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Replace roof: method and cost-price

A roof does not always have to be replaced fully, even when it is collapsing. Sometimes, it will do to replace or support certain parts of the roof construction. In the best case scenario, only the roofing needs to be changed. Here you can read more about roof renovation and the things a roofer takes notice of when judging the state of a roof.


replace roof - sagged purlinsWhat about sagged purlins?

The purlins of a roof may not start sagging. When this does occur nonetheless, this could have two possible causes: moisture in the timber or a collapse because of heavy overload or an incorrect construction.

Is your roof sagging? Rely upon a recognized roofer to replace your roof. You can easily compare prices on our quotation page.

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1. Damp rotten wood

When the purlins of the roof are affected by moisture or insects (woodworm, termites), there is no option but to renew them completely. Wood parts that are still in shape better get protected preventively as well.


2. Collapse due to heavy pressure or wrong construction

When the purlins have collapsed due to a heavy overload or a weak construction, it is not always required to replace the whole roof. A roofer can take measures to reinforce the structure by applying extra beams and shelves. The roof then gets aligned again. Whether this aligning is possible, also depends on the function of the space beneath the roof. If it is an inhabitable space, this usually won’t be causing problems. However, when the room is used as a sleeping room or a study, it is slightly more difficult to replace the roof.

example replace roof

Example of an old roof of which the support structure is in good condition. – Shutterstock


When should the wall plate be replaced?

The wall plate is the horizontal wooden beam just underneath the roof. It spreads the weight of the roof out on the underlying walls. This beam suffers greatly as it is attached to the wall and as such exposed to soaking moisture. A rotten wall plate can be changed partially. To do so, a part of the roofing and the roof sheathing get removed.

By means of stamps, the purlins get support and are jacked up a little, whereupon the rotten part of the wall plate is sawn and removed. A new wall plate is placed against the old one with a so-called halved joint. After that, the wall plate gets attached firmly to the facade with (chemical) anchors. If the walls are in bad shape as well, a so-called ring beam is cast in concrete.


replace roof gutterReplace or renew the roof partially?

In the best case scenario, nothing is wrong with the roof construction and it is enough to renew only the roofing. In general, roof tiles last for ten to fifteen years before they have to be replaced.

Is there no inner roof? Then it would be wise to still have this assembled. Not only does this save energy, it also protects the roof against moisture.

If the roof construction has been affected but the roofing is still in good condition, you might choose to recover the current roof tiles. However, take into account that this may sometimes be more expensive than entirely new tiles.


As it happens, the roof tiles have to be carefully removed and inspected. This is a labour-intensive job, as a result of which costs may rise considerably. If you are doing this job yourself, you can obviously save a lot of money. Moreover, it is surely profitable then to recover the tiles – if they are not too old at least.


Immediately control the rainwater drainage as well!

When inspecting a roof, a contractor will not only check the roof itself but also the state of the rainwater pipe. Depending on its condition, this will have to be repaired or replaced. Especially in the case of older houses, leaks often occur and entire parts of the gutter might be rotten. When renovating the roof, the gutter can easily be dealt with at the same time. This way, costs generally remain limited.


Re-roof over your current roof as an alternative

It is also possible to install a roof over your existing roof. This is especially the case when the slates of a sloping roof need to be replaced but the roof construction is still in good shape. Roofing (bitumen) and corrugated sheets are other possible foundations on which to install another roof. When over-roofing, the roof consists of roof panels that are manufactured from light alloy. These panels are placed upon wooden slats of the existing roof cover.

These works can be carried out quickly. However, this procedure will obviously change the look of the roof. The roof panels are neatly finished and available in many varieties, although you obviously cannot attain the same outlook of natural slates. Read here more about roofs over a roof.

replace slate roof

Example of replacing a slate roof. – Shutterstock


Cost to replace roof

How much does it cost to replace a roof? It is not easy to estimate the total cost for replacing a roof, as the price depends on the amount and sort of work that is required. On average, you can consider the following amounts:

  • Replace the wall plate (purlin roof with tiles incl. 3.28 feet roof sheathing): from £515 onward per running metre.
  • Replace roof tiles (without insulation): from £21.5 per square metre.
  • Replace slates (without insulation): from £26 per square metre.
  • Roof over a roof: £43 -£52 per square metre.


For a non-binding customized price, we would like to refer you to our quotation page.

Renew roof tiles

Completion of a renewed roof with red tiles. – Shutterstock