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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    I'm having a window and some French doors made for an extension. They are being made in Redwood and I'm thinking of using linseed oil paint to finish them which I'm hoping will prolong the life by avoiding getting any moisture trapped in the timber.

    The joiner who is making them usually treats softwood for use in external applications with Cuprinol clear wood preserver prior to painting. I'm wondering whether this will interfere in any way with the linseed oil based paint? I will be treating with linseed oil prior to application of the paint in any case. Should I let him treat the frames with the preserver or not?
    • CommentTimeJul 2nd 2007
    Pressure treatment is the only way to get a good penetration of preservative a quick dab on will be of very little benefit.

    Cant help with the cuprinol clear but I suspect it is solvent based and will mostly evaporate anyway.
    If the 'redwood' is larch, Douglas fir or a decent Scott's Pine then don't bother with the Cuprinol. Linseed oil followed by four thin coats of real linseed oil paint will do just fine. I use the Swedish made Alback, supplied by Holkham Paints.
    It actually says "top quality u/s red deal " on the quote. Any idea what that means?
    • CommentAuthortony
    • CommentTimeJul 2nd 2007
    The cheapest wood that they can buy in straight pieces
    Hmmm... the 'red' indicates better than 'white', but I'd want to know more if I was paying money for it.
    • CommentAuthortony
    • CommentTimeJul 2nd 2007
    Treatment is not necessary unless you are thinking that the window wood will be getting wet and here lies the problem. They do often gets wet by design! because of insufficient falls on flat areas, water traps especially where the glass sits, water designed to run into the joints especially in the sills, square dather than sloping down and out glazing rebates, no water stop or drip etc.

    I always drill holes in the members under the glass to let water out in the unlikely yet pretty well certain event of it getting in. I do not paint the underside of things behind the drip. This is mega important as it allows the joinery to dry out in the event of it picking up moisture.

    Microporous paints are just as porous to water as to water vapour so were a conn -- go with linseed oil paints.
    When it says a window is supplied "base coat stained", does this mean dipped in preserver (giving the timber that orange colour), or something else? I'm looking at some off the shelf joinery now as the guy who had previously quoted has informed me he is off on holiday for two weeks in a month's time and won't have time to complete my job until after he returns...

    I don't want any coating on the frame that is going to prevent me using the linseed oil properly soaking into the timber and me using the linseed oil based paint on it.
    Bl**dy craftsmen, always taking holidays! But hey, Chris, take a hliday yourself and go wih the flow :)
    Any advice on whether the "base cost stain" will affect the linseed oil treatment in any way (see my last post)?
    • CommentTimeJul 8th 2007
    "redwood U/S" means redwood unsorted, which weirdly means the best grade of redwood, certainly not the cheapest Biff! We used to find machine gun bullets in Russian redwood! No joke when putting it through the circ saw!

    Cuprinol or a straw coloured basecoat will not have any detriment on your linseed finish. It soaks into the cells of the wood.

    Not sure how good it is in principle for the enviroment.

    I use Kingfisher chemicals straw basecoat, google it.
    Cheers Richy, I was hoping that would be the case.
    I have had 30 years experience of treating exterior joinery for my own use. I would NEVER fit any external joinery, whether hardwood or softwood, without treatment with clear cuprinol or equivalent.

    Most paints and oils try to act as water barriers and fail - they merely obstruct drying out of wet timber. Presevatives kill the bugs that cause rot. Merely 'painting' on preservative is virtually useless. Water (the enemy which supports rot) travels up the grain easily, so the same route is necessary for preservative. All timber is naturally resistant to penetration across the grain. Stand a stick of dry timber in a bucket of preserrvative overnight, and be amazed how far up the presrevative is sucked, and right through to the core.
    The joinery must be constructed of dry seasoned timber using cascamite glue and immersed for 7 days in cuprinol - maybe one edge at a time if a window frame. (check other glues for solvent resistance). Drain off and leave to dry in a ventilated space for 4 weeks, after which you can paint etc as normal for decoration ( I have had no adverse reactions), but the preservative alone has a very long life without paint. Omitting paint can be a green plus as well as a labour and cost saving. It also means that 15 years later you can 'paint' vulnerable parts with a refresher dose of preservative in very dry weather for added surface layer protection.
    Not all timbers absorb preservative well: generally those most naturally durable tend to absorb least and vice versa - see info on the web.
    At the very least stand joinery overnight in preservative so that vulnerable parts have end grain immersed.

    If you need to construct a trough for immersion, a lead-lined trough made from planks is easily made.
    I have a window made of pine and some patio doors made from oak to treat/paint. If we decide to paint them then I've already got some good quality linseed oil and will give them a coat of that then paint with linseed oil paint.

    However, if we like to look of the doors, we might decide not to paint them. If so, what kind of oil would be best to protect them with? Also, how could we get the window looking the same colour as the oak without using a conventional stain? I was thinking about maybe applying an oak coloured wood dye and then oiling it with something for protection.
    • CommentAuthortony
    • CommentTimeAug 4th 2007
    Linseed oil is the perfect thing to use on the oak doors -- please dont use anything else.

