grade2 listed window renovations

[thehouseandnoidea]

Greetings everyone,

As the summer came to a close, we finally settled into our forever family home, if you could call it that – a Grade 2 listed Georgian townhouse. Like many others, we are fortunate to own a wonderful property but unfortunately have little knowledge on how best to preserve it. Therefore, we turn to you all in the hope of navigating through this project.

I am looking to commence restoration work on our windows this spring and have a couple of initial inquiries.

I've heard that linseed paint is crucial – would it be beneficial to start using linseed paint if it was not originally used?

My assumption is that unless we are willing to strip back to the wood and putty, we may not reap the full benefits of using linseed paint. Please correct me if I am mistaken

We have noticed a significant amount of mildew that has accumulated over the years on the internal glass frames, as shown in the picture below. I am trying to determine if it is growing on silicone. Could it be possible that previous owners have used silicone on the internal sides over the years?

It doesn’t quite seem like the texture of silicone, so I am curious if it could be something else.

Does anyone here have knowledge on this matter, and what advice would you offer for restoring it? Is it safe to remove it by scraping, and if so, what would be the best replacement material?

Thank you for any insights or guidance you can provide.

 

[TudorCottage]

It looks like some sort of plastic flexible filler and has been applied in a rather haphazard way.

I’ve tried linseed paint and just couldn’t get on with it. It takes an age to dry(weeks) and I wasn’t particularly impressed with the finish.

For window frames that I think are more susceptible to damp conditions inside or out I have made Bedec multi surface paint my go to product.

Over the last couple of years I’ve used various products and the Bedec longevity impresses me most and I will probably use it on all future projects.

I mask off the glass a couple of millimetres from the frame and run a bead of lime filler down the gap and paint over as soon as it’s dry. So far so good as any condensation or damp seems to evaporate before any mould forms. A wipe over of the frames and it looks like they were painted a few months ago rather than a few years.

 

[aockenden]

…run a bead of lime filler down the gap and paint over as soon as it’s dry.

What product are you referring to here out of curiosity?

To the OP, I’m sure you’ll get a hearty debate about whether linseed oil paint is CRUCIAL or not. We used it on our new timber windows late last year (although we’ve only actually primed them so far. Still waiting to finish up our finishing work on the inside and outside of the reveals before giving a second undiluted coat).

TudorCottage is definitely correct that it takes a long time to dry. Ours took a week for a balsam-turpentine thinned primer coat to dry. I expect the unthinned top coat we do next will take a bit longer than a week. That part is definitely a pain in the butt. Besides that aspect we thought it was easy to use, it goes a long way, looks pretty good, and I’m fully comfortable putting those materials into my house with my young son touching the windows and putting his fingers in his mouth, etc. I could not say the same about something synthetic.

Lastly, I agree that a lot of the selling points / advantages of a linseed oil based paint would go out the window (no pun intended) if you don’t strip the existing windows back to bare wood. If it’s layered ontop of an existing layer of some modern plastic paint, it can’t soak into the wood grain and it’ll blow off when the underlying stuff blows off the wood substrate regardless of how well it’s adhered to the plastic paint layer.

 

[Toby Newell]

Looks like badly applied mastic, I would remove. You can always add fresh. Bleach kills mold but the mastic looks poor. Putty is best on old windows.

Interesting. Never heard of using lime filler on wood! As long as the wood is coated (lime eats wood) It makes sense, water beads on silicone and would soak into lime and thus have a larger surface to evaporate faster, clever.

Linseed paint is certainly only crucial to people whose cognitive bias makes them assume everything 'natural' is best. There are much better performing coatings out there. Nothing wrong with it per se and nice sometimes to use traditional materials, but there are more durable, breathable coatings available. Linseed was incredibly cheap being an offshoot to the linen industry.

Some colours may still contain cadmium siccatives so I wouldn't advise eating it but at least whites should no longer contain lead. Gum turpentine is no healthier for you than dearomatised white sprits but at least it smells wonderful! If you don't mind the smell of turpentine and terebine (I love them) and the smell of linseed (much less keen) then go for it.

Like all 'drying' oils (conversion finishes is a less confusing name) they take several months to years to fully cure, in fact the surface layer next to the timber seldom dries fully unless left in a thin layer and exposed to direct sunlight. This is a feature, not a bug, and helps them remain plastic. Cured linseed is a natural thermoplastic polymer that is quite soft.

