Log Burner on Floating Wood Floor

[sandman1600]

We’re installing a log burner in our lounge. The floor is a floating wood floor with a 60cm gap underneath and a solid concrete foundation.

We know the log burner needs a solid base so we were originally told that we’d need a solid concrete base from the foundation to floor level to take the weight of the log burner (105 kg) plus a tall (3.65m wall) chimney breast.

We’ve now had someone else quote for installing this and they’re adamant that we don’t need a solid concrete base and that a base made out of blocks and concrete lintels would be sufficient.

I just wondered if this sounded reasonable?

 

[lostinthelight]

Look at the installation instruction for your stove which should tell you what thickness hearth you can use. A lot of stoves that don't get above 100°C underneath can be placed on a non combustable hearth of around 20mm thickness straight on top of the wood floor.If its a free standing stove the hearth should be a min of 840 x 840mm in size as long as its 150mm larger each side of the stove and 225 mm in front of the stove if it isn't designed to run with the doors open
You cant count the weight of the flue as it should be fully supported from above with no weight on the stove itself as that should be removable without disturbing the flue

 

[sandman1600]

Look at the installation instruction for your stove which should tell you what thickness hearth you can use. A lot of stoves that don't get above 100°C underneath can be placed on a non combustable hearth of around 20mm thickness straight on top of the wood floor.If its a free standing stove the hearth should be a min of 840 x 840mm in size as long as its 150mm larger each side of the stove and 225 mm in front of the stove if it isn't designed to run with the doors open
You cant count the weight of the flue as it should be fully supported from above with no weight on the stove itself as that should be removable without disturbing the flue

Thanks for the reply.

We’re okay with the thickness of the hearth and we’ve got that sorted. It’s the “strength” of the floor beneath the stove and the hearth.

As I said, it’s a floating wood floor so we need something UNDER the floor to support the weight of the stove (and the hearth).

 

[lostinthelight]

Whats the makeup of the floor, there must be support joists resting on the concrete surely.

 

[sandman1600]

Whats the makeup of the floor, there must be support joists resting on the concrete surely.

There are joists but there’s a big drop beneath the floor. Everyone we’ve spoken to has advised that we need a solid support as the floor/joists aren’t sufficient to hold the weight.

We’re just trying to establish the best way of achieving the support.

 

[jj4091]

Personally I would think the guy saying he/you needing a solid concrete base cast under and around the joists is ensuring there is absolutely no chance of any subsidence, whereas building block pillars with lintels across them supporting the joists leaves a risk of the pillars sinking into the sub-base. However if you have a newish house with 4 inches of over-site concrete on which to build the pillars there should not be a problem with that method.

 

[lostinthelight]

If you know the joist sizes and span it could be worked out I guess ..Furniture/ sideboards full of crockery etc, can weight as much as a stove mind

 

[sandman1600]

If you know the joist sizes and span it could be worked out I guess ..Furniture/ sideboards full of crockery etc, can weight as much as a stove mind

Like I said it’s over 100 kilograms concentrated in quite a small footprint with a tall stack of bricks and timber above it.

 

[foxhole]

Have my stove on a suspended timber floor , not a problem ,no additional support required. A lot of people weigh more than your stove ( me included)they don’t fall thru your floor?

 

[sandman1600]

Personally I would think the guy saying he/you needing a solid concrete base cast under and around the joists is ensuring there is absolutely no chance of any subsidence, whereas building block pillars with lintels across them supporting the joists leaves a risk of the pillars sinking into the sub-base. However if you have a newish house with 4 inches of over-site concrete on which to build the pillars there should not be a problem with that method.

Okay that’s makes sense. Thanks very much. It’s a 1970s house and the concrete foundations seem really solid and no signs of subsidence so I’m guessing the solid concrete base might be overkill.

Thanks again. That’s really helpful.

 

[sandman1600]

Have my stove on a suspended timber floor , not a problem ,no additional support required. A lot of people weigh more than your stove ( me included)they don’t fall thru your floor?

Yeah that’s a good point too. I haven’t fallen through yet!

There is some “spring” to a floating floor though so I guess the tall chimney breast above does need some stability.

If it was a standalone stove without the chimney breast I’d be a bit less concerned.

 

[lostinthelight]

Yeah that’s a good point too. I haven’t fallen through yet!

There is some “spring” to a floating floor though so I guess the tall chimney breast above does need some stability.

If it was a standalone stove without the chimney breast I’d be a bit less concerned.

So is the stove not freestanding but within an existing fireplace? if so different rules apply .

 

[sandman1600]

So is the stove not freestanding but within an existing fireplace where different rules apply?

There’s nothing there currently and we’re building a tall chimney breast to house it.

 

[lostinthelight]

I see using insulated twin wall flue then and the structure needs to be of totally fireproof materials including framework and no pink plasterboard cladding within the opening even if clad in slips or the like

 

[sandman1600]

I see using insulated twin wall flue then and the structure needs to be of totally fireproof materials including framework and no pink plasterboard cladding within the opening even if clad in slips or the like

Yeah that’s all been taken into consideration. It was just the base/support I was questioning. Thanks.