Stone walled problems & solutions

The normal problems you find with an unrestored stone built house are;

  • Almost nothing is entirely straight, so modern rectangular building materials require time consuming adaptation and trimming.
  • Humidity and damp problems throughout, especially if built into sloping ground and with the lack of a ground floor damp proof membrane a particular problem.
  • Woodworm infestations in all timber but especially pine and peripheral chestnut.
  • Poor to no insulation with especially the roof and ground floor a problem, and generally terrible thermal performance all round.
  • Narrow windows in deep walls giving uneven and insufficient lighting inside especially on the ground floor if built into sloping ground.
  • Widespread mould and fungus infestations and mouse tunnels and insect nests within stone walls.
  • Antiquated and unhealthy electrical and plumbing installations.
  • Inadequate (or no) heating systems.
  • No ventilation systems other than windows that only open full or not at all, and natural leakage.

It actually is often the case that it would be much easier (and sometimes also cheaper) to build a brand new house than restore an old stone built house to the level of a comfortable and healthy modern house, but there are three reasons why people continue to restore them:

  • They don’t realise this at the time they buy the house.
  • Rustic charms
  • And, most importantly, old stone built houses come with existing permissions in places where you couldn’t build a new house.

So how do you fix them to make nice homes which are comfortable, healthy and also reasonably energy efficient?
Solutions are given within this typical, in order restoration schedule.


Never start building work without a fairly detailed (ideally completely detailed) plan of your final building.

If you’re applying in advance for all your building permissions, as the law dictates, then you have no choice but to do this, but even for smaller, internal renovations that may fly under the official radar there should always be a clear and thorough plan.
This provides focus, gives a visual context for communication with builders, allows things to be checked as you progress, and allows electric and plumbing conduit and circuitry for the final system to be placed as you go.

It also allows you to ensure that materials are ordered and on site for when they will be needed so you don’t have workers hanging around with little to do or even disappearing to another job from which you struggle to retrieve them.

In short, a good plan will save you time, money and hassle and will produce a better final result.

Fix the roof

Stone walled buildings without an effective roof can collapse within just a few years. Additionally you need a dry shell partly because most internal building work requires one but also because drying out a stone walled building to make it suitable for modern living can take several years and so you want to start this process as soon as you can.

An unrestored stone house is likely to come with a timber roof structure of main beams, sub-beams and planks on top of the sub-beams.
This structure will normally be supporting interlocking clay tiles (not used for the last few decades and so normally towards the end of their lifespan now and not worth keeping) or traditional rough cut slates (which are an authentic and beautiful feature and also a good roofing material with a potentially very long lifespan, and so worth trying to keep).

Whilst better maintained examples of this type may seem like a decent roof, there’s a chance that the wooden structure has too high a moisture content and has become infested with woodworm, rot and mould, sometimes to the point where structural failure is a risk.

The main and sub-beams will probably be chestnut (sometimes oak). If the ends buried in walls have been exposed to moisture they may well be rotten and need to be replaced or repaired.
As equivalent new beams are very hard to source replacement is normally with a modern steel or steel reinforced concrete beam.
If a beam end is rotten the only repair option is to build a column bonded to the wall under the final good wood of the beam.

Old chestnut beams can be cleaned (horrible, dusty manual labour with a hatchet or similar and sander to finish …all normally made even more difficult by the presence of remnants of nails everywhere) of their outer 1-2cm of woodworm eaten wood to leave a very solid and beautiful core.
This core of aged hardwood can be treated with linseed oil to give a viable beam structure for a new roof that also preserves that house’s character and looks beautiful.

As doing this properly involves taking off the roof covering it’s generally a good idea to replace a clay tiled roof with a fibre cement board one (plus tiles) with rigid insulation and a breathable membrane between the supporting beams and the fibreboards.
If, however, you have a traditional slate roof or a very nice clay tile roof you may want to consider cleaning and treating what you can of the roof from the inside and keeping it as is.

Especially if you plan on sealing up the roof and finishing the inside to make living space, the fundamentally important things to do are to make the roof entirely watertight and to kill off all moulds, rot and woodworm with a suitable treatment.

This treatment can either be a painted or sprayed on insecticide (eg. Xylamon) or, if you want to try a less toxic approach, one of the borate based treatments available in the UK or other north European countries.
Galicians will often recommend that you soak all the wood in diesel, but this approach is at least as toxic as insecticide treatments, less reliable, and also gives your house a smell like the lorry section of a petrol station for up to 6 months.

