Oak Fire Surround

[Paul555]

Not sure if anyone will actually stumble across this, but on the off chance they do..good day to you!
Basically, I could do with a bit of advice from people who's skill set is a bit better than mine when it comes to significant sized pieces of air dried oak. At the moment I'm trying to fit a new fire surround which will be rebated to overlap an existing marble back plate housing a gas fire. I have a fair experience of working with softwood and I understand the principles of cross-grain shrinkage etc, but not so much with oak.
1) When I was researching these bespoke cut or ready assembled surrounds, more than a few showed how they attached the cross piece to the legs and they were just using metal connection plates, screwed into a shallow rebate at the rear. Is that really the best way to do it, or just the easiest & cheapest for a quick fix?
2) The plastered wall to the sides and above the backplate is by no means flat. It looks ok to the the eye, but put a thick straight oak leg against it and the gaps show..maybe 3-4mm in places. I'm quite confident I can anchor the whole thing to the wall one way or another, but what to do about those gaps? Maybe a daft question, but would caulk suffice, or maybe another skim or two of plaster? Only ask because I've heard a few say to be careful, oak reacts with water, filler, plaster...blah blah.
3) Finally...the legs are 190mm wide, 90mm thick, and the mantle is 110 wide x 90mm thick, all European air dried oak. Should I be fixing the lot into place and waiting days, weeks or even months before it's stable enough to consider filling any gaps?

If you've got this far, thanks for reading. I don't want to sound like a complete novice but my experience is confined to softwood furniture. I can make Welsh dressers and huge 4 poster beds all day long...but as soon as you factor in buildings, bricks & plaster it's a different game.

If anyone is interested I will gladly post pics..

 

[Doug B]

Any chance of a link to the surrounds you’ve been looking at? A lot of fire surrounds are made from veneered MDF to help deal with movement issues of heat from appliances

 

[Paul555]

Thanks for the reply Doug. Those I've looked at have all been made from solid oak. I just get the impression that they're cut to length & width then banged together by a guy with a table saw who doesn't have a clue about movement & cross grain joints.

 

[Woody2Shoes]

Any solid timber will move. The extent to which your timber will move will partly be determined by which part if the tree each board has been cut from, and what other irregularites might be present from reaction wood, knots etc. There will be some movement due to 'acclimatising' to the new situation - next to a fire in a heated room - and some due to seasonal/weather variations, throughout the life of the piece.

Wherever plaster and timber meet, you need to allow for differential movement - one way would be to use a moulding or cover strip over the gap (fixed to wall or timber but not both). Another possible one would be to use a flexible caulk (probably paintable, like acrylic)

 

[TRITON]

Righty ok.
Not sure if this is exactly what you want but we need to make a start somewhere.

As luck would have it im doing myself a mantelpiece, and thats pretty much where you are .

When the 'thing' is screwed to the wall its not going anywhere, and theres no real forces acting on it, so simple joints should be fine.
Mine here is double biscuited(3 in 2 rows each side), but for your thicker section, something like loose tenon might be better. Anything should be fine, steel plates as youve said. Really only there to hold the mass of it together, shouldnt be anything structural about it.

Before we start though you should take note that air dried will want to move when the heat of a house is applied to it.Not sure if those thick sections will do much, but be aware they might want to twist, and likely to expand.

In my pics ive shown the outside edges that sit against my equally wobbly wall, and theres a bit of marble for it to go around, so to combat this i have those triangular sections sitting out as far as the marble sits off the wall and a bit more- to accommodate any scribing cuts.

Its triangular, as the thin section is considerably easier to plane when you scribe it to follow the undulations. Were it full thickness, it would be harder to plane, and you'll offer it us, scribe it with a pencil/block, and use a block plane or small plane to take off the high points. Triangular its really easy as its the thinnest section that rests on the wall.

So you could on each side add a piece like this, but as the top would then sit out, maybe leaving a gap, you could add another triangular piece to the top and scribe that too.
I'd suggest keep scribing and trimming till it sits flush on the wall, and as close to the marble is it ? of the fireplace. Any gaps, and you'd want it very close, you could use a dark silicon to fill it with.

What I intend to do there is use thin fillets placed on the edges to hide any gap, then any overhanging on the outside, ill mark and bandsaw them off, finishing with a plane so its flush with the front. Simply glued on, and maybe a couple of finishing nails, though maybe not, not really needed, the glue should be fine and even fitted i can get F clamps onto them

Again, just to get startedwith, so more questions are acceptable, but i hope you at least get the idea and we can move on or so from there

 

[johnnyb]

air dried was a poor choice here. I would want kiln dried plus tbh.

 

[Paul555]

Any solid timber will move. The extent to which your timber will move will partly be determined by which part if the tree each board has been cut from, and what other irregularites might be present from reaction wood, knots etc. There will be some movement due to 'acclimatising' to the new situation - next to a fire in a heated room - and some due to seasonal/weather variations, throughout the life of the piece.

