How to secure ‘floating’ mantle

[Seb101]

So I found this nice old piece of oak I want to use for a mantlepiece but because it wasn’t that deep I needed to mount it directly flat to the fireplace carcass to not lose any depth.

I have butted two pieces of 3x2 C16 to the back of it with 10 Big Ass Screws to a decent depth (see pics) to act as the mounting attachment. It’s pretty stable but there is the slightest wobble on it that I’m worried will get worse as the softwood timbers dry out more.

Does anyone have any clever ideas to strengthen this join? I thought maybe drilling some 10mm holes through the timber and into the mantle to 2/3 depth and hammering dowels in? Or even forcing an M10 bolts into the holes.

Ideas welcome!

 

[blup]

You could bolt through as you suggest.

Ideally you would want to support the load from underneath, because otherwise, however tightly you fix it, the load created by the beam will be transferred back to the supporting timbers, and there will be a risk of it moving away from them, in the way it is now through the "wobbling".

It is usual for the beam overlap the width of the fireplace but yours is actually narrower than the opening. Is that by virtue of design or necessity?

Cheers,

Blup

 

[Seb101]

You could bolt through as you suggest.

Ideally you would want to support the load from underneath, because otherwise, however tightly you fix it, the load created by the beam will be transferred back to the supporting timbers, and there will be a risk of it moving away from them, in the way it is now through the "wobbling".

It is usual for the beam overlap the width of the fireplace but yours is actually narrower than the opening. Is that by virtue of design or necessity?

Cheers,

Blup

The design is, as most things are now a days, on the whim of the girlfriend’s browsing of Pinterest. “Make it look like this” was the work instruction.

 

[bernardgreen]

Oak can corrode brass and steel screws, screws in oak should be stainless steel, bolts should be galvanised.

I would use wooden dowels 20 ~~ 30 mm diameter (red) glued into back of the oak (brown). Best if a wooden pin was used ( blue) in case the adhesive failed some time in the future. The dowels would then go into holes in the frame and be pinned with screws. (black)

 

[Seb101]

OK thanks, so I think doweling is the way to go. I assume the technique is to drill the hole the same diameter as the dowel and smash it in with a lump hammer?

 

[bernardgreen]

I assume the technique is to drill the hole the same diameter as the dowel and smash it in with a lump hammer?

No because that might cause the oak to split. Tight push fit and and glue

 

[Seb101]

No because that might cause the oak to split. Tight push fit and and glue

So do you drill the hole 1mm bigger than the dowel to account for the glue? Or drill the same diameter and sand the dowel until it's a good fit?

 

[bernardgreen]

Depends on what size dowel you have and what size drills you have. Sanding the dowel and then scoring it with grooves for the glue to run into would be the best option

I would clamp the backing timber to the oak and drill each hole through backing and into the oak. That will ensure the holes match and are in line.

 

[blup]

Pinterest! A triumph of design over practicality.

If you're going down the dowel route I would use a good quality auger bit and drill carefully to ensure nothing goes out of line.

I suspect it will require some judicious bashing.

Good luck.

Blup

 

[Nozzle]

I did something similar into a brick chimney breast, which was later plastered. Took quite a bit of measuring and a template to get right which you don't have to worry about. Drilled holes in the bricked, blow out the holes, use chemical fixing (Bloody brilliant stuff) and fix STAINLESS STEEL M8 threaded rods in the holes. Leave the rods too long.

With a drill and router, form holes at matching centres, but slightly oversized, then route or chisel a slot on the underside to allow enough access for washers, nuts, and fingers (giggiddy). allow for 15 degree of spanner movement to tighten the nuts.

Your situation is a little different as you can drill holes straight in the back of you prime timber, fix the STAINLESS studs tightly, perhaps boring a large enough hole to fit in and enire bolt head, then filling with some chemical fixant or two pack filler. Remember this is all from the back so you wont see it.. Make sure your studs are all parallel otherwise it'll be a pig to fit.

Drill corresponding holes in your chimney breast. Bolt. Job done.

Nozzle

 

[bernardgreen]

fix the STAINLESS studs tightly

Yes, stainless is better than galvanised.

 

[blup]

Drill bits, especially for a hole the length and diameter of which you have been recommended, won't drill concentrically so it is worth experimenting on some scrap wood first.

Blup

 

[foxhole]

I used 4 steel rigid straps , screwed to rear [full height of timber and recessed the steel into wall above the timber about 300 mm. ] secured and made good wall.

 

[Seb101]

Sorted. Thanks for the advice.