Double Hung Windows

Double hung windowsByBen Everdell

In this presentation, I’ll explain step by step how too set out, construct and finish double hung windows, From receiving the plans, making a cutting list, machining the materials, construction of the frames, a setting out rod, transferring that too the styles of the sashes, mortice and tennon joints and the assembly of the components.

Step 1Receive plans of the windows too be constructed, first thing that is needed is your over all frame size, this will be the first component too be built. Once I have the plans I can work out my cutting list this will comprise of, heads, sills, Jambs and mullions. In this case, the mullions are going too be 44mm thick, the jambs and heads to be 40mm thick and the sills too be 60mm thick .

This is an example of a plan I would receive, I would make a cutting list as follow.1/ head 40x144 @ 22501/ sill 60x170 @ 22502/ jambs 40x144 @ 18002/ mullions 44x144 @ 1800Keeping in mind the thickness and width of the timber given is the finished size so add 10mm for ripping out.

Remembering before you start any work too have your PPE and tools you will need ready.

Using the cross cut saw dock the materials too length making sure too leave approx 200mm oversize too allow for any machining defects.

Once components are docked too length they need too be ripped down too width, using the rip saw blade on the panel saw, allowing 10mm oversize for machining.

Once your materials for the frames are ripped out, they need too be dressed down too correct sizes, in this case heads and jambs are 144x40, mullions 144x44. Leave the sills separate as they need a sill splay machined onto them.

The sill cutters are set up on the 4th head of the moulder, this being the top head. We have example pieces of the sill from previous jobs so we set the machine too match that. Once the moulder is set up you run your sills through and they come out looking like this. They have a small rebate before the 9 degree splay and that is for the bottom sash too be grooved over and is one way the window is protected against weather. Once the sills are run they need a drip put in the bottom.

Once all the materials are run you need too face mark and edge mark each piece, I also like to write, jamb and mullion, on there as well to make it easier to understand when your machine the materials further.Now get the head and the sill and on the head mark your overall width, then square that line across and come the width of the jamb inside of that mark on both ends, once you have that you need too mark out where the mullions go, so divide the gap between the two jambs and subtract the width of both mullions and this will give you where your mullions need too go. Once they are all marked out double check the measurements are correct too the plans and if so transfer the lines onto the sill, The lines just marked are too show where the trench has too be put. The trench in the head only has to be 5mm deep, mainly to help align the jambs and mullions, The sill needs to be trenched out the depth of the jambs and mullions, so 140mm from the back of the sill ( inside edge )

Once this is done you need too put in the grooves for the parting bead and the balancers, The parting beads location is set from a point on the sill ( where the sill has a small step ) and the position of the balancers can be worked out by coming out from the parting bead half the width of your sash style and centre your balancer groove there. I have a test balancer I use too make sure the groove is the correct size. The frame needs too have a parting bead groove in the head, jambs and mullions. Only the jambs and mullions need balancer grooves, most mullions will need grooves in both sides unless there is fixed sashes on one side.Once all the grooving is complete you need too cut the jambs and mullions too length, this is done by subtracting the thickness of the head after being trenched (35mm) and the thickness of the sill after being trenched (23mm) off your over all height and then cut your jambs and mullions too that length. Example if you had a window that was 1000mm high you would cut your jambs and mullions at 942mm.Once this is done you need too drill clearance holes in your trenches in the head and sill, lay frame components out on a bench making sure everything is correct and fits and then place glue on the ends of the jambs and mullions and place into the trenched out head and sill, make sure the edges of the jambs and mullions are flush with the edge of the head and the inside edge of the sill, (save lots of time sanding later on) then simply put two 75mm screws down through the head into the jambs and mullions, repeat same step for the sill, once is all screwed together clean off and excess glue and check frame is square. If its not square give it a push on the longer diagonals until it becomes square and the nail a brace too hold it square while the glue sets. Once the glue is set sand frames and cut off horns.

Once all of the frames are together stand them up out of the way and now your ready too get the sizes of the sash’s and start too construct them. The easiest way too work out the sash sizes needed is to get a frame you have just constructed and on the out side of a jamb up tight against the head draw in the top rail of the sash (55mm) and also draw in the bottom rail (80mm) on the sill making sure it is too the rebate before the splay. Now divide the measurement in-between the two lines you just marked and that will give you the centre line for the meeting rail (38mm) draw the meeting rail in. Now you can get the heights needed for the top and bottom sash’s, To find the width simply measure in between the jambs/mullions, this gives you the width, The sizes you have just taken down are tight sizes, for a double hung window you need too add 2mm in height to both the top and bottom sash, this allows the sash to be shot in later, and you need too also subtract 5mm off the overall width of each sash, making it easy too put into the frame later and less needs too be planed off the styles. This process can also be done by using a setting out rod and using the same measurements but I prefer too use this method.

