Tips for painting double glazed wooden frames exterior and interior

[gunnag]

Hi All,

my house was built in 1989 and was installed with double-glazed wooden framed windows.

Over the years, the outside of the windows has been painted several times with gloss white and the end result after a few years is that the paint cracks, bubbles, lifts off and needs doing again. There is no rot so it seems worthwhile to try again using a better paint system.

This year I think I'm going to it myself, I'm planning on the following approach:-
- clean windows, use bleach to kill any mould etc.
- sand down to achieve a nice smooth surface
- mask off using frog tape
- use Zinsser Cover Stain before painting with 2 coats of Zinsser AllCoat Exterior Gloss (Solvent-Based)
- once the paint is dry, remove frog tape to get a clean finish, and use a glass scraper to get right into the edges

I'm going to use Zinsser cover stain and Zinsser AllCoat Exterior gloss (solvent-based) as I've used these before with good success. no cracking and peeling after 7 years so far.

For the upstairs windows, I'm using the same approach but using an access tower instead of a ladder. One variation is that I can unscrew the opening frames and take them into the shed for painting, this makes life much easier and saves working from the access tower.

Whilst I've got the access tower I might as well paint the facia and soffits. I have noticed one section of the soffit is rotten (about 1m ) so will need replacing, additionally, the facia soffit end box looks partially rotten as well, but I don't know how easy it is to replace these parts.

Does this approach for the windows sound reasonable any advice on how easy or not to replace soffit boards and end boxes would be appreciated, I'm reasonably good at woodwork but not too good working on access towers.

 

[opps]

Over the years, the outside of the windows has been painted several times with gloss white and the end result after a few years is that the paint cracks, bubbles, lifts off and needs doing again. There is no rot so it seems worthwhile to try again using a better paint system.

Bubbling could be indicative of the timber becoming wet. Often, but not always, where the double glazed units meet the exterior timber the sealant fails and lets water drip in. By convention, (AFAIK) they should only be sealed on the outer face to allow the units to expand and contract and not sealed inside. Sealing a double glazed unit in, and outside, increases the risk of the unit failing and misting (because the interior and exterior glass expand at different rates- putting the interior glazing bead under differential stresses).

Carrying down the upper units makes a lot of sense, for sanding... are you going to be able to carry them back up when wet?

I use Zinsser products but have never used All Coat oil based exterior.

The rotten soffit is rotten for a reason, I suggest you try to find out why timber (not subject to rain fall) is rotten. Look at the guttering and facia boards.

Photos will help others to advise you.

 

[gunnag]

Thanks for the response, I will post a pic of the rotten soffit tomorrow, I think the reason its gone bad is that either the down pipe (which is directly underneath) is blocked or that the gutter is badly fitted and spilling over, or a combination of both.

I think the challenge with the soffit is going to be cutting out a section squarely so that a new piece can be inserted and sealed. No doubt you experts have good ways of doing this.

Regarding bringing the windows down stairs to sand and paint, my idea was to let the primer and topcoat at least touch dry first before reinstalling. Luckily Its only myself and wife in the 3 bed semi, so we can move into different rooms when the windows are removed from one of the upstairs bedrooms. I guess I will need to polythene over the open hole whilst the windows are out.

Interesting that you mention about the seals between the outside and inside, I will have to take a close look at how its been done.

I've been very pleased with Zinsser paints for a number of years, I started with Zinsser Permawhite on another house and its held up for 10 years or more without cracking or flaking, I did find that its hard to get a smooth finish and is only available in satin so next I tried Zinsser AllCoat Exterior Gloss (Solvent-Based) which is a lot easier to apply and fairly easy to get a smooth coat.

 

[DiyNutJob]

If the paint is over the tape, the tape will peel the paint. Don't know what tower you have got. If you are 7 meters up, it will be too wobbly for any serious repairs.

 

[Notch7]

If you are fully painting and taking off sashes and doing in shed, I would suggest taking into account best practice for joinery design.

There are 2 main things which maximise longevity.

1) 3mm radius on all external edges: rounded edges ensures paint maintains full film thickness at edges. So if you have any sharp edges, it’s worth sanding them

2) on frames and sashes the joints should have V on them: that’s because timber expands and contracts and where joints are flat, it cracks the paint film. If a V is formed, that can have some V joint filler run into the joint, which is flexible.


Bear in mind solvent based paints which are alkyd based, once painted and cured the film will continue to harden over a period of years until it cracks.

Water based paint however remained flexible for much longer, however adhesion isn’t always as good and they have to be applied in warm conditions (above 12 edge, ideally more) or they wont cross link and moisture might get under the coating.