    You could try making new windows from oak! Stain and wood dye are the same thing to me.
    • CommentTimeAug 4th 2007
    OS colour wood oils are a better finish than linseed as the linseed has a tendency to stay wet and attract dust when used on oak.

    Linseed is better for more absorbent woods like cedar.
    I always use linseed oil on oak.

    It depends on the linseed oil - it's not all the same. I find the Swedish cold pressed raw linseed that Holkham Paints supply is not only more expensive than most but it soaks in quickly leaving a completely dry surface next day that is not in the least bit sticky. I've heard tell, but haven't tried it, that the linseed oil sold as a feed additive for horses has similar properties at a lower cost.

    Matching two different woods to the same colour is probably a fruitless exercise as, even if you achieve a match, it won't stay like that. The two woods will change colour, probably at different rates. Best just take delight in the variety.
    So is linseed oil (I've got the Holkam stuff) a sufficient protection the oak doors (we are talking off the shelf so imported not English) and the pine window and, if so, how many coats and how often?
    • CommentAuthortony
    • CommentTimeAug 4th 2007
    The doors will need no more than the oil a few coats several weeks apart to start with then once a year possibly twice on the bottom parts.

    The windows I cant tell you about, but I will say that the best successes I've seen with these have been without any protection what so ever 50 yrs and still no rot compared to the rest of the houses around with yucky so called replacement windows!
    Depends a bit what you mean by 'protection'. A door from English oak, or from France and Eastern Europe, should resist rot for many generations without any treatment, but some American oak is not so durable. The colour will fade to silvery grey depending on how often it gets wet and how much sunshine falls on it. Oil will slow this process but won't prevent it.
    I think I'll apply just linseed oil to start with and see how they look (can always paint the window at a later date). They will be located on a south facing gable wall (single storey) but it has an overhang of almost a metre so that will give some shade and keep the rain off to some extent.
    • CommentAuthortony
    • CommentTimeAug 5th 2007
    I always drill drainage holes in the bottom member to let any water out again easily should it get into the glazing system. Also I never paint the undersides of frames, sashes or sills behind the drip either.
    I was looking at the Holkam website and it suggest using "shellac knotting solution" on the knots before painting but also on the rebates and the beads before glazing. Why is this? Is it necessary (because I'll need to order some)? Can anything else easier to obtain be used?
    • CommentAuthortony
    • CommentTimeAug 12th 2007
    Probably because they are worrying about water getting into the glazing system and wetting the wood and swelling it up causing their paint to crack and let in more water etc? Shellac will waterproof the wood but I would rather no water got in and if if did which it will, that it could get out again hence my drainage holes.
    There was sone comment about the linseed oil having an adverse effect on silicon in the glazing units??? What diameter holes do you drill Tony and at what spacing?
    • CommentAuthorbiffvernon
    • CommentTimeAug 12th 2007 edited
    Posted By: Chris WardleI was looking at the Holkam website and it suggest using "shellac knotting solution" on the knots before painting but also on the rebates and the beads before glazing. Why is this? Is it necessary (because I'll need to order some)? Can anything else easier to obtain be used?
    They are talking about traditional glazing with linseed oil putty. If you put the putty directly on the bare wood some of the oil can get absorbed by the wood leaving the putty chalk rich and oil poor. This is then more likely to crack and crumble. Painting the wood with shellac provides a barrier to this oil loss. Shellac ia an amazingly easy stuff to use as it dries very quickly. Your brush can be washed in meths or don't bother but use the same brush each time.

    Shellac will not waterproof the wood - in fact it is somewhat water soluble.
    I think the patio doors I've got are factory glazed so I've just got one window to fit and glaze with sealed units. Should I order some shellac and paint the beads and rebates then put linseed putty behind the beads or should I just use silicon? Would the silcon, if used, be adversely affected by the linseed oil?
    • CommentAuthorbiffvernon
    • CommentTimeAug 12th 2007
    No, dont mix linseed oil putty with sealed units. The putty is just for single glazing, the old fashioned way. What you need is glazing tape - a double sided sticky tape made of closed cell pvc foam. It comes in various sizes but for most domestic windows the 12mm wide 3mm thick stuff is probably what you want. Buy it from the firm that made your units. It comes in a 25m roll. I get it from Industrial Tapes Ltd, but they may not sell single rolls - you might have to get a big box of them which would be silly.

    You can add a bead of silicone on top of the edge of the tape for belt and braces protection.
    • CommentAuthortony
    • CommentTimeAug 13th 2007
    Chris, I do one 10mm dia hole 65mm from each side. On fixed glazing I angle the hole so it comes out under the cill but outside the wall.
    Found a tape supplier on the net Biff:-


    I'll give the drainage holes a try Tony, seems like a good idea.

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