Soffits Installation

Anglia Roofline How To: Install SoffitsRoofline Replacement Step 3 – Installing New Soffits

After you have ripped out the old roofline and repaired the rafter feet (if needed) installing soffits is the next stage when replacing your roofline.

Soffits can be found in several areas of a property; they can be on a typical gutter run, a gable end or on a fascia only area beneath a flat roof.

You may find you need good carpentry skills to do the job properly.

What Are Soffits?

soffits under the roofline overhang
Soffits are the cover for your roofline overhang

Soffits are the covering you can see under the overhang of your roofline, next to the property wall (see picture).

Measuring Soffits

Below, I have described the three areas where your soffits may be on your property and how to measure for each location:

Fascia, Soffits and Gutter Runs –

Every property has a gutter run but you may not have a gable end as they are not always essential in the construction of a building. After studding out you need to find the measurement for the overall depth.

Soffits generally sit on top of the top course of face bricks and, sometimes, windows.

If your soffit has to butt to the wall then you must measure the depth from the wall itself and past the studwork / roof truss by another 5mm. Extending past the studwork / roof truss allows for a tighter connection with the lip of the fascia. You should also add a seal of mastic to keep out small insects such as wasps etc. If they find a gap you could end up with a wasp nest in your eaves – not an easy thing to get rid of.

If your soffit is layng on top of the face bricks then it is wise to allow 40 – 50mm past the wall and 5mm past the studwork / roof truss in the measurement. The excess on top of the wall means you do not have to seal the soffit with mastic as the area where the soffit meets the brick is too tight for anything to get inside. Bricks can shale in time and the cement between the bricks can become a little loose over time, so the deeper the soffit lays on the wall, the better.

Once you’ve established the depth it is time to prepare the length of the soffit before fixing. If you have a shower or oven extractors that needs to come through the soffit you can use a jigsaw to cut out the apperture you need.

soffits mitred at corner
Mitred corners on soffits look tidier

Also, bear in mind whether you want mitred corners., especially if you have a hip roof (a hip roof is a simple roof that slopes downward at all points at a uniform angle of pitch).

A mitred corner is usually a 45 degree cut, but always check with sample cuts beforehand. A mitred corner is not more structurally superior than running the soffit long – it just looks nicer.

Gable End Soffits –

Unlike the gutter runs, gable end soffits always butt up to the wall. The face bricks rise higher than the gable ladder as well so the only way you can get a measurement is from two points – wall to gable ladder. The soffits are fitted flush at both of these points. Be careful to make a neat cut as any strays in the cut will be easily seen.

The measurement for the length is found by the next two points, these are the gable ladder apex to a point past where the face brick stops. This is covered when the box end is shaped after the fascia has been fixed.

Gable soffits can normally be pre-pinned on the workbench to save time rummaging for pins whilst trying to hold the soffit steady. A seal can be applied to the point where the soffit meets the wall but it is not easy to do a neat job because of the angle of the face bricks.

Deep Soffits-

bays have deeper soffits
You will have deeper soffits in bays

Deep soffits are normally found on areas such as porches, garages and bay window areas. Soffit boards are normally between 300mm and 400mm in depth, although I have come across soffits as deep as 2m or more. If you have a deep soffit area it requires some patience because it is the most awkward part of your installation.

I’m assuming that you’ve already done a survey and checked what materials you need for the job.

A typical tongue and groove soffit is the best choice for hiding fixings, thermal movement and the general structure of the soffits. Flat boards are ok, but the joining strips can look out of place and the pin heads will be visible.

Take your time and take lots and lots of measurements so you know exactly what needs to be notched out after the first soffit board is fixed. It is generally the second soffit board that needs the finesse cuts.

You may have obstacles on your porches, such as gallows brackets, posts, wall steps and/or light fixings. You need to take special care with the measurements and cuts for these fittings, too many cutts and joins spoil the appearance of your property. After all, a porch is in use all the time and getting it right stops the ‘eye sore’ from being part of your daily life.

My fitters always take great care in these areas and, even after years of experience, they still find new challenges. You’ll often find that fixings are not built precisely so it is unwise to assume that everything is dead straight.

Make sure your cuts are precise; use the carpenter’s bevel and small set squares… 5 minutes attention to detail can save a lot of time and hassle.

Cutting and Fitting The Soffits

Now you’ve got all your measurements it is time to prepare your soffits ready for fitting, starting with cutting to the lengths you need.

marking soffits for cutting
Use a carpenter’s scriber to mark soffits ready for cutting

Use a scriber to make a mark along the soffit for the desired depth. Mark out all fixings (e.g. for your shower extractor) and finesse cuts such as mitres, bay windows and pipes. It may take a long time to do this and it is very easy to be disheartened if your soffits have many ‘ins and outs’.

It takes seasoned installers, like mine, quite a while to note down all the measurements that are needed to produce a well presented soffit.

cutting soffits
Cutting the soffit along the marked line

Use a sharp saw to get a good, clean cut on your soffits.

Once cut, use 30mm pins to fix the soffit to the studwork – and consider using ‘headless’ pins as these make a tighter connection when the fascia goes on next. If the run is more than the length of the soffit then a joining strip needs to be applied. Remember to leave a general gap between two lengths of soffits of at least 5mm to allow ‘thermal movement’ to take place without warping the soffits when they press together.


Bear in mind your soffits have no support, other than the fixings you use.

A poor fixing will make it droop, sag or even fall off.

securely fixed soffits
A securely fixed soffit

Every fixing must be tight and bedded into solid wood. Just because it looks OK does not mean that the job has been done to a good standard. Thermal movement across the seasons, year in year out, will test your fixings.

The next stage in your roofline replacement job (stage 4 of 9) is installing Fascias and Bargeboards.

Of course, following these steps is straightforward if your property is a simple layout, but if you have awkward extensions or glass-roofed conservatories then replacing the roofline yourself can become a bit of a nightmare!

If that’s the case for you, and you are in the Norfolk area, why not ask for a no-obligation, 30-minute survey and quote? You may be pleasantly surprised and – just imagine it – you can have the pleasure of watching someone else do all this work for you!

Related Posts:

Preparing Rafter Feet

Roofline Ripping Out

Replacing Your Roofline

Roofline Repair Tools

Roofline Nest

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