How To Install Guttering and Downpipes
Your guttering has two tasks:
1) Catch rainfall from the first row of tiles
2) Quickly drain the water away to the outlet (downpipes and soak away)
You need to decide how far the rain has to travel and which type of gutter is to be fitted – for example, where you have a run over 10m you may need a shallow gutter with a steeper fall or a deeper gutter that can handle more water (assuming the fascia is tall enough to take a deeper gutter).
The ‘fall’ is the measurement by which the gutter drops to allow water to drain towards the outlet downpipes.
Many plumbers guidelines recommend a ratio of around 1:500 (which is roughly 20mm for every 5m of guttering). But it does depend upon the pitch and size of the roof above your guttering. The amount of water running off a steep roof, with hundreds of tiles, is very different to the amount of water that runs off a shallow pitched roof.
Tip: check how the original gutters were fitted to get some idea of what depth of fall/size of gutter you need to have.
Your gutters have a ‘high point’ and a ‘low point’. The difference in position between the two is known as the ‘gutter fall’.
The ‘high point’ is where the highest gutter bracket is placed and is the furthest from the outlet(s). If the run has two downpipes then the high point should be placed between them. The ‘low point’ is next to the outlet (downpipe).
The plumber’s guideline of a ratio of 1:500 should be fine.
As a rough guide: if your ‘high point’ is a bracket whose top sits 10mm from the top of the fascia height, then the ‘low point’ (placed next to the outlet) would be at least 30mm from the top over a 10m run.
Never fix a ‘low point’ gutter bracket with most of its mould off the fascia board. Gutter brackets that are positioned off-set on the fascia board will start to curl over time. A few millimetres is fine – but much more than that, for example over half the bracket, is very risky.
Make sure there is no overshoot on the ‘low point’ bracket position. Overshooting is where the water runs off the bottom row of roof tiles and misses the guttering. This happens when there is force behind the water running down the roof because the water leaves the bottom row of tiles in an arc, rather than just dropping instantly.
To check if overshooting is likely, set the ‘low point’ and pull down a roof tile to act as a guide of how the water will flow (see diagram below). Remember, though, extremely heavy downpours will normally overshoot anyway.
Installing Gutters - High & Low Point Gutter Bracket Positions
Determining Gutter Bracket Positions
You need to be absolutely confident about where the brackets need to be fitted. If you have to re-adjust a gutter run you will have screw holes in the fascia that may become exposed to the elements. Unlike wood, uPVC fascias cannot be ‘filled’ to a good standard and would have to be replaced.
Once you’ve fitted the high and low point brackets with 20 – 30mm screws, use a string line to decide the correct placement of the other brackets.
Wrap the line around the low and high point brackets. Make sure you have a nice tight string line with a good old fashioned ‘twang’ when flicked.
Decide which part of the bracket you are going to use for alignment, I normally use the top of the bracket as the alignment point.
If your top brickline (and fascias) are not level, then using a measurement ratio (as described above) may not be very reliable for achieving the correct gutter fall. So, before you fix each bracket, check the gutter is ‘falling’ correctly.
Hold a 1 metre level along the string line as still as you can. Check the level bubble sits slightly to the left or right of centre depending on which way the water needs to flow.
Fix the gutter brackets with a gap of around 800 – 900mm between each.
Tip: Mark out where gutter unions will be and fit extra brackets to support them.
Release the string line once all the brackets are aligned and firmly fixed.
Do another check with the level once the gutters have been clipped in. Plastic retracts in cold weather and expands in hot, so allow a little play for thermal movement.
One more final check:
Pour a little water slowly into the gutter at the ‘high point’ and wait. You should see it flow towards the ‘low point’ and drip continuously from the outlet or corner. If the water does not make it to the ‘low point’ or if there is any ‘pooling’ then the gutter installation will need to be re-fitted using a steeper fall.
The downpipes disperse the rain water to its final destination – the soak away. These are underground and placed away from the building’s foundations. If the pipes underground are not blocked and the soak away itself is the right size they will handle any amount of excess water. If the pipes are blocked or the soak away is small it will not cope with the water and your downpipe will be ‘charged’ – i.e. full of water. If your old downpipes were full of water when they were removed then it is best to get a specialist to take a look at your soak away before connecting the downpipe into it.
The Downpipe Construction
A downpipe has three sections: a swan, a pipe and a base.
The swan is positioned at the top. It is composed of two offset bends that link the gutter outlet to the wall of the house. Place the offsets against the outlet and the wall and measure the gap between them for the measurement.