If you keep the timber wood structure and don’t have natural ventilation passing over all of it then it is essential to guard it against warm, moist air from the inside of the house cooling and dumping moisture as interstitial condensation as it tracks past. For this you need a moisture barrier (eg. foil backed plasterboard, or, my personal favourite, cheap click flooring) on the inside of the wood structure and all insulation.

Finishing the internal ceiling isn’t something you do at this stage, as this comes after the house shell is watertight and electrics are routed. Additionally it’s good to leave the roof structure to dry thoroughly before you seal it up. You can and should hasten this process with dehumidifiers once you have the building airtight (although a traditional roof structure is not airtight, so if you haven’t modified this there is no point in running a dehumidifier).

If, as is normally the case, you are using the space below the roof structure for rooms (eg. bedrooms), then you need to consider how to keep them cool enough to be habitable during the summer.

Adding a velux window or two into a replacement roof provides better light (normally there will just be a single window in the gable end wall) and also ventilation. This will not be enough, however, to avoid uncomfortably high temperatures during the summer.

For this you need as much insulation as you can pack into the ceiling structure, and with a little creativity it is also possible to use formed fibre-cement boards to create chimney effect natural airflow that effectively self cools the roof.

Unfortunately the addition of velux windows changes a (non-structural) roof replacement from minor building works categorisation to major building works, which means an architect’s project. That said, a very high proportion of roof replacements seem to gain one or two illicit small veluxes and it never seems to cause a problem.

Fix the outer walls & expose to ground level

If the house is built into a hillside (and most are) then dig out (hire a man with a digger but don’t let him go right up to the walls unless you have complete confidence in his abilities!) the ground around the external walls to leave a decent air gap all the way down to floor level or below around the whole house …although do go carefully with this because sometimes walls need underpinning and digging them out without due care can lead to the building collapsing.

If you find unfinished walls (ie. earth where you would want stone) then you will need to underpin them small bit by small bit (so the wall doesn’t collapse) with steel reinforced concrete.
This is typically an issue in more cheaply built houses where some expense has been saved by only building an inner skin of stonework below ground level on the back and side walls.

If you have a road or another building too close to allow clearing down to floor level then a solution I’ve used is to go metre by metre digging a trench and inserting vertical fibre cement boards standing in a subterranean drain to form what is effectively an external cavity to the wall, with a damp proof membrane and drained surface protection above.

Whatever solution you come up with, the idea is that no (potentially moist) earth is in contact with any of your walls above floor level.

Retro-fitting damp proof coursing to a stone wall is a tricky business. The injection method used for brickwork doesn’t work for stone walls with rubble fill, and so really the only remaining options are adding one if you are underpinning or electro-osmosis damp-proofing (expensive to buy and requires electrical connection) otherwise. Galician soil does drain well though, and good granite is non-porous so this is often something you can get away with not doing.

It’s also a good idea to do any other remedial work to the outer walls at this stage, such as filling holes or removing render to expose the stonework. This allows plenty of drying time while you do the rest of the build. Optimally, fix the walls for the start of summer and waterproof them externally at the end of summer or in early autumn.

Waterproof the external walls’ outer face

You will read a lot on eco-building forums about lime mortar and letting stone breathe externally …but my personal view is that this isn’t an ideal solution for Galicia where the granite (except for the softer stuff in the south) has extremely low water permeability, the outside air is normally extremely humid and there are no hard frosts (at least near the coast).
You have to be careful that your pointing is a softer material than the stone of your house, but with at least the harder (and better for building) types of Galician granite even concrete is probably ok, although you would normally use a slightly softer, specialist product for pointing.

Instead I would advise waiting for a hot, dry spell in the summer to get the walls as dry as possible and then sealing the outer surface either with waterproof pointing if you have visible stonework or with a waterproof paint if the external walls are rendered.

Before doing this you should make any holes and make them good for passing ducting through for any chimneys, drainage pipes, electrics and ventilation vents/intakes that are in your plan.

