Roz Posted January 12, 2020 Share Posted January 12, 2020 (edited) Hello - sorry if wrong section. Our window fitters have filled in with foam around our oak windows in our granite barn. What do we put over the foam? Lime mortar as the rest of our pointing will be? If so, should we seal the foam with anything first? Many thanks Edited January 12, 2020 by Roz Link to comment Share on other sites More sharing options...
Mr Punter Posted January 12, 2020 Share Posted January 12, 2020 The foam is not waterproof so you need to cut it back a little and then use mastic to seal between window frame and stone. Alternative would be to cut back 20mm and use Compriband tape to seal. Link to comment Share on other sites More sharing options...
JFDIY Posted January 12, 2020 Share Posted January 12, 2020 Foam is Probably not UV stable either. You cut scribe and cut a capping strip to match the windows and hide it. 1 Link to comment Share on other sites More sharing options...
jfb Posted January 12, 2020 Share Posted January 12, 2020 I would cut the foam back a little and fill with lime. It is what I have done on my house with wooden windows and stone walls and it has been fine. Looks like pretty large gaps in places so you would use a lot of mastic if you go that route. 1 Link to comment Share on other sites More sharing options...
pudding Posted January 12, 2020 Share Posted January 12, 2020 Same with my house, builders made a plywood former and filled with lime, so there's a nice squarish profile covering the foam. 1 Link to comment Share on other sites More sharing options...
Roz Posted January 12, 2020 Author Share Posted January 12, 2020 1 hour ago, pudding said: Same with my house, builders made a plywood former and filled with lime, so there's a nice squarish profile covering the foam. Hi pudding, did they cover the plywood with lime? Link to comment Share on other sites More sharing options...
Roz Posted January 12, 2020 Author Share Posted January 12, 2020 2 hours ago, JFDIY said: Foam is Probably not UV stable either. You cut scribe and cut a capping strip to match the windows and hide it. So this would be a blue wooden end result, rather than a lime end result? Link to comment Share on other sites More sharing options...
Roz Posted January 12, 2020 Author Share Posted January 12, 2020 3 hours ago, Mr Punter said: The foam is not waterproof so you need to cut it back a little and then use mastic to seal between window frame and stone. Alternative would be to cut back 20mm and use Compriband tape to seal. I really wish they had used this tape on the tops of the windows, I assumed they would but they have just pushed them up against the top and then put just silicone to seal the tops on some, foam on others. So your suggestion is to have this tape to fill the gap where the foam is, then cover the tape with lime? Link to comment Share on other sites More sharing options...
Gone West Posted January 12, 2020 Share Posted January 12, 2020 6 hours ago, Roz said: What do we put over the foam? The traditional material used with stone is burnt sand mastic. https://www.womersleys.co.uk/shop/stone_repair_grouts_and_mastic/burnt_sand_mastic_10_litres 1 Link to comment Share on other sites More sharing options...
Roz Posted January 12, 2020 Author Share Posted January 12, 2020 31 minutes ago, PeterStarck said: The traditional material used with stone is burnt sand mastic. https://www.womersleys.co.uk/shop/stone_repair_grouts_and_mastic/burnt_sand_mastic_10_litres oh thanks Peter, my google search didnt bring this up! Link to comment Share on other sites More sharing options...
Stewpot Posted January 13, 2020 Share Posted January 13, 2020 13 hours ago, Mr Punter said: The foam is not waterproof I though PU foam was closed-cell. Link to comment Share on other sites More sharing options...
pudding Posted January 13, 2020 Share Posted January 13, 2020 18 hours ago, Roz said: Hi pudding, did they cover the plywood with lime? No, the plywood was a former/shutter, open at the front i think, into which they stuffed the lime, then took the wood off and brushed it up to look ok. Ended up looking like this - 5 Link to comment Share on other sites More sharing options...
Roz Posted January 14, 2020 Author Share Posted January 14, 2020 On 13/01/2020 at 09:52, pudding said: No, the plywood was a former/shutter, open at the front i think, into which they stuffed the lime, then took the wood off and brushed it up to look ok. Ended up looking like this - Oh I see! Very neat! Link to comment Share on other sites More sharing options...
