MMeNDtal Posted March 7, 2020 Share Posted March 7, 2020 Hi all! Joined a while ago, but finally ready to start putting stuff back together after ripping it out! This is my first time renovating a property, so I'm getting help and advice locally, but I have some more specific questions I'd like to ask on here. The property is 150+ years old, rubble stone construction, rendered with cement. The next job is to construct stud walls and insulate the upstairs. Could someone possibly point me towards the best forum to ask about this topic? I'm particularly concerned about managing damp. Thanks! Link to comment Share on other sites More sharing options...
Thedreamer Posted March 7, 2020 Share Posted March 7, 2020 I am sure others will be long shortly but first point is it definitely a cement render on the stone wall (with no cavity this means that moisture won't be able to pass through). I lived five years in a old house on Skye and it was nightmare to heat and had damp issues. Is the plan to build a timber stud house within the house? Whereabouts are you? Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 7, 2020 Author Share Posted March 7, 2020 Hi and thanks for the reply! We're in Shetland. Are you saying the interior face of the stone wall should have a cement render? The (very) rough plan I had in my head was to stud frame the interior walls, leaving a void space for the stone wall to 'breathe'. These walls wouldn't be structural. Link to comment Share on other sites More sharing options...
Thedreamer Posted March 7, 2020 Share Posted March 7, 2020 You might be the most Northerly member! The outside wall, I would imagine that loads of houses around you will have had cement render (this was probably applied at a later date, originally the outside wall might of been just stone or prehaps a lime render). I have a cement render on our new self build but it's on block with a cavity between that and timber frame kit which means that the cavity acts as a break. When you start mixing up modern materials and old materials you can have problem with moisture/dampness. This becomes more of an issue as you become more thermally efficient and airtight. There are ways around this, just requires some thought. This forum is a great place to ask questions as some on here are pros and others like me just are learning as we go. If it was me I would consider the condition of the metal roof, sarking and also I would want to know about the ground floor (rough concrete slab or suspended timber floor) That internal stone work looks amazing. Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 7, 2020 Author Share Posted March 7, 2020 Yes, I love the look of the stone and would re-point it and leave it exposed in some areas, but the wife isn't so keen! We've already had to do some repairs to the roof and plan to rip off the profile sheets, and replace any bad boards, then re-cover with tiles, when the weather permits! Link to comment Share on other sites More sharing options...
ProDave Posted March 7, 2020 Share Posted March 7, 2020 Hi and welcome. We already have another member from Shetland @Hobbiniho I wonder which of you is the most northerly? That looks a nice house, in generally sound condition. I have worked on plenty of these, which were the "standard" house construction for a long time up here. Most renovations of these are as you suggest, an internal timber frame with insulation not touching the outside walls. The problem with this is you create a "tent" inside the house and the void between the frame and the stone is cold because it must be ventilated. Most people fail miserably on the detail, e,g remove a switch or a socket and you are greeted by a howling cold gale blowing in. If I was doing this, I would make the insulated timber frame, and then seal the inside with air tightness membrane taped and sealed, and then create a small service void inside that for wiring and plumbing without letting the cold air in. The performance of the house will be down to how thick you make the frame and how much insulation you fit. Sadly most builders seem to think 25mm of kingspan is okay and 50mm is fantastic. I would be aiming for a very minimum of 100mm if not more. The other thing I would do in the part of the roof that forms the sloping coombs, is I would sister some more timber onto the rafters so you can get a decent level of insulation in there while still maintaining a ventilation gap between the insulation and the sarking board. That looks a very small stair opening, it must have had a near vertical ladder originally? Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 7, 2020 Author Share Posted March 7, 2020 (edited) Thanks for the reply! We're hoping to turn the stairs 90 degrees, to open up the downstairs space. I'm trying to visualize what you're describing, regarding the stud wall. Is this about right? Edited March 7, 2020 by MMeNDtal Link to comment Share on other sites More sharing options...
Simplysimon Posted March 7, 2020 Share Posted March 7, 2020 hi, i'd be looking to insulate to the outside to mitigate the damp issues and minimise the reduction in floorspace Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 7, 2020 Author Share Posted March 7, 2020 I've not really looked into insulating the outside, but, if I were to do this, would the inside require no insulation or just less insulation? Is there anything else to consider when insulating the exterior? Link to comment Share on other sites More sharing options...
Patrick Posted March 7, 2020 Share Posted March 7, 2020 @MMeNDtal Welcome. That looks great. Nice project. 1 Link to comment Share on other sites More sharing options...
ProDave Posted March 7, 2020 Share Posted March 7, 2020 1 hour ago, MMeNDtal said: Thanks for the reply! We're hoping to turn the stairs 90 degrees, to open up the downstairs space. I'm trying to visualize what you're describing, regarding the stud wall. Is this about right? Not quite. Outside to in: Stone wall gap 100mm (or more) frame filled with insulation air tight membrane taped at all joints 25mm battens following frame studs to create a service void for cables etc Plasterboard. That will give you an air tight structure I doubt insulating outside will stop all the damp, this house will have no foundations as such and no damp proof course. 1 Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 7, 2020 Author Share Posted March 7, 2020 Yes, that's right... No DPC. So, there wouldn't be a requirement for a vapor barrier between the stone wall and 100mm frame? Theoretically, what happens to any moisture in the stone wall? Thanks for everyone's help, so far! Link to comment Share on other sites More sharing options...
