Timber Frame, fill exterior gaps with...?

[Andys]

Hi All,

I have a timber-frame question.
One of our external corner-posts has evidently had some repair-pieces plugged into it and faired in with something like exterior polyfilla, mastic and a nice thick coating of bitumen to hide it all. Last winter turned the filler into a soggy mess so I've cleaned out the loosest bits to let it dry.

My question is: what now? I could fill it with mastic but thought a bit of lime mortar might be kinder - in the hope it might wick out any dampness ( unless of course it decides to work the other way and draw dampness in, which would be less good). To make it look good maybe I should mix the mortar with some carbon rather than blitzing it with bitumen to match the rest of the well-bitumen-ed timber frame.

Any thoughts?
Andy

With a bit of luck there might be photos...
https://www.dropbox.com/s/mb0a374scq18537/DSC02466.JPG
https://www.dropbox.com/s/5p6nz9rk8kloftv/DSC02467.JPG
https://www.dropbox.com/s/xhwxnr044nq33ym/DSC02468.JPG

 

[livias]

I am not an expert but I am little concerned that it is a structural timber and ought to be repaired properly. Though I could be panicking unnecessarily cos either

1. The frame is over engineered and the bits around the holes are plenty to support the house
or
2. The bricks are holding up the timbers

If that is so, then yes a lime mortar repair is a good idea and so is the plan to darken the lime mortar

 

[Andys]

Thanks Livias,
You have a good point and I've been keeping an eye out for movement for the four years we've been here.
I suspect the brick infill and the later addition of internal blockwork is holding it all together. The remaining timber does seem much tougher than I thought it would be, compared with poking some of the window frames...

 

[middi]

It does not appear that you have a structural problem - at present- , but your building may have in the future if the external timbers are unable to breathe. It has to be remembered that any externally exposed oak timbers will get wet and water will enter all " cracks and crannies" in the exposed timber, if this water is unable to evaporate or be removed from the penetrated timber or evaporated from it before it can be trapped within it then " rotting" process will start that will accelerate timber failure.
In an historic oak timber framed building, where some or all the external framework is exposed, the frame should be left bare to obtain that silvery grey finish which is commonly associated with the tannic acid in the oak having been leached out by rain and dried out by the wind in the frequent periodic cycle as common with our weather. Also, the masonary construction at either side of an exposed stud elevation should be of a permeable nature ( heavily lime based) as this type of construction will aid to " suck out" the water from the wet or damp timbers and disperse the content to the air therefore prolonging oak timber life. Small external cracks in external timbers are no cause for concern as any water will be quickly evaporated before it creares any permanent damage, if the cracks ( or cavities ) are quite large these can be filled with very porous lime render with and wool binder.
The process of how to look after external oak timbers on historic buildings has, unfortunately, been misinterpreted, and/or misunderstood, by many people leading to approaches such as painting, cement pointing, creosoting and other water penetration preventing measures such as mastics etc.
The ideal is not to stop water entering gaps or being absorbed ( as this is more or less impossible on a an historic external frame) but, ideally, for the penetrated rain or moisture to be removed as quickly and eficiently as possible by being dissipated back to the external element by wind, sun, breeze etc.
I hope the above will explain how to best treat your building exposed timbers.

MIddi

 

[Flyfisher]

The upper floor of the west-facing side of our timber-frame house has always been exposed (no sign of lath nails etc) and the oak frame has borne the brunt of over 400 summers and winters.

In contrast, the lower floor was rendered over, presumably with lime originally but with cement render since at least the 1930s and the sole plate was covered with modern concrete, also dating back (we believe) to the 1930s.

The upper exposed timbers are a bit gnarly but are rock hard. The lower 'protected' timbers have suffered some decay, especially the sole plate, which has had to be completely replaced in places.

Looking at andys' pictures, I suspect that the bitumen is doing more harm than good. As middi points out it's generally more important to enable wood to dry out than to try stopping it from getting wet.

As for filling holes, I'd rather do that with lime mortar than a modern mastic. It may be possible to blacken the mortar though anything that stopped it being permeable would obviously defeat the object. Might be worth talking to a specialist lime supplier about suitable dyes.

 

[Zebra]

Rather than find something to paint the repairs with to match the bitumened external frame, I think I'd be looking to remove the bitumen from the frame entirely. To my mind, those repairs do not present an eyesore. Whether they are good repairs or not I cannot tell, but if so, then they are a valid part of the house's history, and do not need to be concealed.

 

[Andys]

mmm, thanks for your replies everyone.
Having poked about a bit more, pulled off some pitch/bitumen, a few big chunks of mastic and damp filler, I think I might have a proper timber-framing-type carpenter round .
Any recommendations in Hants/Dorset/W.Sussex area anyone?

 

[Keithj]

Just back from a trip round Europe. Nice to be back.

I echo comments above. I spent a lot of money having concrete and mastic removed and rotten timber replaced. The timber that had been left to the open air is 500 years old and fine.

Have an old buildings expert surveyor look at the damage and advise. If the timber is sound and not in need of replacement, the advice will probably be (as above) to fill with lime. If you want the lime to be black, there are various options. On our plinth we used Beeck - a waterglass based treatment (not really a paint or a limewash). It's a bit fiddly to do but gives a true black result which matches the (unfortunately) black stained timbers.

I've not come across black limewash, but it may exist.