Best approach for filling large gaps in old beams

[Leo]

Hi, first time poster and relative novice. Some expert advice or opinion would be much appreciated. We moved into a late 14th, early 15th farmhouse a few years ago and are now looking to do some restoration and redecorating. We have many wooden beams throughout the house with lots of big gaps. At some point in the past many of these gaps were filled in with something and then probably coloured to blend in with the oak beams. The same stuff has been used to fill in the gaps between beams and plaster on the walls. The filling looks like a sandy mix of something - maybe a lime mix? (please see attached photos). They are starting to crumble out now and many of them look unsightly. I am happy to open up the smaller holes but the bigger ones i think need to be filled in again. So I wonder if anyone could advise what they think has been used to fill in the gaps - it crumbles easily between the fingers. No doubt it is something very commonly used and completely obvious but as a novice on this stuff I am not really sure where to start! Following on from this any recommendations on what we should use and best approach to fill in large gaps? many thanks

 

[Cubist]

Hi Leo,
Shakes (cracks in the timbers) would typically be filled with a Burnt Sand mastic which is a blend of Boiled Linseed Oil and Burnt Sand. The latter is roasted by the producers to drive off excessive water which is necessary to secure a good bond between there sand and oil as it dries. Gaps between timbers can also be filled and sealed with the mastic but at the timber boundaries to plaster/render a suitable, usually lime based, filler is used as a final closing material over oakum and/or caulking cotton which is pressed into the seam.

Happy to provide more details if needed.

Cheers,
Cubist

 

[TudorCottage]

Hi Leo

Your internal beams look very much like ours in places.
I’ve taken a pragmatic approach indoors, as I feel whatever I do on the faces it will stick out like a saw thumb. So I’m leaving alone at the moment. That said, as Cubist mentioned I have put oakum and covered with a lime filler on gaps on the edges of the beams and I now have to look through the window rather than beside the frame for daylight

Outside I’ve been more proactive. Being exposed to the elements I felt I had to try and offer some TLC.
I’ve had a few beams professionally refaced and even refaced a couple myself. In other areas I’ve used burnt sand mastic, oakum and lime filler to try and offer protection against the elements. It became apparent early on that so many coatings had been put on the frame over the years that removing them 100% would have put too much stress on the wood (in my opinion) I used recommended ‘soft’ stripper and light abrasive techniques (is there such a thing?) and removed what I could. But I wasn’t pleased with the results, good in areas, patchy in others and awful in others.

Against many opinions on the forum I tidied up as much as I could and gave them a coating of Bedec Barn Paint. I’m very pleased with the results and I’ve stood in the pouring rain many a time and watched as the rain seems to roll nicely off the frame. According to the manufacture’s it’s all supposed to be breathable materials so I like to think I’ve given my oak frame a fighting chance whilst approving the appearance.

Only time will tell, but if it’s lasted 500 years with some of the gunk I got off it I’m hoping it will last a few hundred more.

 

[Zebra]

I've filled fairly large gaps with a mix of PVA and sawdust (the sawdust from a similar timber, of the same colour). It's not traditional, but it's hard-wearing and blends in well.

 

[Leo]

Hi Leo,
Shakes (cracks in the timbers) would typically be filled with a Burnt Sand mastic which is a blend of Boiled Linseed Oil and Burnt Sand. The latter is roasted by the producers to drive off excessive water which is necessary to secure a good bond between there sand and oil as it dries. Gaps between timbers can also be filled and sealed with the mastic but at the timber boundaries to plaster/render a suitable, usually lime based, filler is used as a final closing material over oakum and/or caulking cotton which is pressed into the seam.

Happy to provide more details if needed.

Cheers,
Cubist

Thank you very much for your reply and advice. I'll look into the burnt sand mastic and a lime based filler over oakum. Super helpful, thank you - Ill let you know how i get on.

 

[Leo]

Hi Leo

Your internal beams look very much like ours in places.
I’ve taken a pragmatic approach indoors, as I feel whatever I do on the faces it will stick out like a saw thumb. So I’m leaving alone at the moment. That said, as Cubist mentioned I have put oakum and covered with a lime filler on gaps on the edges of the beams and I now have to look through the window rather than beside the frame for daylight

Outside I’ve been more proactive. Being exposed to the elements I felt I had to try and offer some TLC.
I’ve had a few beams professionally refaced and even refaced a couple myself. In other areas I’ve used burnt sand mastic, oakum and lime filler to try and offer protection against the elements. It became apparent early on that so many coatings had been put on the frame over the years that removing them 100% would have put too much stress on the wood (in my opinion) I used recommended ‘soft’ stripper and light abrasive techniques (is there such a thing?) and removed what I could. But I wasn’t pleased with the results, good in areas, patchy in others and awful in others.

Against many opinions on the forum I tidied up as much as I could and gave them a coating of Bedec Barn Paint. I’m very pleased with the results and I’ve stood in the pouring rain many a time and watched as the rain seems to roll nicely off the frame. According to the manufacture’s it’s all supposed to be breathable materials so I like to think I’ve given my oak frame a fighting chance whilst approving the appearance.

Only time will tell, but if it’s lasted 500 years with some of the gunk I got off it I’m hoping it will last a few hundred more.

Thank you Tudor Cottage. I know what you mean - I also prefer my daylight via the window rather than the frame . We have the same issue and I think oakum with lime filler is a good way to go so I will try this. Some of our beams have actually had chunks cut out of them to accommodate wiring (done by previous owners) so these will probably require some replacement oak to be cut to size and slotted into the gap (carpenter to advise). Many thanks for your advice