Wherever plaster and timber meet, you need to allow for differential movement - one way would be to use a moulding or cover strip over the gap (fixed to wall or timber but not both). Another possible one would be to use a flexible caulk (probably paintable, like acrylic)

Thanks Woody...much appreciated.

 

[Paul555]

Any solid timber will move. The extent to which your timber will move will partly be determined by which part if the tree each board has been cut from, and what other irregularites might be present from reaction wood, knots etc. There will be some movement due to 'acclimatising' to the new situation - next to a fire in a heated room - and some due to seasonal/weather variations, throughout the life of the piece.

Wherever plaster and timber meet, you need to allow for differential movement - one way would be to use a moulding or cover strip over the gap (fixed to wall or timber but not both). Another possible one would be to use a flexible caulk (probably paintable, like acrylic)

Cheers, Woody. I'm expecting some movement, just not sure how much. The guys where I sourced the oak know their stuff and what I'm making with it, so I'm hoping for minimal shrinkage. One of them pointed out that the thick beams are prohibitively expensive to supply if kiln dried and assured me that the one's I've ordered should suffice.
I like the idea of the caulk..probably go that way unless they can also supply some thin moulding from the same oak.

 

[Paul555]

Righty ok.
Not sure if this is exactly what you want but we need to make a start somewhere.

As luck would have it im doing myself a mantelpiece, and thats pretty much where you are .

When the 'thing' is screwed to the wall its not going anywhere, and theres no real forces acting on it, so simple joints should be fine.
Mine here is double biscuited(3 in 2 rows each side), but for your thicker section, something like loose tenon might be better. Anything should be fine, steel plates as youve said. Really only there to hold the mass of it together, shouldnt be anything structural about it.

Before we start though you should take note that air dried will want to move when the heat of a house is applied to it.Not sure if those thick sections will do much, but be aware they might want to twist, and likely to expand.

In my pics ive shown the outside edges that sit against my equally wobbly wall, and theres a bit of marble for it to go around, so to combat this i have those triangular sections sitting out as far as the marble sits off the wall and a bit more- to accommodate any scribing cuts.

Its triangular, as the thin section is considerably easier to plane when you scribe it to follow the undulations. Were it full thickness, it would be harder to plane, and you'll offer it us, scribe it with a pencil/block, and use a block plane or small plane to take off the high points. Triangular its really easy as its the thinnest section that rests on the wall.

So you could on each side add a piece like this, but as the top would then sit out, maybe leaving a gap, you could add another triangular piece to the top and scribe that too.
I'd suggest keep scribing and trimming till it sits flush on the wall, and as close to the marble is it ? of the fireplace. Any gaps, and you'd want it very close, you could use a dark silicon to fill it with.

What I intend to do there is use thin fillets placed on the edges to hide any gap, then any overhanging on the outside, ill mark and bandsaw them off, finishing with a plane so its flush with the front. Simply glued on, and maybe a couple of finishing nails, though maybe not, not really needed, the glue should be fine and even fitted i can get F clamps onto them

Again, just to get startedwith, so more questions are acceptable, but i hope you at least get the idea and we can move on or so from there View attachment 101440View attachment 101441View attachment 101442

Thank you, Triton...that looks like a nice job there mate, but the legs on mine are 8" x 4", the mantle is 5" x 4" and the cross piece is 8" x 2"..all in solid oak, not box section. Appreciate the reply though, pleasure to hear from people who know what they're doing.

 

[Paul555]

air dried was a poor choice here. I would want kiln dried plus tbh.

Cheers Johnny, appreciate the reply but the company I'm dealing with explained that yes, they could supply kiln dried oak at the dimensions I need, but the cost would be huge and way out of my price range.

 

[TRITON]

Unless youre in a hurry, just keep the timber in the house. That way it will in a few weeks become acclimatized by the central heating.

My TV unit is in maple, and as the season changes wet to dry, it makes some terrific noises as the timber expands and contracts. Loud CRACK, thats the unit top doing its thing.

 

[Paul555]

Unless youre in a hurry, just keep the timber in the house. That way it will in a few weeks become acclimatized by the central heating.

My TV unit is in maple, and as the season changes wet to dry, it makes some terrific noises as the timber expands and contracts. Loud CRACK, thats the unit top doing its thing.

Thanks Triton. No, I'm in no hurry at all. Soon as this surround is fitted the wife's got plans to decorate the house so that'll be me up a ladder for a fortnight!

 

[Nelsun]

I've made a number of things out of "premium" "air dried" (Jewsons wording so pinches of salt at the ready) 8x4" oak sleepers with only minor movement. I did sift through their pile of split bananas to pick out the straightest they had the times I was in mind you. Splits haven't been a problem (butterfly splines have held well) and things have remained fairly straight with little twisting. Large floating tenons have worked well and pinning them with dowels or screws & plugs was probably overkill but made sure the tenons had a fighting chance.

The main things have been shrinkage and slight cupping and that's after c. 4 years.