Beam repair

[Pennyviz]

Hi all

I have a beam that has rotted at both ends. Grade II listed house, CO has said would like to keep the beam, which was boxed in probably around 1860. The beam has dropped around 4 inches at one end to just mid way up the lintel and has a long bit of scarfing at the other end. Suggestion is to use a flitch plate and Z shaped cup at one end and longer cup on the other. Apparently I need to get a structural engineer to design these for CO and builder to be happy. Any body got any idea of cost or done a similar projec[attachment=0]beam5.jpg[/attachment]t?

Thanks
Penny

 

[GPHouse]

Ouch.

Is the building listed, assume so? From the photos it looks pretty knackered.... did you discuss replacing it with new, or a reclaimed timber of similar age/appearance?

Cant help on the cost much unfortunately - I had some work done by a structural engineer recently and it was £300 cash for a days work. Estimate closer to £500-600 for a day rate.

I replaced some purlins and timbers of a similar size with reclaimed old oak I found at a rec yard.

 

[GPHouse]

doh - grade 2.

 

[Pennyviz]

Yes although this way hopefully a 'repair' rather than alteration to structure, and preserves more of historic fabric etc.

 

[Flyfisher]

I had a very similar problem with bedroom beam that formed part of a roof A-frame. A roof dormer had been leaking for many years, possibly decades, and rainwater must have run down the rafter and into the joint with the roof plate. Because, like yours, the ceiling beam had been boxed in this water was trapped and thus created perfect conditions for rot. When I tackled the problem the ceiling beam was just 'hanging on' to the roof plate and I don't think it would have lasted many more years.

Here's the view from the bedroom (with the boxing removed from the beam):



And here the same area but from the scaffolding outside:



Because the ceiling beam was still in place (just!) it was decided to simply strengthen the joint with some steel straps - like this on the inside:


(Cont'd in next post)

 

[Flyfisher]

And like this on the outside:


And like this from inside the attic:



This repair was done in October 2008 and things haven't fallen apart yet! Hopefully it will see me out, though I guess that will depend on the quality of my welding! If I ignore my time then it only cost about £100 in materials, though it took me the best part of a week to do the whole job from start to finish. The biggest challenge was the fact that I couldn't (didn't want to!) weld the straps in situ because of the fire risk, so I have to measure carefully, cut and drill in the workshop, then bolt the pieces in place, quickly tack weld them (with many buckets of water at the ready!), then unbolt them, move back to the workshop and weld them fully, etc etc. I don't know how much it would have cost to have done commercially but I'd guess at least two or three days for two people.

All this was discussed with our CO prior to doing the work, though it was treated as a repair so LBC was not necessary. I didn't get a structural engineer or building control involved and simply 'guessed' that 10mm black iron would be strong enough to hold the joint in place. Our CO seemed happy with this and so far, so good! I'd say it's an 'honest repair' in that it is minimally invasive/destructive to the original fabric of the building and the metalwork is quite clearly a modern intervention (welded steel and stainless steel fixings).

I'm not entirely sure this is directly applicable to the question posed, but it shows that apparently major structural defects need not be hugely expensive to repair.

 

[Flyfisher]

Just one other point. We also had a large beam spanning a ground floor room that was embedded into a failing 'rubble' wall. When planning the repair of the wall (basically remove and rebuild) I was concerned that the end of the spanning beam might have decayed. In this case, I was using a specialist conservation building firm to do the repairs and they assured me that if the beam did need strengthening then a proven method would be to drill into the length of the beam (once it had been exposed) until solid wood was found, then use resin-fixed stainless steel rods to extend the length of the beam back to its original length to ensure a good bearing on the newly rebuilt wall. The advantage of this method is that such a repair would be completely invisible - and important consideration in this case as the beam is quite ornately carved and steel straps/plates would have been quite unsightly. Of course, this might not be such a consideration of the beam itself is to be boxed in.

Fortunately, such a repair turned out not to be necessary as the end of the beam was rock-solid when the wall was removed, but I mention it here as another possible repair method.

 

[malcolm]

You don't need a structural engineer or an architect! Your place was designed many hundreds of years ago and has proved itself by standing for all those centuries. If it has become a little rotten now any change will be improvement and will not challenge science, Structural engineers charge hundreds of pounds an hour and many are are complete numpties!

Here is a picture I didn't post before because of similar concerns about the 'rules'. I realise now that it is OK to post the photo to the world - we are the good guys and as nobody much bothers about the bad guys anyway we should be safe to talk about this stuff. For some DIY structural engineering steel is pretty strong. If you have it orientated horizontally it is a strap - migt allow some vertical movement. Orientate it vertically and it should add stiffness and reduce vertical movement. My photo is a wall tie with a clamp over the wall plate.