You are correct, you would need to strip back to bare timber to gain the microporous benefit. Your paint looks in quite good condition. You would normally gain the most advantage by stripping back and coating the outside with a breathable finish.

 

[thehouseandnoidea]

thanks for all your in-put, I will certainly go away and look at alternative options to linseed. We do live in the wet west and having a lenghtly dry period certainly can be a gamble at times.

The interior wood on the majoirty of the windows is in good shape it's just sorting out the horrfic job of the mastic/filler that has been used. I also would be keen to know what product @TudorCottage has used for the lime filler ... I will say the exterior woodwork is in a much worst state and the majority will require putty replacment and a good sanding back.

Thanks again, I'm sure I will be back once I start to tackle this looking for further advise.

 

[TudorCottage]

It’s called fine putty filler and I got it from Cornish Lime. It‘s not as flexible as normal putty but I find it easy to work with. It comes ready mixed and I just add some more water if I want it a bit more pliable. It drys very quickly and if I use it in warm weather I tend to mist it over with some water until it’s dry.

I give the frames a coat of paint then use the filler and then another coat on the frames and the bead of fine putty.

I never realised lime eats wood but I’m hoping this is over tens of years rather than a couple. I always repaint exterior frames every two years and interior between 2 and 4 years depending on how they look. I find it a far easier repainting frames that are tired rather than rotten.

 

[Toby Newell]

It’s called fine putty filler and I got it from Cornish Lime. It‘s not as flexible as normal putty but I find it easy to work with. It comes ready mixed and I just add some more water if I want it a bit more pliable. It drys very quickly and if I use it in warm weather I tend to mist it over with some water until it’s dry.

I give the frames a coat of paint then use the filler and then another coat on the frames and the bead of fine putty.

I never realised lime eats wood but I’m hoping this is over tens of years rather than a couple. I always repaint exterior frames every two years and interior between 2 and 4 years depending on how they look. I find it a far easier repainting frames that are tired rather than rotten.

Wet lime is about pH 12 and will leave plaster burns, cured lime is about 8.7, I'm not sure if it rises when wet but you should be ok for years, it actually has a mild antimicrobrial effect. It's more of an issue with repeated limewashing, but only on bare wood and small sections. It will just go grey or brown then start to weather. Lime carbonates quite quickly but Calcium hydroxide is almost as caustic as Sodium hydroxide, which is used to make paper pulp from wood chips. Seems like a clever idea, as is the prevention over cure method of maintenance.

It's more of an issue when dipping pine doors for example, people wonder why they sometimes come back shrunk, slightly warped with large gaps and loose glue joints. It's because they have sat in a steaming tank of wood dissolver for several hours.

 

[fernicarry]

The mastic bead rather suggests the putty holding the glass in place has hardened and crumbled away. You should check the outside condition as it could be much worse. Once the putty fails water sits in the glass rebate and rots it from the inside out. Tap the glass and if it sounds like a snare drum then the putty is gone and you'll need to sort that before thinking about paint.

Some people remove the glass and bed it into fresh putty. Thats the best solution but I've never been brave enough to do that since a lot of my glass is original cylinder glass. What I do is replace the failed putty on the outside and then squeeze new putty into the gap between window and glass from the inside.

Linseed putty (not to be confused with linseed paint), does take quite a number of weeks to form a skin before it can be painted. You can get synthetic replacements which I've used on a few windows but the texture doesn't look quite right to me. It does speed up the job enormously though.

Regarding Bedec MSP I started out using that but I find the externally it just doesn't stand up to the weathering it gets here. I still use it internally, mainly because now that I've started with my chosen shade of Old White on the woodwork I'm kind of obliged to keep going. Externally I now use Jotun Demidekk. I'm pleased to see that its come through this winter (winter is over, right?) unscathed whilst the MSP continues to deteriorate.

 

[Toby Newell]

There are many, mainly designed for outside, you don't really need them inside. I rarely do exterior paint work, a lot of people here rate Bedec MSP. I have used Sikkens products in the past. Search for 'microporous paint'. You should ask people with more experience.

My point was that linseed oil paint might be fun and romantic to use but contrary to lore, it isn't the highest performing finish, which is why approximately zero contractors use it.

Search for Sikkens Cetol and Jotun Demidekk, just for example, the former Dutch, Latter Norwegian. You will find a lot of the highest performing wood coatings come from Scandinavia, Bona, from Sweden, for example invented water based wood coatings.