Ground floor (plus ductwork)

If you have a traditional, unrestored ground floor (ie. a layer of concrete and tiles with no damp proof membrane or insulation) and especially if you want to move the existing ground floor walls around it is well worth biting the bullet and removing all non-supporting internal walls and then, if you don’t have enough height to lose 15-20cm to a raised ground floor, drill up the entire ground floor.
As you will only be taking out around 5cm height of existing floor you will need to dig down (maintaining a level) to accommodate the height of your new floor (insluation plus slab plus finish including any tile cement). If you find that the walls don’t go below existing floor level then you will need to underpin them.

If you can afford to lose 15-20cm to a raised ground floor, and bear in mind that this will affect the heights of all ground floor windows, doors and stairs (so normally it’s not viable with a stone walled building), then keep the existing ground floor as a nice level base to make a new one on top of.

If you don’t replace the ground floor then you will have a perpetually cold and damp ground floor and this will greatly reduce your building comfort and health. The best workaround for this is to fit a damp proof membrane on top of the existing floor (and bonded into the walls) with a click floor over the top of it, which will only take 1cm height in total. This will still get cold but won’t get damp, and also solves any radon issues.

If replacing the floor, once you have all traces of the old ground floor cleared out and have dug down to the necessary level you will be looking at a layer of compacted earth that you should level and compact as thoroughly as possible (it’s never too early to get things level).
Alternatively, if you can lose the height, you will have a level floor plate ready to build on top of.

To make a new ground floor the first layer you put down is rigid insulation. Complete continuity of insulation is important so laying two layers of 3,4 or 5cm (more is always better) tongue and groove insulation at 90 degrees to each other works well. You also need to fit insulation all around the sides to the height you will pour your new concrete slab to (normally 10cm if using regular concrete, but as low as 6cm is possible with specialist products). If you are careful fitting the insulation round the sides you can also use these sides as reference heights for levelling the slab when you pour it.

On top of the rigid insulation the next layer is the damp proof membrane, which sounds hi-tech but is actually nothing more than thick black builder’s plastic. If fitted carefully this layer also functions as an adequate radon barrier.
Builder’s plastic comes in widths up to 8 metres and so in most cases you should be able to do the whole ground floor in a single piece. You need to leave at least enough extra at the sides to cover the insulation edges and bond into the stone wall, but for additional protection against damp you can leave around 1 metre extra at each side (how this is used is described below).
Over the plastic goes steel reinforcement with feet to set it in the centre of the slab. If you are using conventional concrete then you will need to leave expansion joints in your slab. These can be created by setting thin (eg. 1cm) vertical strips of wood fibreboard in the slab and then either levering or angle grinding these out after the slab has set. If done carefully these can also be used as height references for levelling.

If you know the location of stairs and any support columns then add appropriate steel reinforcement that will protrude above the slab to be used as footings for these things.

If you have ground floor bathroom or kitchen plumbing (eg. drainage) that is best laid below floor level then this should be laid at this stage. Likewise, if you want to pass any electrics below floor level then lay the ducting for them at this point.
Be aware when you place plumbing and especially fragile electric ducting that builders will be tramping around unable to see where their feet are going when shifting and levelling the concrete for the slab, so place ducting and plumbing where it won’t get damaged (eg. cut it into the rigid insulation below the concrete slab) or protect it with suitable boards for the builders to walk on.

The next step to make your new floor is to pour the concrete, but if you are laying a new ground floor slab I would always recommend fitting underfloor heating tubing (eg. 16mm qualpex) into it.
The expensive way to do this is to buy insulation (put this layer above the damp proof membrane) that has the forming for pipework moulded into it. The cheaper and actually better way is to set the steel reinforcement at a slightly lower height (eg. 3cm in a 10cm slab) and zip tie the tubing to it.
The tubing should be laid without joints in the slab, in circuits for each planned room, none of which should exceed 100 metres in length, with sleeving where it crosses an expansion joint and at 10-20cm centres (depending on the heat of the water you intend to circulate in your system; hotter water = bigger spacings). 20cm, handily, is the grid width of standard steel reinforcement.
Plan carefully where you want your tubing to exit the slab, and label the pipes carefully!

Before you pour the concrete it is advisable to pressure test the underfloor heating tubing for leaks. Once that is done order a sand (not coarse aggregate) and cement (plus waterproofing additive and plastificant is recommended) load of concrete of perhaps 5% more than your calculated volume for the floor slab, and look forward to a merry few hours of concrete shifting and levelling.
It’s also a good idea to prepare a place elsewhere to use any leftover concrete (eg. an outbuilding floor or similar).
If you can locate a concrete supplier whose lorry has a good hose to get it directly where you want it then things will go more easily and quickly – this is worth paying extra for.