The position of the base is determined by what the downpipe is feeding into; a soak away, a shoe or straight into a water butt. It will need to be placed and supported by a downpipe clip to prevent it from slipping off over time.
Warning– do not fix a downpipe clip below the damp course. Drilling holes below the damp course to fix the clip allows water ingress and can create damp problems in your home. If you do not know what or where your damp course is then it is best to get a professional to advise you.
The pipe is the last section to be installed. Measure from the base fixing to the bottom of the swan. This can be a very tricky measurement as it can be very long and there is nothing to hook the tape measure onto. Take your time and ask for help if needed. Once the pipe is cut and placed into the joining sockets use your 1 metre level to guide the pipe straight before drilling the fixing clips into the wall.
Connecting The Downpipes
Closing Up Your Roofline
After installing gutters the final task is to close up your roofline. There are 3 steps – ventilation, re-felting and fitting a birdcomb.
Ventilation – if you have used premoulded soffits there is no additional work and you can move straight on to re-felting. If not, then the ventilation method will be either porthole vents or over fascia ventilation.
Porthole Vents – each is a small disc that is a friction fit as long as the holes are drilled – I recommend drilling the holes every 500mm and between the trusses. Specially made drill bits can be used for this but they can be very expensive for a ‘one time use’. Drill the hole and then push the vents into the soffit so they snap into place. Continue along the run until the entire length is ventilated.
Over Fascia Vents – these are easier . They are nailed into the fascia using 50mm nails. Normally around 20mm high. Avoid installing them on corners as the fascia has a lot more load bearing on corners and can become weak if a ventilation strip is placed there. Go along the run, nailing down the vents on top of the fascia. Avoid leaving gaps between the vents as this can lead to infestations such as wasps and bees.
Re-felting – this is a crucial task because if done incorrectly it is the most likely area that will let water into your house. I’d advise you to use a hardlip tray or (most commonly known) eaves protector. You can use a DPC (damp proof course) but this is a very flimsy felt that can warp and belly. An eaves protector keeps its shape through the years. You can normally buy it in 1.5m lengths.
To install the hardlip tray, simply lift the existing felt, where it was cut, to expose the roof inside. Place the eaves protector on top of the roof trusses and allow the lip of the eaves protector to sit on top of the fascia. Pin down with at least 30mm pins and overlap each tray. If you do not overlap or put the tray underneath the felt you risk rainwater getting under the tiles and into the house.
Bird Comb – a well fitted bird comb prevents anything getting into your roof for the life of the fascias and keeps your eaves clear. If you have installed an eaves protector there is a small channel where the bird comb fits. Use 30mm pins to fix and don’t skimp; use a pin for every tile, as birds can be persistent and can sometimes flatten the bird comb if it is not strong.
Finally, replace the tiles and press down gently so the bird comb flattens in places where the tiles are flat. Some tiles may look a little ‘wavy’ as this is caused by the bird comb not settling. If they do not push down then let them lie so that they can settle over time.
Once all the tiles are down spend a little time making sure all areas are completely blocked by the bird comb.
Finishing up is mainly cleaning and carrying out a final check.
Clean the roofline area with ordinary glass cleaner. For more stubborn stains (such as pencil and pen marks) use solvent cleaners. An ordinary rag or tissue is good for the job and, when finished, your new fascias should look completely spotless.
Check for any areas that need seal of mastic, usually where brickwork is not so neat. Pay particular attention to the areas where the soffit meets the wall or the bargeboard meets the verge strip.
Do not make too big a seal as it can look unsightly and will make it harder to maintain a neat bead. The sealant will take a couple of hours to cure completely so do not clean the fascias again until it is completely set as you may smear the mastic.
Tip: Remember to give your higher windows a little clean before you break down your access equipment.
Installing gutters correctly is crucial when replacing your roofline. Incorrectly installing gutters can give you problems from minor inconveniences, such as occasional water overshooting, to more major concerns where your roofline is not watertight and internal problems such as damp or rotting timbers crop up.
Because Anglia Roofline specialises in roofline replacement replacement guttering and fascia we have experienced fitters who make 100% sure your property’s roofline not only looks good but also gives your property full protection.
So, if you have any doubts about your ability to replace your roofline successfully then why not ask for a free, no obligation quote? I take just 30 minutes to inspect the current state of your roofline and give you an honest report on what is needed and what it will be the gutter replacement cost. I don’t employ any pushy salesmen. Plus, if you can be flexible on when the work is carried out, you could save up to £825 off your quote.
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