This is quite obvious when you think about it, these countries have more severe weather than the UK, have long coastlines and more wooden bulidings.

Linseed oil is a pretty poor finish comparatively speaking. Now I must go and coat my furniture item with tung oil before I go to work.

 

[a twig]

Friendly moderator here - Before this gets out of hand I’d just like to gently point out that in Toby’s reply he had already provided a lot of information and options of routes for you to go down, and while the majority of his work is in interior timbers, he certainly is incredibly knowledgeable when it comes to all things wood and timber.

A simple search for any of those he mentioned on this forum would have given you a wealth of experience and information.

Can I politely suggest that as this is a forum made up of a mixture of industry professionals and passionate amateurs with experience ranging from months to decades, who receive no recompense for their extensive time and knowledge dispensed on here, a bit more care taken with tone when posting is always appreciated .

 

[Toby Newell]

As far as I am aware, we don't really do trolling on here. I studied materials engineering and have two City and Guilds, one in wood finishing. There is no 'go to paint expert' I am the finishing expert, we have a damp and pest expert, an ex brickie, a timber framer and many members who are quite knowledgeable on a wide range of subjects to do with general building, damp and lime for example. I have worked on hundreds of period properties for over 30 years, so as well as my technical knowledge I have seen what my clients have used and how that has worked out.

I did actually give two examples, if you aren't a troll maybe re read my reply, I gave two specific examples, products from Sikkens and Jotun.

This is a community, not a free AI type agglomerator. If you are patient and polite I am sure there are many people with experiences.

Malcolm and Twig run this site, for free, this is an excellent forum and resevoir of valuable opinion, experience and information. The search facility is fantastic and there are posts going back many, many years. The OP question is a fairly common one, if you spend a while searching I am sure you will find many threads to do with breathable paints.

Have a nice day.

 

[Toby Newell]

As I also said, in addition to two examples! One of which I have used the general consensus here seems to be that Linseed oil paint can work well but takes ages to dry and that Bedec MSP has been found to be a useful alternative, as I said, do some searches and you will find dozens of threads with different opinions which you can then use as a jumping off point for your own further research. FYI, if you have never heard of Sherwin Williams, it is a $23B turnover company and the 2nd largest paint manufacturer in the world after PPG.

 

[Toby Newell]

Seeing as I have been posting from the week this forum was created in 2006, you might find helpful posts of mine that explain the history of oil finishes, how they cure on a molecular level, how they were modified with metal salts and organic driers and how they morphed into varnish and paint. And also how they were further modified with alkyd and urethane forming resins.

Long story short, most microporous paints are some form of alkyd modified acrylic with added biocides, antimicrobial agents and UV inhibitors.

You may want to contact someone like Ingilby in Suffolk. Many of the UK's oldest properties are coated with their paints, they make both traditional lime, chalk, distempers and linseed oil paints plus hybrids and modern versions, I expect they probably have very good technical knowledge.

 

[TudorCottage]

As nothing more than an enthusiastic diyer my findings with Bedec have been nothing but positive.
For me it’s the closest water based paint I’ve used that goes on like an oil based paint. The beauty being no nasty smells, touch dry in 30 minutes and wash the brushes in water.

2 years ago I took one of our frames back to bare wood. I repainted it at the weekend, it took next to no time, I showed it some 240 grit sandpaper and gave it 2 coats. Completely unnecessary but made me feel good.

I’m convinced if you look at the frame you can see the air pass through the paint and dry the wood

We have sky blue frames and Brewers mix any RAL colour you like with Bedec MSP

No connections with either company just giving credit where credits due.

 

[Stevers]

Despite being sceptical of water based paints for any woodwork, I gave the water based Zinsser Satin Allcoat a try when I needed to smarten up my late father's model windmill before planting it in my garden. Frankly it was a revelation, and so much nicer to use than their solvent equivalent. There was no problem with keeping a wet edge and it flowed out beautifully to leave a semi-gloss finish. On the face of it a 'vapour permeable', self-priming, self-undercoating marvel - so yes there is some good stuff out there!

No connection with Zinsser except as a customer wondering if it could really last 'up to 15 years' - as the International Ranch Paint has done before it.

I have some hardwood greenhouse finials, a fibre cement greenhouse door panel, a softwood cold frame light (another dad production) and a sash window that will all be receiving the same treatment over the next year or so.