Once your concrete is poured and levelled leave it for several days (the longer the better, a few weeks if you can) applying a light spray of water on each of the first few days after pouring and ventilate the building as much as possible. Then, seal the floor with a concrete sealant.

Finally, bond in and trim off your surplus damp proof membrane. The higher you can take this up the inside of the external walls the better, as it guards against both rising damp and radon. If you plan to fit skirting boards of eg. 10cm height then use that full 10cm to take the membrane up the walls.
Even better, if the idea of half height (or higher) panelling or plasterboard finish, perhaps with rigid insulation behind, on the inside of the walls appeals, take the membrane as high up the walls as you can before bonding it in.
To bond the membrane into the wall, score out as deep a crack for it as you can, insert it into this and then mortar the crack in. You should also make sure to mortar the cracks of or completely render any stone wall the membrane covers for damp penetration resistance and, more importantly, resistance against insects and mice.

Upper floors (plus ductwork)

Traditional upper floors are of timber construction, but if your beams are damaged or inadequate, or just for sound insulation, steel reinforced concrete upper floors are the normal local method used in renovations.
You can put in a concrete floor above your beams to retain their character, but bear in mind that this will throw the levels of your upper floor windows and stairs out.

Steel reinforced concrete suspended floors can be supported by a timber structure or can be a shuttered pour with the reinforcement drilled into the exterior walls.

These are normally made at this stage, and remember to leave appropriate holes for plumbing and electrics if these haven’t already been fitted, and for ventilation ducting or chimneys if any are planned.
If you are installing bathrooms you will normally cast at least shower drainage tubes into the slab.

If you will be using a timber staircase then leave an appropriate hole in the upper floor, but if you are casting stairs in steel reinforced concrete then these are normally done at roughly the same time and protruding steel reinforcement should be left to allow the stairs to be bonded to the floor plate.

If you are making a timber suspended upper floor then this is also the time to install it. If you are using solid wood flooring you may want to leave sanding and varnishing it until later on the basis that any stains or dents from subsequent building work will largely polish out.

If you are making a suspended upper floor with structural chipboard flooring panels and click flooring or similar on top, fit the structural chipboard only at this stage.

Windows & doors

When to fit or restore the windows and doors is a tricky issue. On the one hand having an airtight building allows you to run dehumidifiers so that you can dry out the structure before applying finishes (which can take many months), but on the other hand you want to be sure that your shiny new windows and doors don’t get wrecked by subsequent building work.
Additionally there is also the consideration of site security; having an easily accessible site where valuable tools and building materials are stored is a risk.

Normally in a rustic restoration any existing windows or doors are timber, not airtight and are significantly degraded by mould and/or woodworm and hinge rust. As the pros of weathertightness and security outweigh the cons at this stage this is normally the point at which windows go in.
If, however, your project is fitted with single glazed aluminium windows and doors then any replacement is better done at a much later stage so as not to damage the new doors and windows.

Before fitting any window or door the hole it is going into should be repaired, squared and rendered as necessary. You should also ensure that the lintel is adequate and in good condition at this time, not, for example, a timber one part rotted by moisture.

If you want to protect new fitted windows on site you can fit a sheet of cheap chipboard (or cheap perspex sheeting if you need the light) on the inside. These things can normally be reused in some outbuilding later.


Normal Galician building technique is to bury all plumbing in the walls. As most plumbing these days is done using completely non-reactive (ie. doesn’t corrode from contact with cement or acidic water) plastic tubing, and as only higher, inland parts of Galicia experience hard frosts, burying the plumbing isn’t a bad idea.
If, on the other hand, you want to use copper piping and/or live high up deep in the Galician inland and aren’t in the house every day of the winter, then you may prefer visible or boxed in plumbing so that any problems or damage can be easily fixed without having to hack walls apart.

If you are rendering smooth or installing a false wall in front of stone walls then the plumbing is installed at this point with the appropriate mounting points for all plumbed appliances, sinks, etc.. Whilst many plumbed appliances are standardised or connected to plumbing points with flexi-hoses, it is still a good idea to have already bought the appliances to be used so you can check that the plumbing points are where they need to be for the actual appliance you will be fitting there.

