Sealing gaps in old walls

[Mark and Jen]

Our new house is our first old one! There are various gaps here and there, which we would have previously just filled with some regular builders caulk. But I’m wondering if what worked on a new build might not be ideal on a house a few hundred years old! And in case anybody wonders why we are bothering with filling them at all-on our first night we had wasps get into the bedroom from a nest in the roof and they came in through exactly these sort of gaps! So it’s not just about keeping things neat ))

 

[Cubist]

Am I right in thinking these gaps are between sections of timber and perhaps plaster as well?

If so you could use a modern decorators caulking to close these but some of this stuff becomes too rigid and brittle and breaks up when the houses timbers move. Flexible silicone based caulks can perish over time and can, as they dry, lose their grip on one side or the other of a gap. The solution I've used extensively with this old place and often recommend to others is to use Caulking Cotton - as used by wooden boat builders - to fill first fill the gaps to a couple of mill below the final surface and finish this with a layer of fine finish filler. It will certainly help to keep out the wasps and other irritants.

(You can see an explanation of where to buy and how to use this in the thread 'Wooden Floor Sanding Project' which you can find with the Search function above)

 

[Mark and Jen]

Yes-that’s exactly what they are. Where the original timbers meet the finished walls. I’ll check out the thread you suggested!

 

[Cubist]

Would yours be a timber frame house by any chance?

 

[aockenden]

Yeah the caulking cotton is a solid option. Another option would be strips of raw sheepswool / fleece coated in clay and/or lime slip. When it’s moist it can be packed into gaps / cracks with a screwdriver or something like that, and then it hardens as it dries but remains somewhat flexible. It can be sealed over with clay or lime plaster and will hopefully remain flexible enough to avoid cracking.

 

[Mark and Jen]

Am I right in thinking these gaps are between sections of timber and perhaps plaster as well?

If so you could use a modern decorators caulking to close these but some of this stuff becomes too rigid and brittle and breaks up when the houses timbers move. Flexible silicone based caulks can perish over time and can, as they dry, lose their grip on one side or the other of a gap. The solution I've used extensively with this old place and often recommend to others is to use Caulking Cotton - as used by wooden boat builders - to fill first fill the gaps to a couple of mill below the final surface and finish this with a layer of fine finish filler. It will certainly help to keep out the wasps and other irritants.

(You can see an explanation of where to buy and how to use this in the thread 'Wooden Floor Sanding Project' which you can find with the Search function above)

So I read up on the cotton (and ordered some) but I’m not sure what I would do with cracks in beams once the cotton has packed out the hole. What can I put as a final finish that will blend with the existing wood (visually)

As a guide - I’m only worrrying about cracks I can fit a pencil in!

 

[Cubist]

Woah there. Yes, you could use caulking cotton to do this but I would be remiss if I didn't ask why you want to do it?

Such cracks in heavy timbers are called 'shakes' and unless they penetrate to the full depth of the timber they are usually left alone. Any effort to close these is typically associated with timbers that have an external face exposed to weather which allows rainwater penetration or draughts to the interior. The treatment for these includes the use of Oakum, Caulking Cotton, Burnt Sand and Lime Renders and Plasters. However, if you wish, I would be happy to explain how you might close and disguise such cracks to stope them becoming a residence for spiders and the like.

In your shoes I would not be concerned with the example shown in your photo and would focus for now on closing the small annoying gaps previously discussed. Besides myself there are other members here with some experience of the care and maintenance of timber frame homes such as yours and they too will be happy to help with any challenges you may face.

 

[jamest]

Absolutely with Cubist on the splits in your photo - these are a very common feature of oak produced when it dries (oak frames are typically constructed with green oak, which dries out in situ and cracks and splits along the grain). Personally, I would rather have more splits and shakes (inside the house anyway) than fewer as they add to the character of the beams. I've lived in a three old oak framed buildings and some of the splits were much bigger than yours and were never a problem structurally (that's pretty rare). Spiders sometimes set up home in them, but I don't really see that as a problem - they eat the moths and flies! Embrace the splits and shakes and admire their quirks, it would be a shame to fill them with anything

 

[Mark and Jen]

Woah there. Yes, you could use caulking cotton to do this but I would be remiss if I didn't ask why you want to do it?