 

[Me!]

It's worth noting as well that a standard modern method of fixing the ends of beams in new-build housing is with a steel joist hanger, and that it really doesn't take very much steel to support even a large joist.
This one for example is for an 8"x8" beam.
I think that with the strength of even the solid bits of your beam being something that a structural engineer couldn't really calculate, I personally would go back to the CO and propose an "over engineered" solution using steel plates along the lines of the ones that Flyfisher has done.

Also, a question for Flyfisher please, how did you manage to drill your bolt holes so accurately through the beams that they line up with the steel plates on both sides?

 

[88v8]

OP, what's that beam supporting?

Ivor

 

[Flyfisher]

Also, a question for Flyfisher please, how did you manage to drill your bolt holes so accurately through the beams that they line up with the steel plates on both sides?

It was more a case of drilling the holes first and then fitting the steel plates to the holes. That's why the job took me so long. So, drill the holes in the beams first then mark up a steel plate. Drill that and bolt into place. Where the steel plates overlapped, 'tack-weld' them together and then carefully unbolt and remove the plates so they could then be properly welded on all sides away from the house to avoid the fire risk. This was done in a number of stages until the final result as shown in the photos. If you look carefully you'll see there are basically three finished sections of steel; inside the bedroom, the 'attic' piece and the outside roof plate. Yes, it was a bit fiddly and time-consuming (and moving the welder so often, especially up/down the scaffolding, was one of the biggest pains), but it wasn't particularly difficult in the sense of needing a high level of skill - just a methodical approach and patience. OK, the welding required a modicum of skill but I've found that a modern MIG welder and a little practice goes a long way. I only consider myself an 'agricultural' welder; I'm ok with large bits of metal but for anything with a degree of finesse - eg welding car bodywork for example - I'm fairly hopeless and end up with more holes than welds. Fortunately, for this sort of repair work 'agricultural' over-engineering is, I think, pretty much ideal.


Good point about joist hangers though. I've often thought they look somewhat flimsy considering an entire floor can be supported on just them and the nails that fix them, yet they are clearly strong enough. As malcolm points out, period properties have not survived several hundred years by being poorly built and, by modern standards, I reckon that the surviving ones are considerably over-engineered. That's not to say it was always the case, just that the poorly built ones have long since fallen down or been demolished.

 

[Pennyviz]

OP, what's that beam supporting?

Ivor

First floor bedroom floor Ivor.

Penny

 

[Pennyviz]

[/quote]

Good point about joist hangers though. I've often thought they look somewhat flimsy considering an entire floor can be supported on just them and the nails that fix them, yet they are clearly strong enough. As malcolm points out, period properties have not survived several hundred years by being poorly built and, by modern standards, I reckon that the surviving ones are considerably over-engineered. That's not to say it was always the case, just that the poorly built ones have long since fallen down or been demolished.
[/quote]

It was the boxing that put in about 1860 that has held in it in place since then! oh and probably a ton of dead woodlice. But that doesn't necessarily mean that I feel safe knowing the floor is held up by an inch thick plank and some dead insects.

Co has been very reasonable so far, so I am not sure how much more negotiation is possible.

Penny

 

[Flyfisher]

I certainly understand your feelings about wanting to strengthen things (I would too!), but if the boxing has held the beam in place for over 100 years then it's a good sign that collapse is not imminent, so perhaps you have time to investigate other options?

Our surveyor described in some detail the problem with the beam I described above and his report also recommended that, with immediate effect, I should cut a hole in the bedroom floor and lift some floorboards in the ground room floor beneath so that the beam could be propped from the subsoil, such was his concern about the state of the joint to the roof plate! When discussing things face to face he admitted this was overkill, but said he had to take the worst case view in the formal report. That is sometimes the 'problem' with professional advice. I didn't follow that advice and things remained stable for another year until I made the repairs described above. I suppose it's possible that, with the water ingress problem fixed, the whole joint may have lasted for decades without the steel straps. I'll never know, of course, but at least I no longer worry about it all falling apart - which is an important consideration in itself!

It sounds good that your CO is being reasonable, though that should not preclude you seeking advice from elsewhere. I don't know how much authority they have to insist on a repair being done in a particular manner, though I accept there's a fine line between 'repair' and 'alteration' and I certainly would not recommend a big falling out with your CO! Have you contacted any specialist conservation builders for their suggestions and perhaps a quotation? If you can find a good one (not always easy!) then they will likely have had plenty of experience with this sort of work and I feel sure there must be more than one way to make an acceptable repair at a sensible cost.

