Cut through joist for flue?

[Maison_M]

Hello,

I'll try to keep it brief: we are having a wood stove installed, and the HETAS approved installer has cut through a joist in the first floor, and a joist in the roof to allow the flue to run up and through the roof (it has an angle in to avoid rafter).

There are now two joists (circa 200x40mm) which are only supported at one end, which is circa 3m from where they have been cut near the wall. The stove chaps are installing some timber blocking... but I always thought that double trimmers were required to take the load to the nearest joist either side?

I'd be really grateful for anyone's thoughts on this: is is standard/acceptable practice to cut through one joist with no issue? If so, can anyone point me in direction of regs/guidance for this?

Thanks so much

M

 

[bobasd]

why not post photos showing the cuts?
use the search button for "trimming" and look for joist trimming diagrams on google.

 

[Deleted member 174758]

The stove chaps are installing some timber blocking... but I always thought that double trimmers were required to take the load to the nearest joist either side?

Depending on the load, it generally is. I've lost count of the number of joist replacements/repairs I've done over the years where "other trades" had cut away or cut-out sections of "non safety critical" joists. I'd also suggest posting a couple of pics of their handywork

 

[Maison_M]

Thanks so much bobasd and JobAndKnock ... They are being pretty defensive about their work, and whilst I'm sure its fine in 99% of cases, it does feel like cowboy work as they just don't expect people to inspect what they are doing in floor voids! I dread to think how often this happens.
They are now packing out either side of the cut joist, but, as I have explained to them - this still doesn't pick up the load of the unsupported joist. Hopefully some photos are attached. In the roof there's one before I grumbled, one after I grumbled and timber packing got installed, and then one of the first floor void where there is no packing at all, but they've stuck a bit of fireline board on the end of the joist so it doesnt get too toasty. Great work.
Anyway - thank you for your comments, I just wanted to sanity check I'm not going mad, and that this is not good or even standard practice.
If anyone can point me in the direction of any regs/legislation on this, then that would be wonderful too.
Thanks
M

 

[lostinthelight]

Where is the flue supported/ suspended from . Out of interest Could you post a picture from below the ceiling of picture one , I cant figure out why there looks like self tappers into plasterboard

Flue looks like 5” flue?

 

[Deleted member 174758]

They are complete and utter cowboys. Adding in what they call packing isn't structural and makes little or no difference to the strength. Surely the gap around the flue should be sealed with some form of fireboard or collar? If they don't know how to do the carpentry work safely, they should employ a carpenter to do it for them. In fact are they actually HETAS certified, or are they just saying they are? Have you checked with HETAS? If they are legit I'd report them to HETAS for incompetence. I'd also have a word with Trading Standards. These guys are going to cause someone major problems sooner or later

 

[lostinthelight]

Floor joists and ceiling should be boxed and fittings used to hang the flue from and also isolate the flue so fire cant spread outwards. the fitting in the loft is to keep insulation away

 

[johnny2007]

Bodgers alert!
Maybe a stupid question, but couldn't they've checked where the joists were and position the flue in between them so not to cut anything?

 

[lostinthelight]

Bodgers alert!
Maybe a stupid question, but couldn't they've checked where the joists were and position the flue in between them so not to cut anything?

They should have checked but can take a long time to survey thoroughly.Its not always possible to get a run from stove to outside missing joists and rafters giving flue manufacturers clearance past them.
Its a bit easier if the stove position is flexible or offsets can be used that don't effect the flue efficiency too much and are aesthetically acceptable .