Once you have all the sizes for the sash’s you need too make a cutting list and work out what materials you need, A cutting list will consist of – Styles – 55x44 (rip size 65x50)Top Rails – 55x44 (65x50)Meeting Rails – 38x44 (48x50)Bottom Rails – 80x44 (90x50)Test Pieces – approx 80x 44 (90x50) You need these too set up the morticer, tennor and spindle moulder, need 3 at 1.0.These are the section sizes I am using for this job, they may vary on other jobs depending on what the client wants, in this case the sections have too be 44mm thick as the glass being used is double glazing and needs a bigger rebate. Keep in mind when getting the materials for the sash’s too leave everything approx 150mm over length, Also very important is too make sure that your styles are long enough too have a 60mm horn. Now you need too work out the length and how many of each component you will need and then go and rip out your sash materials making sure to be as economical as possible.

Once all the materials are ripped out to size dress them through the moulder too the sizes given, Once this is done you need too face mark all the materials for the sash’s, this needs too be done for when you machine the materials further, Now get all of your styles and pair them up, making sure you have a left and a right hand style, number them so you know what are pairs. Now its time too mark out the styles for mortice and tennons.

The first step is too mark the overall height of the sash on the face edge, The top and bottom sash’s will be slightly different so you need too do them separately, Firstly get a pair of styles and they will be for the top sash. Mark your over all height, on one style ( making sure you allow 2mm bigger than the tight size measured ) now square those lines across. Get a top rail (55x44) and sit that inside one of the lines you just marked, Don't square this line across as you need too set that mortice line back.You need too set the mortice line back because the tennon is going too be in the rebate, This means when you machine your rails later you will take some of the tennon off, If you didn't set the mortice line back the mortice will be too big when you put it together, To work out how far too set back the mortice line you need too know the depth of the rebate your using, In this case it is 15mm ( usually is 12mm ) So from the mark of the width of the top rail on the style measure back 15mm and then square that line across, Do the same for the meeting rail. Now come 60mm from the outside line of the meeting rail and mark a broken line across, this is for the horn. Next is too put a haunch for the top rail, I like too make this approx a third of the top rail, mark this and square line across, there is no need for a haunch on the meeting rail so it can be a straight through tennon, Continue to square the lines just marked around too the other edge, Only square around the meeting rail mortice lines and the top rail mortice lines, ( Don’t square around the haunch lines ) Now clamp the other style too the one just marked out and transfer all the lines on both edges. These tennons will be split tennons so there is no need for a wedge allowance. Once the lines are on both styles place the rest of the paired, face edge up, styles in-between the two marked styles and transfer the lines too those styles, That is the top sash's marked out, Repeat this process on the bottom sash’s remembering too set back the mortice line ( 15mm )

The next step is too set up the morticer, tennor and the spindle moulder, first is the spindle moulder, for this job I am using an ovolo mould, So I set the cutters in a block and put it onto the spindle moulder, firstly the height has to be set. Using a test piece, I need a 30mm rebate, so that determines the height of the ovolo mould. The depth of the rebate has to be 15mm so I move the fences on the spindle moulder in or out until I get the correct depth, Once this machine is set up you can work out where the mortice and tennon joint goes.

The mortice and tennon joint is located in the rebate tight up against the ovolo mould. For this job because of the section sizes a ½ inch mortice chisel will be used. The mortice chisel size used is usually 1/3 of the thickness of the section size.Get a mortice gauge set it too the ½ inch mortice chisel and by using the test piece with the ovolo mould set it too the correct place, making sure you are setting it from the face side. Once the mortice gauge is set mark on the other two test pieces where the mortice and tennons go. One will be for the morticer and one for the tennor.

To set the morticer you need too put the ½ inch chisel in, Then using a test piece with the face side out, set the morticer so the chisel is going straight through lines marked by the mortice gauge, making sure the chisel is cutting square. Square two lines around the test piece and put a mortice big enough for the other test piece to go through, only go half way down when you mortice and then flip the test piece over and come from the other edge, making sure the face mark is still facing out.

The next step is too set up the tennor, The tennor has a top head, a bottom head and a scribing head. The remaining test piece is used too set this machine. Have the face mark up, use the clamps too hold the test piece to the sliding table and adjust the top and bottom head up and down until the tennor is taking off enough too leave the lines put on there using the mortice gauge. Get the test piece with the mortice in it and see if the tennon fits, You want the face edges too be flush and the tennon too be a good fit, Not too loose or tight. Adjust the tennor until you get this, It is much better too spend extra time setting this machine up correctly or you will have hours of sanding too do.

