Build, Buy or Restore

[wobblycogs]

Hi folks, not been around these parts for a while but I see there are a few names I still recognize, hope everyone is keeping well.

Anyway, the title for this post is quite apt as I have a project where all three options are a possibility. We're looking at rebuilding an extension and the quote for the windows quite frankly made me cry and so I started to think about making the windows myself and I'd like to find out if that's a completely barmy idea.

Initially I'd just need to make three really quite modestly sized double hung sash windows (4 panes in each sash), lets say 1400mm tall by 600mm wide for the rough opening. In fact it's somewhat easier than that because at first I'd just need to make the frames so that the builder has something to put in the hole. They are going in a section of timber framed wall that will be rendered so the sash has to go in earlier than usual.

I've been reading John Birchards book on making doors and windows and so far I've not seen anything that's particularly frightened me. Clearly I'll need to work accurately and choose good timber if the windows are going to last and be reliable but the construction of the frames at least doesn't look that complex. The one big unknown here is building regs, my understanding is that the building control guy can sign them off in this situation, does anyone have experience of this? We're in a listed building so energy efficiency isn't their top priority and they may still insist on single glazing.

Is there anything I should think about before embarking down the make road? The buy road is, of course, open but I'd quite like to try and build them myself if I can. It's also possible that I might be able to salvage a couple of windows from what's already there but I won't know for sure till the wall is taken down.

Cheers

 

[RobinBHM]

Im guessing by the window size, they are sliding box sash windows?

Not technically very difficult to make but working out dimensions and setting out requires quite a but of knowledge -which Im sure there are a few joiners on here that could help.

Sliding sash windows are difficult to produce with double glazing as it is impossible to match the delicate sections of single glazed originals

You will are likely to have to submit section drawings as part of listed consent. If window details are part of the conditions, then this is a starting point for the window design.

I wouldnt do frames only and then make the sashes after -much easier hang the sashes and get them working first.

Accoya is ideal for box sashes, easy to machine the glazing bars etc, they stay perfectly straight.

Have a look at reddiseals and mighton websites for information on hardware -they may also have section drawings.

Allow tolerances for weatherseals for long lasting smooth running.

 

[wobblycogs]

Yes, they will be sliding box sash windows.

Fortunately the windows aren't going in an old part of the house and they are on the back so listed building will probably allow us to use one of the very thin double glazing systems. I'm not all that worried either way as it's not in the main body of the house so the heating isn't on there much. I'll be doing a full 3D design from which I'll produce section drawings. I've got a sample section drawing from a professional window maker so I'll make mine look like those.

That's a good point regarding fitting the sashes before installation. I was hoping to get away without making the sashes because one of the things we are getting built is a new workshop which would make that job a lot easier. In for a penny in for a pound though I suppose.

Thanks for the pointers on wood, hardware, seals etc. I've only just started to look into those aspects.

 

[Rhossydd]

I built all my own replacement sash windows at my last house. No real difficulties for someone with basic competency in woodwork.
The hardest part was sourcing bigger sash weights to balance the double glazed units.

I used Ventrolla draft proofing which was very effective and discreet, but it took a bit of convincing to get them to sell me any small quantities as they usually only sell to franchisees.

 

[wobblycogs]

Thanks for the info. I've been butchering wood for a few years so I'm at the stage where I know which direction to push a plane now ;-). I've read elsewhere that finding suitable sash weights can be a challenge so I'll start the search early. Did you have any problems with building control or any of the sign off side of things?

 

[Rhossydd]

Did you have any problems with building control or any of the sign off side of things?

As they were just replacements for existing windows to the same pattern, building regs weren't an issue.
Things may be different now or with a listed building or with a new build, so I'd suggest a phone call to the your local building inspector and ask their opinion. When I was doing my restoration project they were very helpful. They'd rather give advice in advance, rather than get involved with the unpleasantness of dealing with problems.

 

[Solicitus]

There are various companies you will find online who will produce sash weights to order in whatever weight you want. We had to do that when refurbishing double hung windows in our house recently.

Robert

 

[Rhossydd]

Architectural salvage companies or scrap yards often have a range of sash weights.

 

[HOJ]

In my experience, Building Control generally insist on compliance with current legislation, whereas the Conservation Officers are
there to protect, where possible, the existing situation, with a preference for repair/restoration, and have, on all my listed building projects
over ruled the BCO's

I try to get the CO's involved from the start and find that the more input they have the easier the project becomes, however they some
times make you jump through hoops, which can be frustrating, they can also raise certificates for a VAT rate reduction, which may be worth exploring.

With regards the frames, we make dummy units/former's for the builders to use for building up to, then remove and replace
with the finished items closer to the end of the build, keeps everything safe from damage.