 

[Toby Newell]

Despite being sceptical of water based paints for any woodwork, I gave the water based Zinsser Satin Allcoat a try when I needed to smarten up my late father's model windmill before planting it in my garden. Frankly it was a revelation, and so much nicer to use than their solvent equivalent. There was no problem with keeping a wet edge and it flowed out beautifully to leave a semi-gloss finish. On the face of it a 'vapour permeable', self-priming, self-undercoating marvel - so yes there is some good stuff out there!

No connection with Zinsser except as a customer wondering if it could really last 'up to 15 years' - as the International Ranch Paint has done before it.

I have some hardwood greenhouse finials, a fibre cement greenhouse door panel, a softwood cold frame light (another dad production) and a sash window that will all be receiving the same treatment over the next year or so.

International, a British company, make fantastic coatings, Zinsser is like the Doc Brown of the coatings industry, always trying something new so they seem to come up with some very innovative finishes.

 

[Toby Newell]

As someone who has used thousands of litres of coatings, you do your research, read the TDS and MSDS, try and speak to someone at the technical department but at the end of the day, eventually, you have to experiment. Sometimes it's not so good, sometimes you find something fantastic.

I think it's also very important to understand how crucial proper preparation and application is in the equation. A relatively low performance coating can be enhanced and a top performing finish can be seriously degraded, depending upon how you prepare, how you apply and how much material you apply. The difference in performance and durability can be in the low multiples, ie you can often double or triple (or more) the life of a coating depending upon your application regime.

I think it's also important to understand that "it does exactly what is says on the tin" is the biggest lie in marketing. It is very rare that the technical instructions on "the tin" give the best result. Again, you have to use that as a guide yet not be afraid to use your imagination and common sense to try things a little differently. This especially applies to non industrial or non specialist finishes that are marketed to the 'end user' (ie not tradesmen) the golden marketing rule is 'do not make your preparation and application regime more thorough or time consuming than your competitors'. As an example, I know from experience that most film forming finishes on bare timber often require 5 coats where most product tin rubric would tell you 3 or 4 coats. Potential customers reading tins in stores might suppose any product telling them to apply 5 coats is inferior to the 3 coat product and so they buy the 'quicker and cheaper to apply' product. Don't be afraid to experiment, often the instructions are written for the lowest common denominator.

 

[Xeynon]

I'm currently restoring the sash windows in our place. For context, this is not my first rodeo, I've done about a dozen windows before. Up until now I've always used linseed putty to fit the glass. There's nothing wrong with linseed putty apart from the fact it takes absolutely forever to go hard enough to paint - at least a month. I don't really want to hang the window unpainted and with putty that hasn't dried.
I've looked around and come across Dry Seal https://surreysashwindowspecialist.co.uk/blog/putty-alternative/ which sells itself as a putty replacement. Does anyone have any experience of products like this? The last thing I want to do is screw up now after expending a ton of work restoring the frame.
I know linseed putty will work and will last a very long time. If there was some way of making it set in a day or even a week I would absolutely use it.

 

[a twig]

Not used it myself but heard good things about Arbo polymer putty, likewise the Dry Seal you mentioned.

Assume you are doing single glazing?

 

[fernicarry]

I don't really want to hang the window unpainted and with putty that hasn't dried.

The french doors I'm doing at the moment I primed all over including the rebate but only painted up to the rebate. The inaccessible bits got lots of paint whilst on the bench. I'll take them to be glazed with linseed putty next week. The Demidekk I use says it can take rain after 1 or 2 hours so a small weather window in a few weeks time should give me the chance to over paint the putty. I expect I'll have to do a full coat next summer to even it out but that's the cost of making progress at this time of year.

I have used a synthetic putty before, don't remember the brand, and it certainly works, but the surface finish just didn't look right to me. Too perfectly smooth, but with those little curls and bubbles you get from tooling mastics. Also a lot harder to clean off the glass than putty but that could just be me being badly prepared. Fair enough upstairs where it'll never be seen close up but not for these doors.

I also wonder how easily it can be removed should you need to replace the glass. One of the panes on these doors had been bedded into some sort of clear mastic and it was an absolute mare to get the dregs of it out of the rebate. Not that hardened putty is that much easier but it you catch it just right it pings off in chunks. Mastics tend to just stretch and then snap leaving little chunks behind tenaciously holding on.