Now you need too set up the scribe head too suit the ovolo mould. This allows the tennon too go over the mould. This step is all about fine adjustment. The scribe works on the bottom head the best way too set this is too put the ovolo mould on the test piece with the mortice and keep adjusting the scribe until the joint goes together neatly, The scribe can be adjusted up and down and also left and right.

Now all the machines are set up its time too continue construction of the sash’s. Firstly the rails need too be cut too length using the panel saw. They need too be 10mm longer than the over all width of the sash, This is so that 5mm either side of the rails will come through the styles too allow it to be planned flush after the sash’s are together. Example: if the sash needs too be 650mm wide cut all rails 660mm long. Once the rails are cut too length the tennon line needs too be marked, to do this get one rail with the face mark up and mark 5mm in from one end, square that line across, now get a style, face side up, and place inside the line just marked and mark the width of the style, Don't square this line across as the tennon line needs too be set forward. The tennon line needs too be set forward the depth of the rebate, in this case 15mm, from the width of the style marked measure forward ( too the outside ) 15mm and square that line across. This has to be done to allow the shoulders of the tennon sink into the rebate, If this isn't done the sash’s overall width will be too small ( 30mm too small ) The line marked on the rail now is the correct tennon line, making sure there is a backing piece on the tennor, ( to stop the rails from blowing out ) place the rail on the table and clamp down, push through the tennor until the top head takes off the line marked, Now set the stop against the end of the tennon and then continue too put the rails against the stop and push slowly through the tennor, making sure too have the face side up, and too do both ends.

Once all the tennoning has been completed the next step is too mortice the styles, The styles are all marked out and all that needs to be done is set the depth of the haunch, set it approx 10mm past the depth of the rebate, in this case 25mm. The correct way too mortice is too start from either line marked and work in towards the centre, making sure that the mortice is done first and only going half the depth of the style, then using the stop on the morticer, do the haunch, again working from the line marked in towards the centre. Keeping the face mark facing out, flip the style over and put the mortice through the other side, making the mortice come all the way through. This can be done too all the styles.

Now all the components have been tennoned and mortised they need too have the ovolo mould, The styles, top rails and bottom rails can all be machined, the meeting rails need too be left out as they need different machining.The meeting rails for the top sash’s need only the rebate and not the ovolo mould, this is done using a rebate block on the spindle, The reason for this explained later, The meeting rails need a 20mm groove ( for the 18mm double glazed unit too slide into ) and the ovolo mould, this is done using a groover and a different set of cutters on the spindle, this is done because once the windows are together you are unable to put a glazing bead on the meeting rail of the bottom sash.

Now all the materials have been machined the next step is too clean out the mortises, mark and cut the haunches on the tennons, this is done by marking where the haunch on the style stops, placing the tennon into the mortice and transferring the line onto the tennon. Then measure the depth of the haunch to the flat of the rebate, then measure from the square shoulder of the tennon down the same measurement, this will give you the haunch that needs too be cut out, this can be done either by hand with a tennon saw or on the spindle moulder with a saw blade, mark and cut out all haunches on the rails.

Before the sash’s go together the horns have too be machined. Firstly the styles need too be cut 60mm past the bottom of the meeting rail. Once this is done the ovolo mould needs too be cut off from below the meeting rail, this is done using the cross cut saw and a saw blade on the spindle moulder

The next step is too put the shape on the horn, in this case it is a lambs tongue but the design may change depending on what the client wants, The easiest way too do this is make a template and use a copy pin on the over head router too get the same shape on all of the horns.

Now the sash’s are ready to go together, To start with put all of the sash’s together dry, Making sure the styles are paired up and the meeting rails are with the correct rail. Check the sash’s clamp up and the joints are neat and check the overall sizes too see if they are correct, If all is correct the next step is too cut wedges and glue up. Cutting wedges is normally done using the haunch off cuts. The wedge should start at approx 1mm and finish at approx 4mm for these sash’s the wedge should be approx 25mm long. Too split a tennon it can either be done with a 12mm chisel when the sash’s are glued together in clamps or can be done before glued up using a band saw too split the tennon. The second option is the faster way. Now the sash’s are ready too be glued up. One sash at a time take apart and place glue all over the tennon, making sure too cover both sides and the underside of the scribe, once the glue is on the tennons place the rail and meeting rail back into one style pushing in as far as possible, Put glue on the other end of the tennons and slide the second style onto the rails. Now lay the sash flat, by using sash clamps put slight pressure on the styles too make the joints pull up neatly. While the sash is in the clamps, put glue on the end of a wedge and smack it into the split in the tennon, do this too all the tennons. Take the clamps off ( the wedges will hold the sash together ) Clean the excess glue off and check for squareness. Do this too all the sash’s.