 

[Pennyviz]

I certainly understand your feelings about wanting to strengthen things (I would too!), but if the boxing has held the beam in place for over 100 years then it's a good sign that collapse is not imminent, so perhaps you have time to investigate other options?

Our surveyor described in some detail the problem with the beam I described above and his report also recommended that, with immediate effect, I should cut a hole in the bedroom floor and lift some floorboards in the ground room floor beneath so that the beam could be propped from the subsoil, such was his concern about the state of the joint to the roof plate! When discussing things face to face he admitted this was overkill, but said he had to take the worst case view in the formal report. That is sometimes the 'problem' with professional advice. I didn't follow that advice and things remained stable for another year until I made the repairs described above. I suppose it's possible that, with the water ingress problem fixed, the whole joint may have lasted for decades without the steel straps. I'll never know, of course, but at least I no longer worry about it all falling apart - which is an important consideration in itself!

It sounds good that your CO is being reasonable, though that should not preclude you seeking advice from elsewhere. I don't know how much authority they have to insist on a repair being done in a particular manner, though I accept there's a fine line between 'repair' and 'alteration' and I certainly would not recommend a big falling out with your CO! Have you contacted any specialist conservation builders for their suggestions and perhaps a quotation? If you can find a good one (not always easy!) then they will likely have had plenty of experience with this sort of work and I feel sure there must be more than one way to make an acceptable repair at a sensible cost.

Thanks FF yes beam has been 'uncovered' since May (and since supported by a fence post), various builders have been to look at it and then disappeared. CO suggested one conservation builder who wants to use Structural engineer/architect, which leads me here. It is a tricky one because of the length of scarfing on one end and that the other dropped end will probably have to be a 'Z' shape to avoid raising the dropped ceiling up.

Penny

 

[Flyfisher]

I know it's frustrating when builders come to look and then never return but it's probably for the best if they feel the job is too much for them or they don't know how to tackle it, but it's such a shame so few can even bother with a telephone call to say they're not interested. Oh well.

It sounds as if you're doing all the right things though - these sorts of problems all have their unique details and challenges and the important thing to remember is that pretty much anything can be repaired in one way or another. I take your point about the complications of raising the beam back to its original level - we have many unlevel floors upstairs for similar reasons of historical movement, but that's just something to live with rather than try to correct, IMO anyway.

Just one other thought, have the reasons for the original beam damage been addressed? In our case it was clearly due to a long standing roof failure so was fairly easy to fix.

Good luck with it all - let us know how things progress.

 

[88v8]

OK, so it's not supporting anything much. That makes it much easier. We have a rotted off beam end that I've propped up with one end of a door frame, and that's how it will stay, that too is supporting nothing much.

Here
http://www.idostuff.co.uk/sections/DIY/Joist_End_Repair/Joist_end_repair_1.html
are some basic illustrations.

Not as easy with an older house, but basically the scarfed end looks OK as a starting point unless it has rotted again or worm has been in it, and the other end will need a piece added to it so it can be fastened back to the wall.
Obviously some minimal destruction will be needed to expose the stone/brickwork around the ends, and at the right-hand end - in the pics - some floorboards will have to come up and the ceiling will have so undergo some careful impairment, so that the rotted end can be sawn off.

Exactly how it's sawn off will depend on how it's going to be repaired, but minimally all that is needed is to remedy the visuals with a piece of wood that extends an inch into the wall. The actual work of supporting it will be done by an iron thing that can be made by your local blacksmith. Keep it simple, although its position over a window opening is unhelpful and I presume it must in part be resting on the lintel beam.
You'll need to do some chiselling here to expose the junction and this will in part dictate the design of the support.

I presume that wall is stone, what about the other end?

Ivor

 

[JanJonWestWales]

Why not do a scarf joint and post&brace to reinforce???

This is what we have done to two rotten-ended beams
https://4.bp.blogspot.com/-Mm72_M4CnTA/UsrUWqdXkvI/AAAAAAAAABc/P68K5284PKA/s1600/IMG_1829sml.jpg

 

[88v8]

Post my previous questions, I think you will find that you/we can remedy this yourself, quite easily. I have a cunning plan.
I await your advices, as they said in the olde days.

Ivor

 

[CliffordPope]

If the CO is so keen to preserve the actual beam, as an artefact, rather than simply an appropriate replacement beam, then what about cutting off one end back to sound timber, shifting it along into the wall at that end, and then doing a proper spliced timber replacement extension at the other end?
Neater and sounder to repair one end only, rather than both?