Such cracks in heavy timbers are called 'shakes' and unless they penetrate to the full depth of the timber they are usually left alone. Any effort to close these is typically associated with timbers that have an external face exposed to weather which allows rainwater penetration or draughts to the interior. The treatment for these includes the use of Oakum, Caulking Cotton, Burnt Sand and Lime Renders and Plasters. However, if you wish, I would be happy to explain how you might close and disguise such cracks to stope them becoming a residence for spiders and the like.

In your shoes I would not be concerned with the example shown in your photo and would focus for now on closing the small annoying gaps previously discussed. Besides myself there are other members here with some experience of the care and maintenance of timber frame homes such as yours and they too will be happy to help with any challenges you may face.

Yes to closing then to spiders! At least the big ones …. How would I do that (the house has enough character without these )

 

[Cubist]

Ok, but you need to be aware that these timbers will move as they expand and contract. As a consequence any 'hard' fillers must be regarded as sacrificial because they will crack and probably fall out from time to time - regular repair may be needed.

First you will need a few basic tools and knowledge. The tools include a mallet, an old but blunt bolster chisel, a small 'stubby' flat bladed screwdriver and a sharp knife - an upholsterer's tack lifter is a very useful piece of kit too. Caulking cotton is supplied in various diameters, the most common of which is 8mm, but when it is twisted and pulled, as it must be during installation, this diameter can reduce to as little as 1-1.5mm. You will need to learn to braid multiple strands of the cotton to form ropes large enough to fill the target cracks and splits across their width. The cotton is then pushed or hammered gently but firmly into the split to fill it whilst perhaps leaving a bed, say 3-5mm deep, for a finishing filler. It is vital that the cotton has a firm grip on the sides of the opening and it must demonstrate some resistance to being pulled out.

As the cracks you are trying to fill will inevitably start at 'nothing' before widening to as much as 20mm before closing back to nothing over its length, you will find yourself starting with just one length of the cotton and tying on additional lengths as you progress toward the widest point - this is unavoidable and there will be a lot of trial and error involved.

Once the cotton is fully and firmly in place you have some options. You could leave the cotton exposed as it is or, as I have done at times, apply a little Milk Chocolate Brown emulsion paint to its exposed surface - this is a close colour match to old oak and can deceive the casual eye. Or you can apply somer fine filler over the rope and paint this with the emulsion.

All the materials are cheap and, barring the cotton, readily available so early mistakes will not be issue and can be easily rectified.

BTW - spiders are a good friend to timber frames as they prey on the beetles and flies that in turn bear wood munching larvae.

 

[Mark and Jen]

What sort of filler would I be using to apply on top of the cotton? Could I use a thin coating of regular flexible wood filler?

 

[Cubist]

You could but I would test how the filler takes colour before using it on the beams. sometimes you can get very odd results.

 

[Mark and Jen]

I have some dark brown flexible wood filler so I’ll try that in a hidden spot first!

 

[Kearn]

Yes to closing then to spiders! At least the big ones …. How would I do that (the house has enough character without these )

You just wouldn’t. Spiders are your friend in an old house, and will find somewhere to live regardless of our efforts.

 

[Cubist]

Yes to closing then to spiders! At least the big ones

The big, hairy, fast movers are garden spiders and seldom come indoors. Typically the ones found indoors have very small bodies and long legs and these will usually run away from humans. That said though, they can bite.

Seriously though these guys are friends. They make short work of more unpleasant visitors such as wood lice and will even attack larger beetles that may come in looking for accommodation for their off-spring larvae in your woodwork.

That aside, you'll never get rid of them - where there prey there will be predators and come what may you will be constantly brushing cobwebs away from every surface, nook and cranny.