Cpd Posted March 7, 2020 Share Posted March 7, 2020 I have renovated something very similar, and built a timber frame within the stone walls and insulated both between the studs and over the top, it’s an ongoing project....... My outside walls are cement pointed and painted multiple times and will continue to get painted, they are approximately 700mm thick with rubble in the centre. The way I got ventilation was to create some holes very low down on the outside into the rubble centre and are covered by a stone details (a mini roof) to prevent water ingress, the inside walls of the house have also been pointed but again there are various holes for ventilation. The final part was leaving the top of the walls with some ventilation to the roof. I have a 50mm gap under the sarking boards and above the start of the roof insulation for ventilation and then a vented ridge. This whole elaborate set up means that all my walls and roof are ventilated, air can get in low down from the outside and make its way all the way to the ridge. I live on the west coast of Scotland right by the sea and it’s very windy so this pretty much guarantees good air circulation. I am confident that this will deal with any damp ingress from the outside and now I can concentrate on the stud work, insulation and detailed vcl. I am doing the work myself so am able to take my time and really get the detailing correct. You do loose a lot of internal space this way but for me I wanted to keep the rugged exterior stone work as a feature and therefore did not consider external wall insulation but in your situation with nice flat walls its something that you should consider before committing to internal insulation. Link to comment Share on other sites More sharing options...
Stewpot Posted March 7, 2020 Share Posted March 7, 2020 I would say it's a mistake to have cement render on a stone wall like that. The more I find out about lime, the more persuaded I am that this would be the stuff to use in this situation. You will certainly have lime mortar between the stones. Lime breathes (incorrect terminology, since no exchange of air takes place - it is vapour permeable) and that allows moisture to escape the stonework. Normally, moisture can get into the wall in three ways - penetration of rain from outside, rising damp from underneath, and condensation from inside. By sealing up the wall with cement render, you are seriously limiting the ways the moisture has to escape again - the result is damp walls. The moisture needs to be able to evaporate out into the air. I'm not against cement - damn useful stuff, but your house was built before it was in general usage, and building techniques need to be different to use it successfully. https://www.youtube.com/watch?v=eXykJ5odCRo https://www.youtube.com/watch?v=WGuvoDS0aN4 Link to comment Share on other sites More sharing options...
Cpd Posted March 7, 2020 Share Posted March 7, 2020 4 minutes ago, Stewpot said: I would say it's a mistake to have cement render on a stone wall like that I agree with you but for me I was to far along to to double back and use lime so made a big effort to make sure that the walls would have plenty of ventilation, it’s worked really well and the internal walls are bone dry. The original poster @MMeNDtal may be looking at what choices he has and if stripping the outside walls of cement render and then picking out the cement pointing and then redoing it all in lime and lime wash is not something he can afford or is unwilling to do then I wanted to provide an example of how I did it to show that it can be done, yes it’s not best practice by any means but in my specific situation it’s worked very well. Link to comment Share on other sites More sharing options...
Hobbiniho Posted March 9, 2020 Share Posted March 9, 2020 On 07/03/2020 at 13:20, ProDave said: Hi and welcome. We already have another member from Shetland @Hobbiniho I wonder which of you is the most northerly? hmm good question @MMeNDtal where are you? i would agree with what has been said 100mm frame filled with "kingspan", vapour barrier, service void then plasterboard. also on the coom celing make sure there is a vent gap at the sarking to allow ventilation behind the new wall, will probably need vents put in the roof near the peak, will need some carefull detailing to make sure downstairs doesnt have a howling gale coming in Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 9, 2020 Author Share Posted March 9, 2020 16 hours ago, Hobbiniho said: hmm good question @MMeNDtal where are you? i would agree with what has been said 100mm frame filled with "kingspan", vapour barrier, service void then plasterboard. also on the coom celing make sure there is a vent gap at the sarking to allow ventilation behind the new wall, will probably need vents put in the roof near the peak, will need some carefull detailing to make sure downstairs doesnt have a howling gale coming in I'm South end, currently! Down in Hoswick. Any particular type of vapor barrier you'd recommend? Link to comment Share on other sites More sharing options...
MMeNDtal Posted March 9, 2020 Author Share Posted March 9, 2020 On 07/03/2020 at 18:13, Cpd said: I agree with you but for me I was to far along to to double back and use lime so made a big effort to make sure that the walls would have plenty of ventilation, it’s worked really well and the internal walls are bone dry. The original poster @MMeNDtal may be looking at what choices he has and if stripping the outside walls of cement render and then picking out the cement pointing and then redoing it all in lime and lime wash is not something he can afford or is unwilling to do then I wanted to provide an example of how I did it to show that it can be done, yes it’s not best practice by any means but in my specific situation it’s worked very well. Yes, it's not really an option right now to remove the cement render. Possibly in the future. Link to comment Share on other sites More sharing options...
Hobbiniho Posted March 9, 2020 Share Posted March 9, 2020 2 hours ago, MMeNDtal said: I'm South end, currently! Down in Hoswick. Any particular type of vapor barrier you'd recommend? im in brae so im more northerly, if you use foil faced "kingspan" then you just have to add tape to the timber frame, but you will need to make sure it is fully taped everywhere, its a while since iv been in the trade so not sure what the most up to date method is Link to comment Share on other sites More sharing options...
Wildcat Posted November 28, 2022 Share Posted November 28, 2022 Hi @MMeNDtal, I would love to know how you have got on with your project. Starting a similar one myself 🙂 Link to comment Share on other sites More sharing options...
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