Roof Window WIP

[Fitzroy]

Updated 1st June 2018 - Showing WIP post 4 onwards!


Evening all,

On the to do list at some point is to repair the window in the small room in the roof as it leaks, the glass keeps slipping down and it gets bad condensation in the winter. So today i decided to take a look and start to think how easy or hard it would be to repair or if needed make, and fit, a new casement. So I swung it open, stood on chair to take a look, though 'oh i should take some pictures', got my phone stood back on the chair and CRASH. Oh cock i forgot i had closed it to go get my phone! Luckily having stuck my head through a plate glass window i escaped unharmed, save my pride, but rain was forecast and I now had a hole in the roof. Repairs moved rapidly to the top of the list!

Having taken the window out i can see that it's knackered and the entire lower rail is held in by rot and many many screws, window should have been replaced long ago! The window is built out of 4"x2" timber for the styles and top rail, with wedged through mortices at the corners. The bottom rail is made of a 4"x30mm (nice units) and tenon is formed using the top face of the board as one of the tenon cheeks, the glass was retained in the frame using glazing pins and putty. There is no rebate on the lower rail, i assume to avoid a water trap, however overtime (since 1875) the putty joint failed and the pane of glass slipped down leaving a gap at the top for water ingress.

Below are a bunch of images of the window reproduced in sketch-up. I plan to incorporate double glazing into the new widow, deeper casement and rebates and a fully bedded seal unit. My initial idea is to use the same design of no rebate on the lower rail and rely on the silicone adhesion to hold the unit in place. Window pane is 620mmx370mm. Stupid idea? Any other suggestions? Any other thoughts on the overall design?

Cheers Fitz

PS. So where do the drums skins come in you ask! This all happened today and no glaziers are open, so I bought some polycarbonate roofing sheet in B&Q and reglazed it with that and bathroom sealant. It is now raining cats and dogs and the window, whilst dry, is doing a great impression of a snare drum!

 

[RobinBHM]

I think if I was doing this, I would avoid any exposed timber on the roof.

One way to do it is by using an aluminium capping system.

http://www.questhardware.co.uk/glazing- ... ofile.html

It would need mitring at the top corners.

At the bottom edge a stepped, double glazed unit would be a good option.

Alternatively, replace the whole thing with an aluminium roof vent, although this may be tricky if its in a tiled roof

 

[Fitzroy]

And that's why I love this forum. Bloody brill idea from RobinBHM, not dear and I had noodled on if you could get such a glazed unit but without the name of it I had no idea how to search for it! Thanks. F.

 

[Fitzroy]

After two years on the drawing board this window was finally made physical! Building a roof window turned out to be more tricky/involved than expected, likely because like everything I make its over thought and over engineered. Any how for those interested here's the story.

The original window has a casement that folds down to sit over a raised box out off of the roof. The window box had to be replaced when found to be knackered when the top lead work was stripped due to being cracked, cue last minute 2hrs of DIY frenzy (no photos), and releaded by an amazingly skilled lead chap who dressed and welded it in to position.

To give you a flavour of what we are heading towards this is the new casement being located and screw positions worked out prior to installing glass and cappings which made it rather heavy.

The build starts from a piece of doug fir that I bought for making the windows in my shed, and this window, nearly three years ago. Board is marked up, broken down to size on the band saw, then planed flat and four square.

The design of the casement is based on a M&T frame with other elements glued on to it. I'm never convinced of my ability to measure things correctly so it's always good to get a first feel for what it'll look like and know you're on the right lines.

Next it's on to some joinery.

 

[Fitzroy]

The doug fir I had was rough sawn at nominally 2" (50mm) thick, which came up at 45mm thick once planed and thicknessed. My design required a 22mm rebate and I wanted to retain a 30mm section for the M&T joints. This is where I end up spending ages thinking about the thickness of the tenon and the position of the mortice. I know the rue of thirds but then when you are cutting material away for the frame rebates I get rather confused.

I eventually settled for 12mm tenons, with the mortices 12mm from the edge. This resulted in offset tenons and mortices with 12mm on one side and 21mm on the other. However 15mm of material on the thicker side would be lost where the glass rebates would occur, and I'd have to glue on extra material to get the required 22mm rebate.

M&T's were marked up (sorry no photos) and the tenons cut out on the band saw.

Trued up to constant thickness by passing back and forth over the table saw

Then flatten to remove saw marks with a little shoulder plan

Pleased with the resulting tenons

Tenons were cut to width on the bandsaw an pared back with a chisel. The top widow style is only 70 mm wide and I wanted to retain as much tenon with as possible, but I was concerned about blowing out the top of the mortice if I left it too thin. Reading around the subject a haunched morticed seemed to be the answer to this dilemma. The bottom style is wider so I could have a decent width tenon and retain plenty of material around the mortice.
Tenons completed for now.

Whilst I continue to practice with hand tools and I cut the first mortice by hand using Sir Sellars method it took me a long time and the results were not the best. The joint was solid and tight and internal shoulders look good but you can see the inaccuracy on the outside.

After this returned to machinery and used the drill press to hog out the majority of the mortices from both sides, then pared back to the mortice lines with a sharp chisel. This resulted in much better joints, which you'll have to take my word for as I seem to have lost the photos.

Putting the frame together is always anxious, will it be true, and flat and the joint lines come in nicely? Ooh, I'm pleased with that.

Once the M&Ts were done I cut out the rebates on the table saw, then made some fillets from the waste material. These were glued on to deepen the rebates to the required 22mm.