 

[Maison_M]

Thanks all once again. They are actually HETAS registered (I checked before I appointed them), and it never occurred to me to check that the installation quote (which is not cheap by any means!) included for proper carpentry work to support joist ends. It's like me checking that they've allowed to join together all the flue sections - it seems so ruddy obvious that it shouldn't warrant querying.
ANYWAY, they did come out to site to survey before putting together a quote, but don't recall whether they used a device to check where the joists were. The flue runs through two floors, and one pitched roof. There is about 1 to 100,000 chance that running a flue over that distance won't encounter a joist, so they really should have quoted on the basis that each floor it passes through will need trimming, or, angled flue sections required to step around joists. The only location a straight run was critical was ground floor, and we would have been perfectly happy to have a larger first floor flue boxing to step around the joist at ceiling level, but we were never asked. They did install an angled joint in the ceiling to step around rafter.
When I said I wanted trimmers at the end of joists, they said 'well that takes more time as we have to take the floorboards up, and you're going to have to speak to head office'... no shut it takes longer.
After bickering with the chaps on site, it was decided that they would complete stove installation so it is operational, and I will have to liaise with the main office to resolve the extra work for the joist ends. I guess my options are to either withhold final payment (70% of total) until it is addressed by them, or, pay them the outstanding, minus the amount I have to pay a carpenter to resolve.
It's so frustrating as they have been wonderful in every other aspect, and I don't want to make a small local firm suffer - but I have been left with a poor quality, and frankly, structurally negligent installation. Equally, I don't want someone else to go through this.
I have contacted HETAS, and they have sent me their complaint form - but they can't step in until I've exhausted resolution avenues with the stove installation company. I also don't know if the HETAS aspect will cover me for the structural works, as the stove installation itself appears to be fine.
Anyway, thank you all for your time. If any of you have any further guidance/input on this I'd be hugely grateful.

Thanks
M
ps - lost in the light - the screws are from the metal section frame around the flue on lower floor, which was then boxed out with fire board. The flue is a Schiedel twin wall flue, and at the point it goes through any floors/roof structure it is 180mm/7'' wide as insulated.

 

[lostinthelight]

Insulated flues are sized by the internal diameter if its 7” outside its 5” inside

 

[lostinthelight]

You may be able check some of their work by comparing to: https://www.schiedel.com/uk/schiedel-download/icid-installation-instructions/?wpdmdl=682

 

[Deleted member 174758]

...ANYWAY, they did come out to site to survey before putting together a quote, but don't recall whether they used a device to check where the joists were. The flue runs through two floors, and one pitched roof. There is about 1 to 100,000 chance that running a flue over that distance won't encounter a joist, so they really should have quoted on the basis that each floor it passes through will need trimming, or, angled flue sections required to step around joists.

When I said I wanted trimmers at the end of joists, they said 'well that takes more time as we have to take the floorboards up, and you're going to have to speak to head office'... no shut it takes longer

I wonder how they would feel if a structural engineer pulled them up on this (which I'm pretty sure they would)? At the end of the day if you are in trade and undertake to do a job, then you should be competent and the work should be both safe and competent.

The problem they faced isn't unique, and whilst I accept that stud finders are often inaccurate or untrustworthy, there are other solutions which are hardly new and which don't involve ripping up floors, etc (although they do require small holes to be drilled in either ceilings and/or floors). For example, several years back I was tasked with the problem of drilling holes through floors to allow for the installations of vertical soil stacks (pipes). This was in an old Victorian mill complex which the client was converting into "loft" apartments - 120 of them over 6 floors. For structural reasons we were not permitted to cut joists and trim out, and because of a screw-up the dry liners had already installed ceilings in about 1/3 of the units. My solution (which I had seen used on other builds by plumbers and joiners alike) was to use a laser plumb bob and drill holes through the floors to confirm where the joists were. Additional confirmation was done by inserting an inspection camera (endoscope) through each hole to confirm exactly where each joist on each floor actually was. Having sorted that out I was able to drill through the ceiling and mark a drilling point on the floor below so that I could repeat the process on the floor below. As this was over 10 years ago, and I had to hire the camera (I already had a laser plumb bob at the time), your HETAS guys really have no excuse for not doing the same sort of thing, especially as these cameras are now well under £300 a pop. Lack of investment is no excuse for poor, shoddy or dangerous workmanship IMHO

 

[foxhole]

When mine was installed any exposed pipe was heavily wrapped with chicken wire to avoid any risk of getting near it in loft space .
The run was carefully adjusted to avoid any need to cut timbers .