Douglas Fir tongue and groove cladding is available in the following profiles:
- IWC1 - 19mm x 145mm overall, with a 135mm face - For horizontal or vertical fitting
- IWC2 - 19mm x 95mm overall, with an 88mm face - For horizontal or vertical fitting
- IWC3 - 19mm x 142mm overall, with a 125mm face - For horizontal or vertical fitting
- IWC4 - 19mm x 145mm overall, with a 125mm face - For horizontal or vertical fitting
- IWC5 - 19mm x 145mm overall, with a 125mm face - For vertical fitting only
Most of these profiles are flexible enough to fitted either vertically or horizontally barring IWC5, which is only suitable for vertical fitting. If you want to fix your cladding with "secret nailing", then you can select our IWC3 profile.
If none of our standard profiles meet your requirements, please feel free to send through a drawing of the profile you need, and we will be happy to get a price for you.
The 18/15 Clears grade Douglas Fir we supply is a light reddish-brown and has very few knots. This modern, uniform look is very popular and with the help of some great machining this traditional material can be pulled into the future.
In order to preserve your cladding as long as possible it is highly recommended that you treat the boards. This will protect them against moisture movement and make sure that you don’t get any visible gaps due to shrinking and expanding with the seasons. For best results treatment is best applied before your Douglas Fir tongue and groove cladding is fixed.
The machined boards we supply in our Douglas Fir tongue and groove cladding are 3m and longer. These lengths are supplied randomly however if you want certain lengths please call us on 01889 279 018 or jump on the chat and we’ll be happy to see if we can get the lengths you need.
If your lengths are available, please enter them in the “Special Instructions” box on the checkout page and we’ll process your order accordingly.
Be sure to read through our treatment information by clicking on "Treatment Guidance" above. It talks about sealing, preserving and protecting the timber from the sun's UV rays. Here are quick links to the products we recommend:
These fitting guidelines are only a rough idea on how to fix your tongue and groove cladding. We do recommend you employ a professional who has experience fitting tongue and groove cladding.
Be sure to read our treatment guidance as treatment needs to be applied prior to fixing your cladding
Consult a fitter to determine if your scenario would require the fitting of a breathable membrane between your wall and the cladding. This membrane stops rain getting to the wall, but allows moisture to escape, helping to prevent internal condensation and mould that can come with it.
Treated Softwood Battens
Treated softwood battens (available from our cladding accessories pages) are most commonly used to fix to the wall (or on top of the breathable membrane) to then fix your cladding to. If you are fixing your cladding horizontally, your battens need to be placed vertically, at around every 600mm (60cm), and vice versa.
** Whether you use nails or screws, it's important that they are stainless steel, or silicone bronze ARS, so that the natural tanins in the timber will not corrode them. Never use iron nails for fixing timber.
To help stop the wood from splitting we recommend pre-drilling the timber and then holding it with the screw head when you fit the board to the batten. Look to leave a 3mm gap between the boards to account for any moisture movement and make sure that the tongue is facing upwards otherwise moisture will start gathering in the groove of the profile.
You can also use nails, preferably ring-shanked for extra grip, and again stainless steel so they don't corrode. For lower-density species like cedar, consider using nails with larger heads so the cladding doesn't pull through.
You can fit IWC 1,2,3 and 4 vertically or horizontally depending on the look you want from your timber. Whilst technically you can fit IWC5 horizontally, water can sit in the square channel, which is not recommended.
With each new row of cladding you add, it's preferred that you stagger the joins between each board so you don't create a visible seam.
As already stated, these are just ideas to get you thinking about installation and you should consult a professional installer before fitting your cladding as every scenario is different.
Treating Timber Cladding
All of our timber cladding is provided untreated.
For best results, cladding should be treated before it is installed to ensure application of the treatment on all sides and ends of the boards.
We recommend Wood Finishes Direct for all of your treatments. We have found them to be well priced and their telephone support and advice is second to none. We highly recommend giving them a call.
The following information is from Wood Finishes Direct in relation to treating timber cladding.
When it comes to treating your timber cladding, there are three areas of protection to consider.
- Sealing against moisture movement - Sealants are used to help prevent moisture entering the wood causing it to expand. Kiln dried timber like European Oak will definitely need to be sealed, and for other timbers it is highly recommended.
- Wood Preserver - Helps to prevent rot and protects the wood from insect infestation and mould.
- UV Protection - The ultraviolet rays of the sun slowly bleach external timbers. UV protection oil helps to keep the natural colour of your timber for longer and prevent it from turning silvery grey so quickly. Some people like their timber to weather and prefer the silvery grey look so it’s completely down to you.
The following links will take you straight to the products on Wood Finishes Direct's website:
Product to Seal and Preserve
To address Sealing and Preserving, they recommend applying one or two coats of "Wood Preserver Basecoat - Barrettine Premier Universal Preserver" before installation to seal against moisture movement and protect it from mould and insects.
Product to Protect from UV Rays
Then to optionally delay weathering, two coats of OSMO UV Protection Oil. There are different colours of OSMO UV Protection Oil available, with names like 'Cedar' and 'Oak', but these colours are to make other timber look like the stated species. We recommend the 420 clear version which interferes the least with the natural colour of your timber.
What do our customers say?
The quality of the kiln dried oak you sent looks really good & some of the best I have seen in my 9 years of being self employed, so thank you very much for that
Very detailed website for ordering my exact requirements easily.
- Richard Boundy
Just a quick line to say thanks for the swift delivery of the ash I ordered a couple of weeks ago. It is now installed as stair treads/ landing and looks superb. Just one small gripe, the delivery driver didn't call me to say he was on his way which meant I had to rush over; he did help me carry it into the house though.
I think the picture does them justice.
- Stephen Barker, Spalding
You were recommended by my builder
- Catherine Hilditch
I felt the ordering process was very straightforward, your pricing very good and response when requesting a sample was very prompt
- Steven Boyd
Architect / Design Specify
85/15 Clears Douglas Fir External Cladding Tongue and Groove Cladding from iWood Timber
Some commonly asked questions
How long does the cladding take to deliver?
Because we are sourcing our wood based on demand to ensure the highest quality, delivery may take from 14 to 17 working days once your order has been placed with us.
What are your delivery costs?
We calculate our delivery costs based on how far away you are from us, to get more information on this please check out our shipping costs page HERE.
Aside from delivery locations that are priced on application, your delivery will be provided with means of offloading from the truck. This may be by HIAB (lorry with a crane arm), or by supplied manpower. The method will be determined by the haulage company we use based on your location and available options at the time. Please note, both offload options will drop your order to the side of the lorry, they won't be able to carry it around the back of a property, for example.
For areas that are priced on application, by default, we will quote for delivery on a flat-bed lorry that you'll need to arrange to offload yourself. We can quote for offloading on request, but to these areas it's usually prohibitively expensive, and cheaper for you to hire a forklift, or arrange to have enough people on-site to offload.
How do I place an order for cladding?
You can place your order online by working out your price above and adding your items to your shopping basket. You can then check out and your order will be processed securely and a confirmation email sent. Once your order arrives in our depot, we'll give you a call to arrange delivery.
Can I Order Samples?
Yes you can, you can order samples of certain timbers at www.iwood.co.uk/sample-request/.
If the species you need isn't there please give us a call or talk to us on our online chat.
The timbers shown are planed all round samples and are not profiled.