I foolishly had already rounded off and applied Custard's 'bum' edges on all the frame components so once I glued on the extra material it looked a bit daft. Not really an issue as all this is hidden behind the aluminium capping system. Which comes next.

 

[Fitzroy]

The capping system was suggested by RobinBMH, and bought for c. £60 for a 3m length, is designed for conservatories but my mind soon convinced me that it could be modified for use in my application. Mentally it was easy to mitre the thing up and fix it in place, turned out a bit more involved in practice but got there in the end.

I determined that the aluminium profile would require supporting to enable it to be cut accurately, I scribed the profile 'of the profile' onto a piece of scrap sycamore from the workbench build (another longer term WIP) and the used the table saw, and progressively raising and lowering the blade, to trim a stepped profile close to the line. A shoulder plane was used to pare the profile back to the line, and hey presto a cutting support.

The support was mitred on the table saw to give me a jig for perfect mitres. Originally I clamped the profile over the support, cut with a hacksaw and then filed the edge back to the support. This worked ok but was laborious, so back to the drawing board. After a bit of internet reading, some bravery and jiggery pokery with guarding and clamps to keep fingers safe I found I could cut mitres on the table saw, and made glittery saw dust.

Painfully I managed to cut one of the mitres the wrong way (doh) leaving one of the capping pieces the wrong length! I didn't have any spare material so I've ended up with an extra butt joint on one of the side caps, you can just see it lower right on the photo, ho hum!

The capping system is composed of an under-piece which seals on to the glass and the over-piece that snaps on to cap it all. A bit of thinkin and fiddling to get the screws located in such a way that the pulled all the parts together tight but it all turned out nicely in the end.

At this point the wife points out all the other roof windows in the area are grey not white, which in a conservation area may draw comments. Although the previous window was blue you can imagine some jobsworth rocking up and causing problems. So a quick rub down on the powder coat, some car spray paint, and a hey presto it's grey.

Next up it's putting it all together.

 

[Fitzroy]

The window design was a bit evolutionary as I thought about the critical issue of weather protection, potential leak paths and drainage. A roof window is much more exposed to the elements and with much higher water pressure due to the angle of rain impact. Unbelievably the finished window has 34 components, including the frame, draft seals, drip edges, under caps, over caps, seals etc etc. Perhaps that's why roof windows are quite expensive (especially bespoke sized ones) which is why I started making this to try to avoid a £1k bill, or making a larger opening for a standard Velux.

By this point I've cut slots in the frame for the draft seal and primed the frame with aluminium primer, which I really struggled with. 8mm drainage holes drilled in the bottom rebate of the frame should any water get past the capping system it has somewhere to exit the widow.

The casement was made based on the dimensions of the original roof box, which was replaced and releaded, the new one was fractionally longer, I think due to thicker lead work, and as a result the weather seal location was out by 10mm and became visible. A new slot had to be cut and the old one filled. Frame being painted up after filling and sanding, not the best job but will be unseen at the end.

Frame painted and with painted drip edges screwed on. These are not glued on as they will take the brunt of any weathering, on the original window these were rotted, so are designed to be replaceable. You can see the rebate for the hinges on the top edge, which is made of oak for strength/durability and attached with 6x50mm stainless screws, perhaps a tad over engineered.

Drainage holes had insect mesh poked into them to keep the bugs out.

Hinges are 102x67mm stainless 40kg rated, screws are all stainless to try to minimise corrosion. Hinges and weather seal in place.

The casement at this point weighed about 15kg, rather than 25+kg with glass and capping etc., also being able to stand through the casement to work out the screw location was a much easier approach. So took it to the roof and got all the pilot holes located and predrilled.

A squidge of glazing silicone down the edges, and the under-glass seals are placed on the frame.

cont next post

 

[Fitzroy]

the under glass seal is all that's required, but belt and braces a bead of glazing silicone was run to ensure a 100% seal for drafts.

After a good clean with meths the glass sits into place on the seal with some hardwood spacer blocks to keep it in the correct position.

My biggest leakage concern was the mitres on the top edge, water getting past these could get to the top edge of the seal unit and slowly work it's way past the seals. I bought some 0.7mm aluminium sheet and formed an internal cap so any water getting past the first cap would only be able to access the side drained channels or return to the top of the glass. Another Fitz classic of easy in thought and more difficult in practice, having to build myself a metal bender in the process, fun but more late nights!

The under-cap was screwed in place and judicious amounts of glazing sealant used around all screws and joints to try to keep water out.

The cap profile only extends c. 50mm down the side of the window, compared to the 75mm depth of the casement, so I used the aluminium sheet under the cap to cover the gap, I also formed a piece to provide weather protection to the hinges and deflect away any water running off the roof. These were stapled in place above the cap overlap.

Over-caps were snapped into place and glazing silicone used to seal the mitres.

The idea of the design is that if water leaks through the mitre joints it is deflected into the side channels where it drains down and out the bottom of the window.

cont next post.

 

[Fitzroy]

Finished window is pretty heavy so really glad I have all the pilot holes in place. As per advice from the lead man, lead sealant was injected in the pilot holes to provide a good seal around the screws . Lots of learnings along the way, but a fun build and really pleased with the outcome. Although it's not rained heavily yet so I still have everything crossed that the design works.

Rather a long post so hope it's been an enjoyable read.

Fitz.

PS: Yes I should have painted the exposed part of the lower window edge grey, but too late now so it'll have to wait until the 5yr maintenance check!