Attaching heavy oak beam to chimney breast

Stainless threaded bar with a two part resin is a good method. Drill clearance holes into the back of the oak (do not go through the whole depth and blow out the face that will be seen) and same into the wall making sure they align with each other, it's beneficial to use oversized holes so you have wiggle room for positioning and to allow the resin some space to gain purchase onto the threaded bar. Will require temporary propping until resin has set. Setting times very depending on the brand of resin and conditions. JW Construction.

I did this once. Sledge hammered away a brick fire place and got 3 oak beams from reclaim yard. Sanded and cut angles by the edges of the seen parts. They were screwed in place with brackets 10mm were used cause I had these. Wall papered around the fire place. This smoked a bit then a copper hood was added this was lovely. The heat from the coal did mark the beam. But it was ok and the copper helped this. Oak beams will get hot and cracks in the wood will appear as it becomes drier. But it’s nice, it’s rustic. I also placed a slab of york stone in front. Very nice. The fact that it wasn’t just a beam and was resting on two vertical beams was a safer move. This was a country pub I did up in Kent.

Hi i did a similar project a while ago you obviously have to be precise with the holes if your not sure you could make a template from hardboard or thin plywood before you apply the resin

I agree with the previous answer to a point, but would be reluctant to chemfix the beam to the threaded bar, as this would be a once off deal and if you were to want to change this at a later date for what ever reason you have a lot of beating or cutting to do. So my advice would be to drill the corresponding holes in the Oak and then remove a notch in line with these holes and on the underside of the beam into which you could insert a washer and locking nut, once this is done, you fill in this notch with matching oak and all is hidden, so if and when you decide to change anything all that is required is to remove these plugs undo the locking nut and slide the beam off of the threaded bar. Good luck.