 

[RobinBHM]

As HOJ says, dummy frames may be an option, as although you mentioned the walls are to be rendered, I would expect the boxes would butt up to the outside skin of brickwork rather than be set in between, so are effectively fitted from the inside. Of course you risk causing some chips off the edge of the render if you do it that way. Rendering may be done at the same time as the plastering so could be fairly late in the build anyway.

Fitting windows during a build can be soul destroying as unless they are really well protected they will be covered in building debris and dust will get in all the rebates etc.

Lead weights are needed for double glazed sash balances and available from Reddiseals. I would calculate the sash weight and work out the size needed before building the boxes to make sure you have enough room. Lead weights are available i 40mm, 45mm and 50mm square. Glass is about 2000kg/m3 and timber about 550 for softwood and about 650-700 hardwood (from memory at least!)

Technically you wont be able to provide the whole window u value, which should be 1.6 for part L 2010, unless you can test the window or be a member of certass or similar which can issue a certifcate for the calculation. It may depend on whether the extension is to be compliant with part L, or listed consent require certain period feature which then take precedence. If you have a listed property, the energy efficiency of the house will be so poor the extension, this is all a bit academic anyway.

 

[wobblycogs]

Thanks, I'll certainly look into fitting dummy frames during the build as I wouldn't want all my hard work getting bashed about.

My understanding with fitting sashes is that they are slotted in to a recess formed by the outer most skin of brick or block work and all the work is done from inside. These first three windows that I need to make aren't going into a wall built in that way though so I thought it best I dig out a picture as explanation. The lath you can see is the outer skin of the wall. The render is, I believe, cement but it may have a bit of lime in it. As you can see the wall itself is completely shot but now I examine the window a little more closely it may be possible to salvage it (I plan on having a closer look this weekend).

What I don't quite understand is how the render terminates at the window. I think the outside edge of the sash box (outer lining?) is aligned with the outside face of the stud work. Then an exterior trim moulding has then been nailed onto the sash box and the render applied up to that.

I think a better alternative would be to align the outside edge of the sash box with the render before applying an exterior moulding that sightly overlaps the render. The benefit of this approach is that I could use a dummy frame but the drawback is that the exterior moulding would have to be wider than the sash box (or the sash box could be partially exposed to the elements I suppose).

Do either of those sound correct?

 

[Phil Pascoe]

A better alternative would be to move house...

 

[wobblycogs]

After all the work I've done on this rotting pile of Georgian bricks and timber they are going to be carrying me out in a pine box. In fact I'm planning on living a very long time just to get my moneys worth out of the place! Good suggestion though and one that I have seriously contemplated on numerous occasions.

 

[Phil Pascoe]

Having owned a Victorian house for twenty years that did its damndest to fall apart for most of them, I know how you feel. The thing that baffles me is why people complete the project and then go straight on to another one :? .

 

[HOJ]

I think I would explore the route of repair/renovation, over replacement, which may cause more issues than is necessary,
also may negate the need to re render, which will just add more weight hanging on the lathes.

The top sash is missing the glazing bars so I presume has been reworked at some point, are the others the same.

We use the Repair Care system on some of our restoration work,including their Dry Seal putty replacement,
which significantly reduces the time needed to carry out any repairs.

 

[heimlaga]

I have made quite a few windows for renovation work. They have all been very slightly modernized replicas of the original windows made to look and function like the old ones but be less draughty.

In Finland traditional windows were hinged and upening to the side just like a door. Double glazing with double sashes have been the norm since the early 19th century. Outer sash opening outwards and inner sash opening inwards though most inner sashes had no hinges in order to save expensive hardware.

If I was to add double glazing to a British style sliding sash window in a historic building I would just add an inwards opening hinged sash on the inside with a single glass in it. The new inner sash would sit in it's own rebate on the inside of the window frame totally separate from the outer sash and it's hardware. Then the outer sashes and the outer part of the window frame could be made as exact copies of the old ones with old style thin glazing bars and everything looking period correct. All modern double sash windows always have the gaskets around the inner sash and some slight wentilation around the outer sash and this would come naturally with this solution.
To me this seems like a simple and elegant and fairly cheap solution........ which I have never seen made in practice.
Why not?

 

[wobblycogs]

Thanks HOJ, as far as the wall goes it's got to be taken down and rebuilt. The timber you can see in the picture is really badly gone but the bits at the bottom of the wall are, well, missing and I'm actually surprised it's not fallen down. The lathes seem to be in quite good shape for some reason and I suspect they, combined with the cement, are holding everything together. The whole back of the house is being re-rendered though so this small section doesn't add much. If I can repair what's there I will as I really don't need to go looking for work but I know there's at least one window in need of replacement as it fell to bits when I touched it.

Phil, I dare not tell the boss but there is a little part of me want's to start a new project once this one is finally finished. I've had to learn so many new skills in order to get this far with that it would be a shame to let them go to waste.