Once all the sash’s are glued up they need too be sanded, using the orbital disk sander with a 120 grit paper give the sash’s a sand, also once the sash’s are sanded use a hand router with a straight barring cutter too trim off the excess 5mm of tennon and wedge from the side of the styles.

Once all the sash’s are sanded the next step is too cut them too height on the panel saw, this is cutting off the excess styles past the top and bottom rails, The sash’s don't want any trimmed off the top or bottom rails at present so the aim is too cut the styles off flush with the rails. The top sash is cut square, The bottom sash needs a 9’ splay, the outside of the sash being the longest point.

Once the sash’s are trimmed too height the bottom sash needs a rebate and groove put in the bottom rail. This is too allow for the small step on the sill and for the foot of the balancer. On the meeting rails both sash’s need a 12mm filler put on. The filler fills the gap made by the parting bead, the filler also helps the sash slide up and down square as it is cut in between the two parting beads. The filler goes on the top of the bottom sash meeting rail ( to allow the sash too move upwards ) and the filler on the top sash meeting rail goes on the bottom ( to allow the sash too move downwards ) This filler is the reason the top sash meeting rail doesn't have an ovolo, it needs too be a flat too allow the bottom sash meeting rail too close tightly onto.

The sash’s are now ready too go into the frames. First the frames need too be beaded, There are 4 types of beads used in a double hung window. They are1 – Parting Bead, Used too keep the 2 sash’s apart and for the sash’s too slide on. ( 12x20)2 – Staff Bead, Used on the inside of the window, to hold the bottom sash in, also holds weather seal. (14x14)3 – Stop Bead, Used on the outside of the window, to hold the top sash in, also holds weather seal. (15x15)4 – Glazing Bead, Used on the sash’s too hold glass in. (12x14)

Firstly put the parting beads in, the get a 50mm spacer, This will determine where the staff and stop beads go. Place the 50mm spacer on the parting bead and then press the staff and stop beads tight too this, it is a 50mm spacer because the sash’s are 44mm thick and the needs too be a 6mm allowance for weather seal. The beads are fixed off simply with a nail gun. The stop beads can all be fixed off but leave one of the staff beads loose as that’s the only way the sash’s can be put in. The parting bead doesn’t get fixed off in any way.

Once all the beads are in place lay the frame down on a bench, (this makes it easier too check sash heights. ) Put the top sash in, and then place the bottom sash in, Making sure they are tight too the head and sill, The meeting rails should be flush with each other. If not take the top sash out and trim the top rail until the meeting rails are in line. There should be approx 2.5mm gap either side of the sash too the frame, if there isn't simply use an electric planer or hand plane too shoot the sash’s in.

Now the windows are all together the balancers and glass need too be ordered, The balancers we use come pre tensioned so too order them all we need too send the height and width of each frame and the balancers will come ready too install.When ordering double glazing, the glass wants too be 6mm smaller on the height and width overall then the tight sizes, Two people should check the measurements too make sure there is no mistakes.

The Glass and Balancers may take 7 days or more too come in, so at this stage if the windows are too be painted the priming needs too be done. The rebates and other places the painters wouldn't be able too get too when the window is finished are very import too prime at this stage, also if the windows require fly screens they would be constructed now, in this case the client didn't request screens.

The Balancers and Glass arrives and is ready too put in. Firstly take all the sash’s out of the frames too be glazed. To glaze a window with double glazing a bead of silicon around the rebate is needed, then place the glass in on top, make the gap around the unit the same, then fill that gap with silicon. The glazing bead is then pushed down tight too the glass and fired off with a nail gun. Do this too all the sash’s.The balancers should just slide into the grooves and have too screws too hold them in place, there is different balancers for the top and bottom sash’s but they are labeled.

The final steps are too put the glazed sash’s back into the frames, once the sash’s are back in the frame the balancers need too be fixed too the sash’s, This is done by a screw through the foot of the balancer into the sash. Once this is all completed the windows are ready too go too site, apart from the weather seal and that goes in after the windows have been painted, saves time for the painter.

That is my explanation on how too build a double hung window, I hope the information was easy too understand.BY BEN EVERDELL 3rd YEAR APPRENTICETHE JOINERY STORE

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