Any builders / engineers advice

[Ronin]

Victorian built house.

 

Fireplace in downstairs room.

 

Chimney breast continues into second and third floors..

 

Opening up the fireback to reveal builders opening,

 

Cut back plaster to locate lintel, which is 200mm wide, 250mm heigh and 1500mm length of stone with vertical crack at 1/3 in from one end. Essentially its in two pieces but shows no real movement

 

This is now propped.

 

Options -

 

1 - remove existing lintel and replace with steel or another masonary one - but weighing an estimated 300-400 lbs, this isnt viable..

 

2 - fit box section lintel or RSJ beneath existing lintel, supporting this by cutting into existing chimney breast at 150mm each side?

 

3 - build pillars on either side of existing chimney breast tie into existing brickwork and fit lintel within existing opening without disturbing damaged original stone?

 

 

Im fitting a multifuel stove and there is a huge amount of space so option 3 seems sensible to me, the base of the chimney breast extends down into the cellar and is stone built, so pretty substantial.

 

The cracked lintel has been in situ since the property was built and no movement is visible in the plaster above it.

 

 

 

Please discuss if you have any knowledge or experience of such things

 

 

[garyw]

option 2.less hassle. If theres no cracking to the existing plaster then its stable under load.

if you make lots of tea we can be round next week

[pe4king]

option 2.less hassle. If theres no cracking to the existing plaster then its stable under load.

if you make lots of tea we can be round next week

 

+ 1 on this option, prop/ support the existing lintel, ensure that each end of the new steel sits on a concrete pad stone, leave a gap of around 20mm between the steel and the existing lintel dry pack it with a strong sharp sand / cement mix 3 : 1 using cebex 100 additive once the dry pack has gone off 48 hrs remove the support and point in the gaps, jobs a goodun.

[VarmLR]

+1 to the above if the chimney space is large. I wouldn't advise it if the wood burner will be very close to the lintel. The only thing to watch with using steel lintels near woodburning stoves is that the heat can cause them to warp, which will crack the brickwork. I've seen this happen. The steel will also expand and contract and move albeit slightly.

 

You could go with option 3 but it wouldn't be as neat and (presumably) you'd have to use a full brick length/double width each side.

 

Some years ago, I had exactly the same issue with a similar chimney breast and fireplace, having opened it out to get to the original brickwork. I removed the existing lintel and replace it with a reinforced concrete lintel of similar dimensions. It wasn't a lot of extra work over the options tbh, so that's probably what I'd do if the problem came up again.

[brown dog]

Been around something similar myself. Much like Varm, my first reaction to steel girder or rsj options is: How hot will it get? But less about expansion etc, more about strength. If it's load bearing and going to get hotter than 300degC: http://www.mace.manchester.ac.uk/project/research/structures/strucfire/materialInFire/Steel/default.htm

 

As posted earlier, from what you've said, your brickwork must be stable. New reinforced concrete lintels would the way to go. You don't have to match the existing lintel cross section (which you can take out in manageable bits, rather than one (well, two!) massive pieces), put a couple of narrower ones in and brick the difference.

[simonl]

Don't forget that 'normal' lintels typically require a couple of courses of brick above them to become effective

[MJR]

Are you planning to leave the stone lintel exposed or plaster over it?

 

I don't understand the argument of RSJ versus concrete lintels as concrete lintels are reinforced with err steel......

[brown dog]

Composite steel beams (such as reinforced concrete) behave completely differently in fire to unprotected steel beams. Easy example: Twin Towers collapse. Or, (less risk of conspiracy theories!) collapse of steel frame hay barns in hay fires.

The rebar is, firstly, 'protected' by the concrete, and,secondly, it's primary role is to resist pull-force within a concrete beam that's trying to bend - it provides tensile strength to the concrete, that enables the concrete to better resist bending. Whereas a steel beam is trying to resist forces in all directions - which is why unprotected steel beams can go tits in fire when the tempersture robs them of their strength. Steel beam is not an optimal choice for use as a structural load bearer in a fire-hot flue!

From what Andy's described, I suspect the stress bearing in the brick above his litel is such that he could probably get it out un-propped with nothing more than a triangle of bricks above it coming loose -as the load must be being transfered away from the lintel, by the brickwork, at the mo (not saying that'd be a clever way to proceed!). Which means a steel-something solution could probably be 'got away with'; because the lintels only taking the weight of a small triangle of bricks above it. If the thing is actually to load bear, around fire temperatures: rft concrete lintels.

 

Time to hand in your wings?!? :)

[brown dog]

http://www.steelconstruction.info/Fire_and_steel_construction

[MJR]

Brilliant, love casting a fly......especially when I get a bite first time....

 

Anyone would think i know nothing of fire behavior.....

[geek]

For those who offer gratuitous professional services / advice, probably worth reading this legal case [2016] EWHC 40 TCC

 

Link to case here:

http://www.bailii.org/cgi-bin/format.cgi?doc=/ew/cases/EWHC/TCC/2016/40.html&query=([2016])+AND+(EWHC)+AND+(40)+AND+(TCC)

 

 

A guide / overview to the case here:

http://www.lexology.com/library/detail.aspx?g=8736fe9c-1aff-450e-b547-b8d859b5cc23

 

PS - I am an electrical engineer not a solicitor (but I am studying law), just thought it was interesting and relevant. I was asked a question at work last week about the risk of offering 'free' advice.

[Ronin]

Gents

 

 

wow thank you for your insights..

 

 

Ive discussed the requirements with a custom lintel manufacturer and have a suitable custom fabricated box beam coming later in the week.

 

The beam will provide support to the stone lintel - which I intend to leave exposed as a "feature" and covered (the steel) on the underside with suitable concrete backing board which will provide a measure of heat protection though this will be at 1.5 meters above hearth level, I doubt the stove will radiate sufficient heat to cause any structural weakness.