Replacing cast-iron guttering with plastic


When a cast-iron guttering and downpipe system becomes too rusty to repair, you will have to replace it. Plastic guttering is easier and cheaper to fit in its place and needs no painting. Wear strong work gloves to handle the cast-iron, rusty edges can cause nasty cuts.

You will need Tools Ladder with a stand-off bracket, gloves, spanner, hacksaw, nail punch, claw hammer, rope, large screwdriver, small blowtorch, slim masonry chisel, string line and nails, plumb line, steel measuring tape, tile, drill with masonry bit, pointing trowel, filling knife, paint- brush, chalk. Perhaps a gutter notching tool and a wrecking bar.
Materials Plastic gutter, union pieces, brackets with 1in (25mm) No. 8 galvanized screws, stopends, gutter outlet section, downpipe, off- set bends, solvent cement, pipe clips with 1in (38mm) No. 10 galvanized screws, wall plugs, mortar for pointing, filler and paint for fascia board. Perhaps gutter angle, downpipe shoe.


The cast-iron sections, which may be 7ft-l0ft (2m-3m long), are very heavy and difficult to handle when you are standing on a ladder. Take great care and, if possible, have a helper to support each section and help you to lower it to the ground by rope.

Replacing cast-iron guttering with plastic
1.Try with a spanner to undo the bolts holding the gutter sections together. If you cannot, cut through each bolt with the hacksaw, then tap its shank upwards with a nail punch and hammer to free it.

2.Give sharp hammer taps at the joints where the sections meet. They will be sealed together with old putty or mastic.

3.Tie a rope round the middle of each gutter section as you free it, then lift it off the brackets and lower it to a helper who can steer it clear of windows and walls below.

4.Try with a screwdriver to undo the screws holding the brackets to the fascia board. If they are rusted in, heat the heads with a narrow blowtorch flame to expand the metal and break the grip of the rust. if the screws still will not turn, prise the brackets away from the board and pull the screws out with them. Use a slim masonry chisel and claw hammer to prise them off.

Replacing cast-iron guttering with plastic
5.Take out the pipe nails holding the downpipe lugs to the wall. Use pliers or, if the nails are rusted in, use a wrecking bar to prise the lugs away from the wall. Work down the wall and as you free each pair of lugs, remove the section of downpipe. It is slotted into the section below and can be lifted out.

6.Use the masonry chisel and hammer to take out the wooden blocks from the wall.

7.lf the downpipe goes directly into the ground to connect with a gully, break up the concrete or other surround to free it.


1.Repair the fascia board with exterior filler if necessary, before repainting it.

2.Repair damaged pointing where necessary.

Replacing cast-iron guttering with plastic
3.Nail a plumb line to drop from the fascia to the gully where the downpipe will discharge. Mark its position with chalk on the fascia and wall, then remove it.

Replacing cast-iron guttering with plastic
4.Fix a taut string line as a guide for positioning the brackets. Fit it as close up to the tiles or states as you can. Run it from the downpipe position to the farthest point of the guttering that will drain into it. This may be at the end of the fascia board or at an angle in the guttering. Check with a spirit level that the string is horizontal, and mark its level at the downpipe position with chalk. Then lower the string at the chalk-mark end by the amount needed to give the correct fall and fix it taut with a nail. The fall should be 1/2in - 3/4in (13mm-19mm) for every l0ft (3m).
Replacing cast-iron guttering with plastic
A long stretch of gutter may have a downpipe at each end. Fix the string line with its highest point in the centre and a fall towards each downpipe. If the outlet is in the middle of a run of gutter, fix string lines at both sides of it.


Replacing cast-iron guttering with plastic
1.Screw a bracket in place on the fascia 8in (200mm) from the mark at the downpipe position. Align its top with the string line.

2.Screw another bracket in place 6in (150mm) from the other end of the run of guttering, aligning it with the string line at the top.

3.Space out brackets equally between these two at intervals of not more than 24in (610mm).

ALTERNATIVELY, assemble the gutter on the ground and measure exactly the distance from the centre of the downpipe outlet to the centre of the union piece joining the gutter sections and from this point to the centre of the next union piece. Mark these distances on the fascia and screw brackets there, aligning their tops with the string. Each join will be supported by a bracket and you can then space out the brackets between at intervals of up to 3ft (1m). The measuring has to be very precise and it is often simpler to use more brackets.

Replacing cast-iron guttering with plastic
4.Clip the gutter, section by section, into the brackets, fitting union pieces where necessary to join the sections. Make sure that the sections are well pressed into place. Lodge the back edge of the gutter under the bracket clip first, then press the front edge down under the other clip.

5.The final section of gutter will have to be cut. Cut it on the ground after measuring off a piece of the right length. If it runs to the end of the fascia, let it extend 2in (50mm) beyond the end of the fascia board. Cut it with a hacksaw and smooth the cut with a file.

6.Use either a gutter notching tool or a file to cut notches in the gutter rims for the stopend clips to engage in. Fit the stopend, and clip the gutter onto its bracket and into the union piece holding it to the adjoining section.

7.If there is guttering at both sides of the outlet, fit the second run in the same way as the first.


1.Measure the length of pipe needed to slope inwards from the gutter outlet to the wall. Cut pipe to this length.

Replacing cast-iron guttering with plastic
2.Push the offset bends onto the pipe ends and hold this zigzag unit allow for expansion of the pipe in hot weather.

3. Clean and wash the pipe ends and the sockets of the bends.

4. With the zigzag section held together again, make a chalk mark along the pipe and onto each offset section to show the correct alignment. Take the unit apart.

5. Apply solvent cement outside the pipe ends and inside the sockets of the bends. Assemble the parts again, lining up the chalk marks.

6. Push the zigzag unit onto the bottom of the gutter outlet.

7. Hold a down pipe section in position over the bottom of the zigzag unit. See whether the top of the downpipe section is in line with a mortar joint. If not measure how much it needs to be raised. Saw off this amount plus 3/8in (10mm) from the bottom of the zigzag unit. The extra 3/8in (10mm) leaves a gap to allow for expansion of the pipe in hot weather.

Replacing cast-iron guttering with plastic
8.Mark, drill and plug holes in the mortar joint to screw the pipe clip into. The distance apart of the screw holes depends on the type of clip you are using. Hold the clip against the wall to make marks through the holes as guides for drilling.

9.Measure down the chalk mark on the wall to mark the position for drilling holes for the next pipe clip. You may have to cut the bottom end of the section of downpipe to align the clip with a mortar joint. Remember to cut off the extra 3/8in (10mm) again to create an expansion gap inside the socket.

Replacing cast-iron guttering with plastic
10.At the bottom, cut the pipe so that the shoe will be about 2in (50mm) clear of the gully. You may need to lift out the drain grid while you fit the shoe. If the pipe goes direct into the ground, allow enough pipe to do this.

11.Drill and plug holes for brackets between the joints of down pipe sections, spacing them equally not more than 3ft (1 m) apart and aligning them with mortar joints.

12.When all the holes are drilled and plugged screw the pipe clips in place.

13.lf the down pipe goes direct into a gully underground, repair the concrete or other surround.


Replacing cast-iron guttering with plastic
Ogee guttering does not rest on brackets but is screwed direct to the fascia board through its straight back. It is unwise to take It down without a helper. Once you take out the screws from one end, the gutter is unsupported and its weight will unbalance you.
Even with a helper to support the gutter section, it is best to work from a scaffold tower, which you can hire. Anchor the tower firmly before tackling each section of gutter.
Separate the gutter joints and remove the screws as for other types of cast-iron guttering.