It goes without saying that you should pressure test any plumbing systems before rendering over the top of them.

If you are keeping any plumbing that is already in place, for instance buried behind the tiling in a serviceable kitchen or bathroom, then be aware that the plumbing may well be using lead pipe. Lead is poisonous and has long been banned from domestic use in northern europe, but as flexible plastic pipe has only become available comparatively recently and as copper pipe comes in rigid sections which require connecting with (expensive, fiddly and leak prone) joints, Galician plumbers were still using lead piping (which can be moulded by hand) for awkward angles and connections until such time as they could no longer buy the stuff.
Fortunately, if you do want to replumb a tiled room without disturbing the tiles it’s normally quite easy to do from the other side of a brick internal wall.


Spanish regulations make a number of requirements for electrical installations, some of the most relevant to home installations being:

  • Lighting circuits must use 20mm conduit, 1.5mm2 wire, and have phase (brown, normally white for switched), neutral (blue) and earth (green/yellow) connections. A max 10 amp fuse is used with this specification.
  • Socket (10 amp) circuits must use 25mm conduit, 2.5mm2 wire, and have phase, neutral and earth connections. A max 16 amp fuse is used with this specification.
  • Ovens and other high power appliances have specific requirements according to their ratings.
  • All switches and sockets must be connected on a spur to the circuit via a junction box at the top (<50cm from ceiling) or foot (<50cm from floor) of the wall. The main circuit should run straight from junction box to junction box.
  • Bathrooms have exclusion zones around wet areas where electrics cannot be present.

You can find the full set of Spanish electrical regulations on the government’s website or, in a far more readable form, the principle ones for home installations in this very useful webpage from DIY store Leroy-Merlin.

Conduit is fixed to walls before they are rendered or can be jammed into cracks as best as is possible prior to pointing a stone wall. Junction boxes are also wall mounted prior to rendering.
As it’s far easier to pull electrical wiring through conduit before it gets fitted, you can also install all the wiring at this point rather than laboriously tugging it all through later on.

If you can’t bury the conduit in the walls, for example because they are exposed stone, then you will need surface mounted conduit and this job should be left until after the finishing plasterwork and painting has been done.

Electricians are expensive and using them to fit conduit is an unnecessarily expensive way of building. Instead, agree a complete electrical plan and materials specification with a registered electrician and then have the conduit (plus wires if you want) and junction boxes fitted by someone less expensive (eg. whoever is doing your plasterwork) before getting the electrician back in nearer the end of the project to connect up the fuse box and the fittings and give you your electrical safety certificate. Most electricians are happy to work this way, but of course always check first.

Rendering and finishing plasterwork

If your house had significant damp ingress, for example from a broken roof, before starting your restoration then you will need to get the internal walls thoroughly dried out before rendering them or applying any paint or wallpaper.
Fixing the roof and then having good ventilation for a whole summer is a good way to achieve this, but even then it is also a big help to run dehumdifiers (and some heating) once the house shell is airtight. Unfortunately 50-60cm width of stone and rubble does not dry out quickly.

Once you have adequately dry walls, render, a finishing plaster and then a plasterwork sealant can be applied.


Tiling can be left until after painting, but as tile cement can be messy and as tiles are by the nature easy to clean, tiling is normally done at this point.

Generally, but especially if fitting a tiled floor over an underfloor heating system, remember to leave an appropriate expansion gap around the perimeter of the floor.

Painting and decorating

Paintwork and decorative finishes should always be applied only to dry, sealed surfaces.

In Galicia it is generally sensible to use anti-mould paint. If you don’t, and especially if you use a matte paint with a textured surface, then you will need to be extremely careful to maintain a low humidity environment within the house in order to stop mould gaining a foothold on the wall.

Floor finishes and carpentry

Carpentry should be measured to exactly fit finished locations, and all possible sanding and varnishing should be done off-site.

As timber is easily stained by paint and wood very vulnerable to damage from builders and heavy materials, carpentry is normally left until this late stage.

Floating floors should also go in as late as possible for the same reasons, and these should have an expansion gap around the edges covered over by skirting boards.

Electrical and plumbing fittings and fitted furniture

The final work on your project is to fit the electrical fittings, bathroom fittings and kitchen furniture.