FRENCH OAK

[epinay]

Well, maybe we did panic a bit, (thanks Andrew) but we will sleep well tonight and the next,  and the floor won't be as bouncy as it would have been with just one beam, and it will add character (which was sadly ripped out in previous renovation circa 1950), and we can have an open fire if we want, and I'm sure I can think of lots of other benefits to this more expensive 2 beam route we have hurriedly opted for in a state of nervous anxiety, just to reassure ourselves that it will all be worth it.  Like the floor may be able to take the weight of a bath now, which we had previously ruled out.  And we can have an open fire...... which is all we ever really wanted!

Thank you all.

Until our next conundrum....

Diana

 

[Poolguy]

Tony

Thanks for coming in on this one.

I am heartened that in your opening remark at least, you concur with the analysis and possible remedy.

 

But you go on to assign you professional empremarta to the previous course of action, which I find a little odd. I wonder had you considered that even though under normal operation the founding end of the beam may never reach flash point, it will be subjected to prolonged and rather intense heat. The inevitable result of this will be to ‘over cook’ the timber, which will cause tangential and radial checking and substantial shrinkage in that section. This would manifest as either case hardening or even ‘honey combing’ of the cell structure leaving it open to significant fungal attack duing the summer months.  I would go further to predict that under such an arrangement whether it was shielded or not the timber would suffer such degrade as to downgrade it structural and natural integrity perhaps 2 or more structural grades. Further I would expect significant distortion at the point where the over cooked timber meets the largely fresh timber. I am sure that this would have consequences for the bearing members and the floorboards above. Not a robust solution I would have thought.

 

In addition I am always looking for the possibilities in other than ‘normal operation’ of the fire/flue. Consider a chimney fire, where the flue and ensemble has not been cleaned for several winters and there resides a build up of soot. In the case where this ignites due to an overzealous fire being stoked, I have no doubt that the temps in the flue would reach melting point of the steel flue (I has seen this occur… very scary). This is ample I would believe to get the timber going as well and from there, even if you can put the fire out, the founding end of your beam is irrevocably damaged, perhaps burnt out. Your client would then be up for total replacement of the beam in a situation where the floor above hade to be removed and relayed. Very expensive.

 

You mention your ‘green lintle’ (do you mean Mantle) being 150 mm away from a log burner. I cannot see how this decorative piece of timber is in any way comparable to a major structural member. Just for the record, if you ‘lintle’ is crown cut then it will certainly ‘cup’ and if its box cut it will certainly crack longitudinally. But thankfully I expect that it may be easily replaced unlike Diana’s beam.

 

Moreover, the aesthetics of founding a large beam in what must be a beautiful old fire place would be quite disturbing to my eye… it would read as a ‘patchup job’ and not a ‘workmanlike solution’ .

 

However, to certify this solution with the empremata of the Institute of Structural Engineers (UK I guess), you are undoubtedly the expert in this matter, so I will remain as I am, I thought it might be worth raising those extra points of view nevertheless.

 

Andrew

[Caterham7]

Hendo.Just to clarify,My 'professional' recommendation would be to follow the course of action adopted,the later comments are my personal opinion which I would not necessarily certify.It's more a case of 'do as I say,not as I do !'.

Regards

[Caterham7]

I did spend half an hour doing a bit of research on the proximity of woodwork in chimneys last night as I thought there must be some relevant guidelines somewhere.The problem with current Standards and Regulations is that that they do not cover such massive chimneys.

In these cases it is often best referring to historic building construction publications.One such publication 'Building Construction-Advanced Course',Charles f Mitchell dated 1925 states - No woodwork should be built into walls or chimney breasts nearer than 12 inches from the inside of any flue.

So I suspect a beam with 16 inches distance would probably perform ok.

On the subject of so called 'experts' I do not feel that a typical chartered structural engineer can be considered an 'expert' since building construction and structural engineering is too broad a subject.'Experts' tend to specialise in one particular material or building type and it is the publications that these experts produce that general engineers refer too.I certainly do not consider myself an expert.

Regards Tony MIStructE (and proud of it !)

[Poolguy]

Tony

Thanks for your effort in following this one. It is interesting that there is a lack of regulation concerning proximity of timber to a heat source. The publication you mention seems to be dealing with this particular issue, and I wouldn't mind reading the background to their recommendation. Hence can you let me know the publisher so that I can get a copy. I'd like to know if their recommendation includes structural members or is limited to facia or framework.

As for your disclaimer, I don't think that you should be so harsh. After all no one expects any professional to have perfect knowledge covering all things, but as you have proven, you have access to research on the topic and you are trained to interpret and apply it. I think that principle applies to all professionals. Certainly my father is a member of the same august profession and will refer to his library in cases which are extraordinary.

