February 16, 20242 yr We have recently moved to rural Aberdeenshire, Scotland. Our property has two steadings and a bothy. You can see the dilapidated end of one of the steadings in the photo. We call this one Mordor as it is the steading from hell which we can't use for fear of death from falling masonry; it's a project for another day and another bank account! Please see attached photos. The bothy is the issue for today. The pointing is in a terrible state: a mixture of very eroded hundred-year-old lime mortar and newer sand and cement repairs. The advice from a local roofer/mason is to rake it all out and replace it with lime mortar. The mason's estimate for the work was way beyond my budget, but he guaranteed it for a hundred years!!! I haven't done work like this before but the resources are all there on the internet, so I'll do it this year. What I'd like advice on, please, is how to repair the chimney stack. Let's assume that I might use it as a chimney sometime in the future. Crows have nested in the chimney stack and in the end wall of the bothy. They cleverly removed mortar to create access. You can see right through the chimney stack in one of the photos. There are quite large voids to be filled before the outer faces can be pointed. The stack has weathered three severe wind storms in the last twelve months but it won't last forever in its present state. The mason recommended that I collect stones to fill these voids but I don't know how to do the repair with these stones. If I place stones inside the voids, do I just cover them in mortar to secure them and restore the inside shape of the chimney, then build the chimney back out of the hole? How do I finish the outer faces? Please help!! Many thanks for any contributions.
February 16, 20242 yr Get a wire brush and screwdriver and rake out some of the old mortar at ground level. Then a bucket of lime mortar, a small trowel and some gloves and have a go at repointing yourself. It's not rocket science. By the time you get to the chimney you'll be plenty proficient to make a tidy job of it.
February 16, 20242 yr The good thing about lime is it goes off very slowly so big batches can be made without fear of “going off”.
February 17, 20242 yr Also when pointing stone I like to wait till it’s fairly stiff (which might take a few days) then wipe with a soft paint brush to give a better finish.
February 17, 20242 yr Author Thank you for all the very useful advice ... Now, do I need to buy a small cement mixer for a job like this or can I easily make multiple mixes by hand/shovel? If I'm doing this job on and off, over weeks, how helpful will a small mixer be?
February 17, 20242 yr 2 minutes ago, Tapster said: can I easily make multiple mixes by hand/shovel? Yes. Pointing doesn't take large quantities so I'd do it by hand, otherwise you may spend more time moving the mixer and cleaning it than actually mixing anything.
February 17, 20242 yr Author Thank you, Mike .... secondhand mixers seem to be around 200 quid in these parts; that's a bit much for me. Lime mortar seems quite forgiving, so mixes will last a few days, meaning I can mix more each time and not have it go hard. Yay! ............. and, er, incomplete/ incompetent mixing doesn't matter too much?? Edited February 17, 20242 yr by Tapster
February 17, 20242 yr A mixing paddle for a drill would speed things up for mixing up a bucket or two.
February 17, 20242 yr 1 hour ago, Tapster said: mixes will last a few days No. The lime for granite is the hardest grade, and it doesn't keep overnight. Your local BM should know the grade for your sandstone if it is a local product. However, I read that unless there is a quarry nearby, it is as likely to have come in by ship.
February 18, 20242 yr 22 hours ago, saveasteading said: No. The lime for granite is the hardest grade, and it doesn't keep overnight. Do you mean that granite should use nhl5? I can’t see why 3.5 wouldn’t be fine and that certainly will knock up next day in this weather
February 18, 20242 yr 5 hours ago, jfb said: granite should use nhl5? mortar should also be as strong and durable as possible (while still softer than the masonry). So I'd make local enquiry.
February 20, 20242 yr Author On 18/02/2024 at 17:58, jfb said: On 17/02/2024 at 19:05, saveasteading said: No. The lime for granite is the hardest grade, and it doesn't keep overnight. Do you mean that granite should use nhl5? I can’t see why 3.5 wouldn’t be fine and that certainly will knock up next day in this weather Mine's softish sandstone, so I'll be looking for a softer mortar by the sound of it. Any suggestions?
February 20, 20242 yr Just googled this…..Type N Mortar Mix It is considered to be a general-purpose mix, useful for above grade, exterior, and interior load-bearing installations. It is also the preferred mortar mix for soft stone masonry (such as limestone). Type N is the mortar most often used by homeowners and is the best choice for general application.
February 23, 20242 yr I’d use 3.5 nhl with sharp sand mixed at ratio 1:3. dont make it too wet. Push it into the joints and don’t worry about leaving excess around the joint. Next day (or when it has dried a bit) compact with tool/bit of wood and clear off any excess. Then use a churn brush (or softer) to do a final brush over.
February 29, 20242 yr https://www.scotlime.org May be of use & they run courses in the skills you wish to learn.
March 7, 20242 yr Author 5 hours ago, Hughgo12 said: Few snips from drawings - standard regurgitated spec but can be useful Great, thank you! The precise technique details are particularly helpful. 😄
March 7, 20242 yr That's interesting to read. The addition of stones to large gaps makes sense, as does max 10mm if thy are hard stone. Wouldn't it be best to use a piece of stone recovered from the building, ie the same strength? or to make up some aggregate from recovered stone?
March 7, 20242 yr 1 hour ago, saveasteading said: That's interesting to read. The addition of stones to large gaps makes sense, as does max 10mm if thy are hard stone. Wouldn't it be best to use a piece of stone recovered from the building, ie the same strength? or to make up some aggregate from recovered stone? Originally it probably would have been whatever was dug up locally. Lime mortar is supposed to be sacrificial and compressible strength properties are not that important, unlike cement mortar which is desired for its compressible strength and hard wearing ability.
March 7, 20242 yr 1 hour ago, Hughgo12 said: Lime mortar is supposed to be sacrificial and compressible That's why I thought that using the same sandstone it could also crush or crack rather than stress the main masonry blocks.
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