Treating crumbling old oak beams

[surreysteve]

We are renovating a 15c Medieval cottage and slowly removing the "involuntary vandalism" perpetrated in the 1960s. There is a lot of work but we enjoy it and we are in this for the long haul!

The house is chock full of old oak beams that were painted and also filled during the 60s. NB In the main the beams are rock solid however the filler was largely used to cover a few beams that had wood worm infestation and perhaps other rot in them.

We have spent around 6 months cleaning the paint of the beams with chemicals and even more laboriously picking out the dreaded filler. Having done this amount of work to clean them we intend coating with nothing more than a clear bees wax/turpentine.

I am not worried about the woodworm returning nor other beetle attacks as the beams are 500 years old and probably pretty unappetising now. However, several beams are crumbly and soft and I was looking for a treatment which would strengthen the wood and prevent further crumbling. NB I have already given them a fairly good wire brushing. The affected beams would now be best described as intact - but aerated and soft....a bit like balsa wood!

I have seen a wood hardening treatment from Ronseal and also a more specialised strengthening treatment Bencon 20 but would welcome any advice on what we should do.

Thanks

Steve T

 

[worms]

Steve, just bouncing this one back to the top, since I know it is a topic that plenty of folk on here will be able to advise on. It unusual for a new member to arrive with 15th C beams and not be welcomed with open arms, but they are pretty tied up at the moment talking about the effect of tv licenses on global warming, and Penners has a wedding to organise!

 

[skier-hughes]

A few pictures would help giving us an idea of how much wood is left etc.

 

[surreysteve]

Thanks for this....I think I am slowly working out how to do attachments

Hopefully some pictures attached to this post!

Steve

 

[Bayliss]

As a newbi to the forum and still learning about the art of conservation I am no expert in offering advise. However for the benefit of debate I would suggest that the beams that you speak of are not the main structural timbers? If they are you will need to consider splicing in new sections of timber, the hardener, in my opinion will not be suited to add structural strength. If the timbers are ceiling beams/wall studs then the odd few here or there present no real hazard and may respond to hardener, although again I would certainly prefer to replace the timber or if possible splice in new.

 

[Flyfisher]

Do you have any idea of the extent of the crumbling compared with the dimensions of the beams? A penknife blade, small nail or similar pressed into the beam might give you an idea. Basically you need to know whether the beams is rotten through or just the outer few cms.

I'm no expert but I've always understood those wood hardener solutions to be mostly applicable for stabilising localised areas of rot/decay prior to filling and painting - for which I assume they are fine (having never tried them) but, like Bayliss, I don't think they can replace structural strength.

 

[Keithj]

I've just been through the baptism of fire on this. About 40% of our wall timbers were seriously rotten, and had to be replaced - mostly the sole plates (all gone, because of the concrete a clever builder smothered over them years ago).

We found that the timbers that were open to the air may be a bit crumbly for the first few mm, but were like iron thereafter. The restorer who did most of the work used a sharp screwdriver to diagnose - it either went in a couple of mm and stopped, or went all the way in. Where the timber had "gone", being structural, there was nothing to do but replace it.

We had a firm of consultants look at the timbers when we started. Their view was that two-pack filler may have solved some of the problems 15 years ago when the rot was only localised, but not any more.

Where we had superficial crumbly oak, a wirebrush removed the grotty bit and left a reasonably "authentic" surface.

 

[Penners]

Welcome surreysteve.

I endorse what has been said above about the crumbly bits of your beams. If the infestation attack is really serious and has reduced the great majority of the beams to Malteser-filling, then you may have to consider repairing them with new oak, to restore their structural strength.

But if (as is, in my experience, more likely) the crumbly bits are a minority area of otherwise big, strong, beams, then you really have nothing to worry about, except the aesthetics of the situation.

In this latter case, you have a choice of approaches. You could use a draw-knife to shave away the crumbly bits - but this is a pity if they can be visually rescued.

If they're not excessively crumbly, you may find that a simple treatment with beeswax might restore sufficient stability for them to look fine and stay intact (albeit weak). Melt the beeswax and brush it well into the affected wood.

If the affected areas are literally falling apart to the touch, then Bencon 20 may be the answer. My daughter is about to use that product on some old oak window members that almost turn to dust if you blow on them (the window is being retained purely as a decorative feature, rather than a working window). Unfortunately I can't give a report on its efficacy because she's not doing the treatment for a week or two yet.

 

[surreysteve]

Many thanks for comments so far.

I have tried to post some pictures and think i got it right second attempt - although they have yet to appear!

If they don't appear by tomorrow I will re-post!

Steve

 

[tobydog]

Rick Lewis from Traditional Oak Carpentry came round to my house a few weeks back. He was looking primarily at the sole plate but had a very good look at the rest of the house. I have two studs that are in very poor condition but, as referred to earlier in the thread, they are two of several and therefore I won't be replacing them anytime soon. I'll just stabilise them.

What actually surprised me was how much elm I have in the frame. On moving in I had assumed it was all oak. Most of the elm is very sound and hard, however, I now understand that it doesn't have the same solid heart wood in the same way oak does. So a dodgy looking oak beam or stud could be perfectly good just underneath the surface, howefer, dodgy looking elm may not be so good. The two studs I mentioned are elm and I can poke a sharp point straight through them in several places. Just personal experience.

 

[surreysteve]

Pictures have now appeared so hopefully that is helpful.

To answer the point, 95% of the beams are really solid and the ones that have a problem are just soft/aerated on the outside. So this is not really a structural issue, more a preservation and aesthetics issue.

I hope that helps and thanks for advice so far.