I would add the we here have the obligation to direct those who seek advise to safe solutions rather than endorse solutions which might court disaster should the boundaries be approached too closely. I guess that I err on the conservative when dealing with building problems especially when its a DIY job or even a builder who is not supervised by a professional. Also we don't know who else after reading our recommendation might very well use that advise out of context.

Nevertheless, its good to debate these issues, I am sure that its a help to a great many people.

Andrew

[Caterham7]

Hendo,the publication I referred to gives no background to the recommendation.The tenth edition I have is dated 1925,published by B.T.Batsford Ltd,High Holburn,therefore I suspect finding a copy would be very difficult.

As far as current regulations go both the TRADA Timber Frame Construction Manual and Building Research Establishment Building Elements-Building Services state a minimum of 200mm between the flue and structural timbers.

Building Regulations and NHBC guidelines require a minimum 40mm air gap between the joists and chimney breast,since the joists then sit on the inner leaf of masonry which is immediately adjacent to the chimney,this distance can actually be less than 200mm

Therefore the conclusion probably is min 200mm for new build and say min 300mm for older buildings.

Regards Tony

[Poolguy]

Tony

Thats a good elaboration, interestingly those publication are looking at secondary member in one case, but I suppose we should assume that these are minimums in all case.

However, I was wondering if it only applies to a situation where the flue is installed in isolation where the is adequate airflow to disperse heat over the whole length.

In the case we are examining, the flue is contained with the exisiting chimney which is concentrating the heat into an updraft of heated air over the 2-3 meters till the ceiling height. As this heat cannot be dispersed I cannot see how the existing recommendations would apply. Hence the distance to the flue is largely irrelevant so long as the end of the beam is contained within the confines of the chimney we have a continuous super heated kiln operating on one end of this insitu structural member. hhhmmm.

Or am I over stressing the situation?

Andrew

[Bobdude]

Can I just 'borrow' this posting for a teensy weensy minute while all you Oak experts are assembled? We have some sections of large old oak beams which the builder cut out to fit a staircase. They are about 1 metre wide, and I have about 7 or 8 pieces. Would it be feasible do you think to get these sawed and planed to make treads for another staircase we wish to build? I thought they would look very nice. Thanks.

[Bobdude]

...........................and before my brain went off at a wide angle, I was thinking about the posting regarding temperatures necessary for oak beams to catch fire. We had a potentially devastating fire at our farmhouse, which thanks to the actions of the pompiers was brought under control before it was too late. My husband started it accidentally down in the cellar. The plumber was working down there and complaining about getting bitten by mosquitoes, so my husband had the brilliant idea of smoking them all out with some smouldering ashes he collected from the bonfire we had going outside. At some point the roof of the cellar (the floor of the ground floor) had been replaced by concrete beams, but the builders had not disposed of the old oak beams which had been stacked in a pile along one wall of the cellar, probably as they were too big to get out. The mosquito remedy worked quite well, but he must have dropped a few bits of ashes, and the next thing he knew the cellar was in flames! The fire was very fierce and he had to abandon it to the pompiers to sort out, but when it was put out, they showed him where it had started - the pile of old beams - and one had been burnt completely in half. They also told us that in a nearby village they had been fighting a chimney fire with 7 fire engines, working throughout the night, trying to save the house, but to no avail as it was completely burned out. My point being that it must be easier than we think for oak beams to ignite. (??) Not that I know anything much - I'm just a lady so don't all get on at me!

[zeb]

Sssssh lurcher......you'll start them off again!!!!

yawn.........

[Poolguy]

Hi Lurcher

Yes you can resaw your beams and use them as treads for the new staircase. I would say that they will look very handsome. However they will need to be dried carefully otherwise they will cup and distort, perhaps split. I would suggest you refer to someone with some experience in this.

You said that your beams were "one meter wide"

Do you mean 1 meter long?

I would scan them for metal first as most old beams have the od nail still in residence.

Sorry to hear of your fire. Must have given you a fright. Hope that the damage was not too extensive. What department are you in? If you don't find anyone local and you're not too far away I can help you with the resawing.

Andrew

(zeb .. what in heavens name is your problem???)

 

[Bobdude]

Yes Andrew, I suppose I did mean 1 metre long (but I was thinking of the width of tread on the staircase I suppose!) I'll bet that we are miles away from you - in the Indre 36 near Chateauroux. It might be difficult finding a saw yard who would do the job. But it would be nice to re-claim the original materials and re-use them in the house. By the way, the beams are about 6 inches by 8 inches - is that big enough for a stair tread? (Don't confuse me with widths and lengths again - I know what I mean! :whistling