Cost of roof replacement/renovation in Victorian house

Discussion in 'Sites, planning, self-builds and extensions' started by Sinbad, Nov 21, 2009.

  1. Sinbad

    Sinbad Guest

    I've found a house in Dublin that I want to make an offer on, but the slate roof looks like it needs replacing. Any idea how much this would cost? The roof is 50sqm approx. I think the actual structure is ok, just the top layers....any info at all would be great. Thanks!
  2. z101

    z101 Guest

    I had a problem with a roof recently and got a recommendation of a roofer from a friend of mine who worked with the chap during the building boom. The guy is actually fairly busy on new builds as he seems to have a good reputation. The first time he came he didn't charge me as he found and fixed the problem on the roof quickly but second time found very reasonable.

    I dont know the man personally but could PM you a number, and I'm sure he can quote you. I would be a stickler on tradesmen and he seemed very straight up.
  3. Sconhome

    Sconhome Frequent Poster

    Very often the issues with Victorian and Georgian buildings can be as a result of the combination of no DPC, untreated wood, no preservatives and insect attack.

    We recently uncovered a roof in a renovation project that on the purchase surveyor report showed no issues with the structure. Upon opening up the roof rafters were seriously damaged by old woodworm infestations and all of the rafter ends on the wall plate were badly rotten from dry rot.

    In the end the entire roof required new rafters to be installed and new wall plates to be inserted. It can, as in this case, be a situation where a house is brought onto the market as being "recently re-roofed". The slates / tiles can be lifted and new tile batten installed and re-slating done which gives the appearance of 're-roofing'. Unfortunately if the structural timbers are left undone, especially in a house of this vintage it can be an expensive error / oversight.

    To answer your question, the scope of works needs to be defined, at the least I would expect:

    Scaffold & access
    Strip / salvage roof slates
    Strip tile battens
    Strip felt / underlay.

    Allowing a reasonable amount of replacement slate you could budget in the region of €4-6,000.

    If you uncover problems, and I would expect them, you are talking about having to replace the roof structure and possibly ceiling joists with treated timbers. You would also likely have to replace the wall plates. Budget €3-4,000 for this.

    You may simply need a treatment by someone like Protim (out of business) for dry rot & wood worm which is approx €1000.
  4. Sinbad

    Sinbad Guest

    That's brilliant, not as bad as I thought. Thank you so much for your advice.
  5. onq

    onq Former user

    Couple of other points.

    People assume that modern treatments and details can be transposed into older constructions.
    Where these involve reducing the breathability of the construction, they can cause problems.

    Typical errors can include cement rendering over old brickwork filled with lime mortar. Cement render does not breathe like lime based products and will seal moisture into the construction leading to other damp problems, when all that may have been necessary to restore weathering ability was to rake out and re-point the brickwork.

    Regarding the roof, tightly fitting felt under perfectly flush slate layers can reduce ventilation, leading to problems for wall plates and roof timbers going forward.
    That having been said, roofs with no felt and/or inadequate valley boarding and lining can allow meltwater from our once-every-ten-years deep snowfall find its way into the attic space.
    Its not uncommon to find lime mortar reinforced with animal hair behind the slating in the attic - this traditional method of sealing can also reduce ventilation.
    When considering roof repair, give some thought to
    • increasing the width of the valley gutter
    • improving the "steps" in the covering to deal with both the issue of meltwater and reduce the likelihood of blockage,
    • widen the gutter to provide safer working space for roof maintenance.
    People assume that modern materials are suitable for remedial works, particularly slates and tiles.
    Where the weight, size, gauge lap and pitch are not a match for the original you can end up with; -
    • too great a weight of slate for the rafters or
    • too little lap for the detail to work correctly
    If measures are taken to improve weathertightness which reduce breathability then additional vents should be considered.
    Finally before you undertake any remedial work you should take advice from a building professional experienced or qualified in dealing with period houses.


  6. Sinbad

    Sinbad Guest

    Great, thanks for that:)