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Oak Beams & Posts
Solid oak beams and posts in 100×100 mm, 150×150 mm and 200×200 mm sections. Oak is Durability Class 2, so it lasts outdoors without preservative, and its honey brown grain makes it the go-to timber for pergolas, porches, gate posts and feature beams indoors. Every size is stocked in our warehouse and delivered across Ireland.
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Oak Beams for Sale in Ireland
Our oak beams are solid square sections of oak, cut in three cross sections. The same sizes work as upright posts or as horizontal beams, so one page covers both. Every size is stocked in our warehouse and delivered across Ireland.
Oak Beam and Post Sizes
Choose the section by the load and the look you want, then the length on the product page by the span or the number of posts you can cut from it.
- The 100×100 mm (4×4 inch) section is the post size for pergolas, gate posts, fence posts, handrail posts and small porch supports.
- The 150×150 mm (6×6 inch) section is the all rounder, for porch and canopy posts, pergola beams, lintels and fireplace mantels.
- The 200×200 mm (8×8 inch) section is the heavy one for main beams, frames and feature beams that need to look substantial.
Take a shorter length for posts and short spans. Take a longer one when you need one continuous beam across a wide opening, or when you want to cut two posts from a single length. For any beam that carries a structural load, have an engineer confirm the section for your span.
Where Oak Beams and Posts Are Used
Oak goes where the timber is on show and needs to last, inside and out.
Outdoors
- Pergolas, gazebos and carports
- Porch and canopy posts
- Gate posts and feature fence posts
- Garden structures and raised bed frames
Indoors
- Fireplace mantels
- Exposed ceiling beams and lintels
- Stair newel posts and timber frame features
Why Choose Oak Timber
Oak is a dense hardwood that is hard to beat for posts and beams that stay outside.
- Durability Class 2: naturally resistant to rot, insects and fungal decay, with no preservative treatment needed to last.
- Heavy and strong: at around 720 kg/m³ it is stiff and strong for its size.
- Grain and colour: a warm honey brown with the character oak is known for, which is why it gets left exposed.
If your project needs a lighter, straighter softwood section, compare our Douglas Fir posts and beams. For oak boards and other species, see all our hardwood timber.
Setting Oak Posts Outdoors
Oak lasts longest when the bottom of the post can dry out between showers.
- Stand posts on a stainless steel post anchor or base, a few centimetres above the ground or concrete, rather than burying them.
- Seal any end grain you cut with oil so it takes up less water.
- Leave a small gap between the top of a post and any beam or roof sheet so rain can run off.
Fixings for Oak
Use stainless steel fixings only, A2 for most gardens and A4 near the coast. Oak is high in tannin, and tannin reacts with mild steel and galvanised fixings, leaving black streaks around every screw and bolt. You’ll find stainless screws, bolts and brackets in our outdoor timber hardware.
Will Oak Beams Change Colour?
Oak doesn’t need treating to last, but left bare it weathers to a soft silver grey within the first year. Most people oil it to keep the honey brown. Apply a hardwood oil in the first few months and refresh it every two or three years. See our wood oils and stains for the right finish.
In the first few rains, new oak releases tannin, which can mark light paving or render below it. Oiling the timber early helps, and so does protecting light surfaces while it settles.
How to Order
Open the size you need, choose the length and add it to your basket. Delivery is worked out in the cart. For every post and beam we stock, including other species, browse all timber posts and beams.
Frequently Asked Questions About Oak Beams & Posts
What sizes do oak beams come in?
100×100 mm (4×4), 150×150 mm (6×6) and 200×200 mm (8×8). Each comes in a choice of lengths, so pick one to suit the span or post height.
Are oak beams suitable outdoors?
Yes. European Oak is Durability Class 2 and naturally resistant to rot, insects and fungal decay, and at around 720 kg/m³ it is dense and strong. Stand posts on an anchor above ground rather than burying them.
What fixings should I use with oak beams?
Stainless steel only. Oak’s high tannin content stains mild steel and galvanised fixings with black streaks.
Will oak beams change colour?
Left bare, the honey brown weathers to a soft silver grey over about twelve months. To keep the warm tone, apply a hardwood oil for European hardwoods within the first few months and refresh it every two or three years.