Snowbeetle Posted January 27, 2020 Share Posted January 27, 2020 Hi Roz, We have just put mortar fillets over our foam edges exactly like yours. I had an old boy who has worked with lime for years give me a hand and he trimmed the foam back to give a neat face slightly set back / flush with window frame face. Then he pushed pallets into the foam at regular intervals (thin pieces of stone / slate - so it kinda looked a bit like he had pushed 50p pieces in). This gives a key for the lime to bond to. Then the lime was applied to cover the foam. Slight overlap with window frame - enough to seal it but as it didn't have a key to the painted wood not so much overlap that the lime would pull away from the frame. Cover as much of the reveal as you wish. care for the lime as you would normally as it sets. You can do the square set as in the pictures we had a tapered fillet as it was more in keeping with our old barn character. 2 Link to comment Share on other sites More sharing options...
Snowbeetle Posted January 28, 2020 Share Posted January 28, 2020 Sorry autocorrect changed gallets to pallets! Gallets = flat-ish pieces of stones used to plug into larger expanses of lime mortar to prevent shrinkage / give key. Sometimes they are used decoratively also sometimes covered over and unseen, depending on style Link to comment Share on other sites More sharing options...
Roz Posted January 28, 2020 Author Share Posted January 28, 2020 18 hours ago, Snowbeetle said: Hi Roz, We have just put mortar fillets over our foam edges exactly like yours. I had an old boy who has worked with lime for years give me a hand and he trimmed the foam back to give a neat face slightly set back / flush with window frame face. Then he pushed pallets into the foam at regular intervals (thin pieces of stone / slate - so it kinda looked a bit like he had pushed 50p pieces in). This gives a key for the lime to bond to. Then the lime was applied to cover the foam. Slight overlap with window frame - enough to seal it but as it didn't have a key to the painted wood not so much overlap that the lime would pull away from the frame. Cover as much of the reveal as you wish. care for the lime as you would normally as it sets. You can do the square set as in the pictures we had a tapered fillet as it was more in keeping with our old barn character. This is great info, I hadnt thought about popping bits of slate into the foam, thats a great idea. Thank you! Link to comment Share on other sites More sharing options...
Roz Posted January 29, 2020 Author Share Posted January 29, 2020 Hey @Snowbeetle or anyone else - when putting in slate sills under timber windows are we supposed to put in some kind of DPM? I hadn’t thought so as I didn’t know how this could work, but someone mentioned it to me and I notice the door has it, and the windows in our timber frame extension do too (no slate sills there though) Link to comment Share on other sites More sharing options...
Snowbeetle Posted February 4, 2020 Share Posted February 4, 2020 On 29/01/2020 at 08:04, Roz said: Hey @Snowbeetle or anyone else - when putting in slate sills under timber windows are we supposed to put in some kind of DPM? I hadn’t thought so as I didn’t know how this could work, but someone mentioned it to me and I notice the door has it, and the windows in our timber frame extension do too (no slate sills there though) We didn't as we are using all breathable materials and we took the view that the conjunction between a non-permeable material and permeable is where you are going to get water (condensed / vapour) potentially sitting trapped. We had a good look at the existing windows which had no DPM and there was no water ingress at all, so we decided that provided the fall on the windowsill was sufficient the water will only head out not in (we went for a 10% gradient but depending on if the sill faces prevailing weather / is very exposed you could do up to 20%). Obviously there are conditions of driving wind/rain which could, on odd occasions, mean some water thinks about going the other way, but with the window reveals being deep (giving some shelter from such conditions), the window frames being in good condition and pretty thick, the mortar around the window being in good condition and all the stones of the wall having an outward fall that there will not be a damp problem. We have no reason to regret this and the windows have been installed for over a year, through the seasons and we still have complete visibility of what is happening on the inside as we have yet to cover over the internal walls. HTH 1 Link to comment Share on other sites More sharing options...
Snowbeetle Posted February 4, 2020 Share Posted February 4, 2020 So I suppose, my answer would be that I don't think it is alway necessary but you have to consider the specific circumstances of the sill. My own choice is based on my circumstances so hopefully giving you my reasoning means you can see if it applies to you. Link to comment Share on other sites More sharing options...
Snowbeetle Posted February 4, 2020 Share Posted February 4, 2020 Just be careful when you put your gallet stones in the foam that you don't go right through it as that could allow the odd drop of water through. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now