Steve

 

[Penners]

It's interesting to see from your bottom picture that someone has, at some recent point, inserted an extra joist next to an old one. Presumably this was because the old joist was badly deteriorated (although in the picture it looks pretty sound). It's also interesting to see evidence in that picture that the house might once have been a jettied building, which was later added to.

The top pictures shows pretty typical woodboring activity on the surface of the beam. Have you dug a penknife in to see how deep this goes?

The middle picture shows some fairly bad deterioration around a mortice. That mortice will in itself have weakened the joist somewhat. It's difficult to see all of the joist in the picture, at that point, but I suspect it might benefit from some reinforcement - perhaps by inserting a companion joist alongside it (as in your last picture).

 

[surreysteve]

Tried the 'penknife' test....goes in about 1/2" then rest of beam is solid.

I'm surmising from all this that my best course of action is to just give a coat with beeswax and have some extra characterful beams! They have been there 500 years so guess they should see me out anyhow.

NB No-one has mentioned the Ronseal wood hardener treatment (apologies if this was an idiotic idea!) - I have seen that people have used this on infested oak furniture with good results.

 

[skier-hughes]

The pen knife test is god, leave them be. You don't need any treatments if they are this good, assuming that the toal width of the beam in question isn't down to one inch )

 

[Penners]

It sounds as though you don't have any structural worries at all. Ronseal wood hardener seems to do what it's designed to do, but do you really need it? If you just want to prevent dust and make the beams look nicer, the beeswax treatment should do the job for you.

 

[geoff]

From the pics your beams look very like mine did (oak 200yrs +) - crumbly and powdery on the surface but like cast iron in the heartwood underneath. Luckily, I had some spare bits (where lintels needed replacing etc) to experiment with first. One problem was the colour where the crumbly/powdery bits were - it was a sort of orangey brown which was not that attractive; your pics seem to show a similar colour on a couple. I tried wire brushing but it was a little bit hit and miss - if just very wormy it was not too bad as there was still a bit of structure, but where it had gone very powdery it just came off in clouds of dust (wear mask!) and looked a bit stark and skeletal - a bit like a large dog had gnawed it!. I tried various hardeners, but the results were not always very good. The best was a furniture restorers' hardening fluid - I can't remember the name right now (brown tin, black illustration) but it's in the shed and it's 11pm so I will look tomorrow sometime and can post it if you want to try it.

It can work ok, especially if it's not too powdery, BUT it alters the look of the wood as it can dry with a slight sheen and it darkens the wood and makes it look like it's been varnished - basically hardeners are simply liquid resins in a hydrocarbon solvent. The fluid can be very sticky and the powder and bits can stick to it when you apply it. If you want natural pale finish I don't think it will be much use because of the way it looks afterwards - and you would have to coat the whole beam or it would look horribly patchy. Clear waxing after hardener doesn't hide that, I found.

My beams had originally been fumed to a dark finish, and had been waxed afterwards. In Wales the dark finish seems to be traditional, and I was happy with that. I found after lots of trials on the spare bits that the best result was with ordinary wax - just Liberon Dark Oak liberally applied (two coats) and gently rubbed in and buffed to just a slight sheen. It seems to stabilise the damage as well as it dries a bit. It also filled many of the worm holes and looks pretty good. I did use hardener on a couple of bits and the dark wax blended it in quite well, but I didn't bother much with it in the end - the wax on it's own seemed better in my opinion. If you don't like a dark finish and want a clear 'natural' finish I think you will have problems if your beams have a lot of worm and powdery decay - but just clear wax on it's own is probably your best bet. I also found the liquid wax was not as good - for floors and smooth surfaces it probably saves time, but for irregular, wormy damaged beams it was just a messy pain in the a***.

 

[andrew gayton]

Avoid excessive defrassing of timbers and walk away from the tin of ronseal etc etc . Remember that not all framing members were intended to be visible; certainly in the eastern region, the vast majority of framing was concealed behind daub/plaster/limewash - it is only post build ill advised 'restorations' that have seen previously covered elements visible. In the situations where frame members were exposed, they were limewashed. The widespread stripping back and adoption of the black and white approach started in the 19th c and gathered pace during the early part of the 20th c flirtation with mocktudorbethan.

 

[fluffytail10]

Sorry to raise an old thread, but as is my want I have been poking around while my Boyf was out of town. anyway this is the story.....

When we bought our house the couple told us an old beam in the study has been boxed in and replaced with an RSJ. However, chatting with the neighbour she gave us a different story. She had uncovered the other end of the beam in her house - it was riddled with beetle and had told the neighbours. They basically told her they were selling the house and there would be trouble if she mentioned it to anyone. So i went a poked a hole in the boxing and discovered there was in fact a beam and not a RSJ.

Well anyway the beam is riddled with huge holes - much bigger than woodworm - about 2/3 mm across, and is basically crumbling away. As this is all that is holding up the second floor i am kind of worried. Yes I have poked it with a penknife and there seems to be no solid bits as far as i can see.


Should I be worried? what should I do next? Cant send pics as quota has been reached :|

fluff

 

[JoceAndChris]

Good grief, how completely irresponsible. There must be sound structure there or you would have known about it, but it needs uncovering, all rot cutting out, and new wood or other strong material putting in. Good luck - pics would help!

 

[FamilyWiggs]

It needs proper investigation and if necessary repair/replacement.

However, it is very unlikely to be as bad as you fear (it is possible/probable that the heartwood is as strong as steel still) and if it isn't, I doubt it will fail in the next few days.

Await BF's return and discuss next steps together. Removing the boxing would seem to be one of them.

You can see what can be done - even when the end of a beam has failed totally, on this thread:

http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=13058&hilit=oak+scarf