Doorstep Grille

Sub Floor Ventilation – Hallways

Period Property Sub Floor Ventilation

The Hallway

Walking along the high street in Bath, doing a bit of shopping, I couldn’t help but notice this hallway “vent” in one of the properties along the high street. Actually, it’s not one of the worse I’d seen but it struck me how much effort had gone into repairing the vent, which sadly had reduced its effectiveness considerably and how much nicer it would all look with a proper grille and a lick of paint on the door. I’m often drawn to the architecture and the construction and ventilation of the ancient properties in this lovely Roman city but it’s sad to see signs of neglect that create damp within buildings that have lasting consequences. Suspended wooden floors were the main battle against damp within the rooms of properties of the Georgian, Victorian and Edwardian eras. A solid floor requires a physical barrier to prevent moisture whereas suspended floors utilise dry air flowing underneath the floor boards . This air is fed naturally by wind and flows under the house, in one side and exhausting out the other. In a double fronted house, with rooms either side of the front door, the steps leading to the door quite often have a long cast iron vent grille that is essential to the health of the property. The grille allows the equivalent of 4 or 5 air bricks of air to ingress or exhaust under the hall and permeate beneath the living rooms either side. If this is blocked or has been replaced with bricks, plywood or a single brick vent then moisture can build up under the floorboards and lead to serious problems causing the underside of the wooden boards to become saturated leading to damp, wet rot and more seriously, dry rot. The hallway grille is part of a system of sub floor ventilation linked with air bricks at the front and back and possibly the side of the property designed to keep the property habitable and ensure the longevity of the building materials supporting the ground floor. When inspecting a property with rotten floor boards or damp in the floors ensure the sub floor ventilation is clear but also ensure that it exists or hasn’t been reduced. If in doubt as to the original layout of ventilation it can be a good guide to look at other similar properties in the street and see what they have, especially the well maintained properties. An extensive inspection of the ground floor vents and lifting of a few boards to check the sub floor cavity is clear would be the first place to start. Don’t forget to check the hallway vent !

this image, courtesy of Raven Housing Trust, shows just how destructive condensation can be

Preventing Condensation Part1


Here are our top 10 tips to reduce condensation……….


  • When taking a shower or a bath, keep the bathroom door closed and if there is an extractor  fitted, make sure it’s on.
  • Don’t forget to pull the plug and drain the water out of the bath as soon as you’ve finished!
  • Drying clothes on radiators generates plenty of moisture, it will reduce condensation considerably if you use a tumble dryer instead and extract the moist air outside.
  • Modern windows have trickle vents fitted to allow a little air to keep condensation down, if these aren’t fitted, opening the window just a tiny bit will help reduce condensation
  • Hob extractors are great for removing moisture but only if they are set up to extract to an outside wall and they’re used every time the oven or hob is on. If they’re the recirc type then they won’t remove any moisture, just smells – consideration should be given to extracting outside if condensation is a problem in kitchens.
  • People generate moisture just by breathing so the more people in the property the more likely condensation will be a problem – public houses, village halls, community centres, offices and properties with large families are particularly vulnerable so ensure ventilation is large enough for the number of people in the property.
  • Fix leaks – Check inside the house to make sure there are no plumbing leaks. Particular attention should be given to overflows , double check that overflow pipework is connected to the outside and works. Checks drains aren’t leaking under the sink and under the bath.
  • Fix leaks – Check outside that rainwater gutters are clear and downpipes are connected and not blocked. When its raining hard, go outside and take a look to ensure the rainwater is flowing away from the property and not soaking into outside walls.
  • Put the heating on – warm air holds considerably more moisture than cold air but don’t be tempted to seal up the house by closing every window, see next tip……..
  • vent vent vent vent vent – we can’t stress this enough but ventilation is the key to reducing condensation, combined with improving insulation, reducing damp and heating the property.

St Pancras Hotel, London

In June we took a tour of the fabulous St Pancras Renaissance Hotel in London and also the impressive station of St Pancras to explore the wonderful architecture and look for inspiration in search of new designs and ideas for products. Our guide, Mike, took us on the hotel tour, which is open to non residence of the hotel for about an hour and gave us a grand tour.


He explained the architect responsible for the building of the St Pancras was George Gilbert Scott. During the tour it became clear Scott would very much appreciate the castings we make at the Cast Iron Air Brick company as he too was a keen promoter of employing British foundries to make his goods. He loved to show off the products his  midlands workers could make to property owners in London, again, something we’re proud to do ourselves today!

Scott was a keen industrialist and revelled in promoting the skills of the craftsmen from the midlands in the materials used for his London designs. He incorporated not just the Quatrefoil design that we use in our “four clover” Quatrefoil channel gratings   but also Trefoil and even a “five clover” design rarely seen known as the Pentafoil . The quatrefoil can been seen at the top of the arches in the booking hall (below)


St Pancras was used as a show piece to show the gentry in the capital the splendid brick work, stone carvings and above all cast iron castings that his Birmingham and Derbyshire foundries could make.  What is particularly impressive is that Scott used ground breaking design to elevate the entire St Pancras platform. This ensured the hotel entrance aligned perfectly for passengers arriving by carriage yet allowed the train to depart on a slight fall to ensure the departing trains did so without making too much noise or generating too much smoke in the station.


The stunning main staircase featured flamboyant designs so Scott could show off all the skills of his workers and in particular the castings that the midland foundries could produce. In the example above, however, he tricked the guests into believing that the support, underslung along the stairs, was made of cast iron and was used to help support the structure. This support,  however, served no structural purpose as the stairs were self supporting and was made of a much lighter material, namely wood.  One reason, it is thought that the wood was painted to resemble iron was to help promote the skills of the foundries  rather than the skills of the carpenters!


Another ground breaking design that Scott incorporated into the structure was a fire main system to help fire brigades by ensuring the hotel had a huge reservoir of water. The water was collected by channelling water along intricate cast iron gullies and pipes and storing it underneath the building. (above) Cast iron pipes can be seen in the booking office  directing the rainwater into hoppers to storage tanks below.

aco with 5"

Upgrading Old & New Channel Gratings

Channel gratings, “Aco” drains, pavement drains, trench drains and French drains, whatever you know them as they’re the sort of long narrow drains you often see along the pavement or below door thresholds on footpaths or household patios.

Aco drain overhaul and new installations with cast iron grilles can be fraught with difficulty because matching the channel with the grating can be troublesome.

It is tiresome but if a cast iron grille is required to fit into an existing channel then it’s often more simpler to replace the channel as well to get a matching pair..

You see we use the 108mm wide Manthorpe Channel…


and then combine it with our 108mm Quatrefoil grille

manthorpe with quatrefoil

for a perfect fit !

However if you’re leaving an Aco drainage channel in place and fitting a new cast iron grille – then you have a problem…


The problem is the Aco system is 117mm (above) so it certainly won’t accept a 100mm wide grille (4″) and it looks even worse with a 5″ (125mm grille)…

aco with 5"

… and it won’t even accept our Quatrefoil gratings below

quatrefoil with aco

There are a few other channel systems available but again, if they’re not 108mm wide then they’re not going to be suitable for our Quatrefoil grilles and hardly any are exactly imperial widths so even a 4″ 100mm grille will be too small …

aco with 4"

So the solution is to install a new channel complete with new cast iron so the two match like our stunning Quatrefoil complete with Manthorpe system below

Quatrefoil Channel Grating

Quatrefoil Channel Grating

There is one other method were cast iron bearers  are used and a channel is formed out of cement and or concrete. Find out how we installed this here to create a walkway and bridge.

Using a conservation vent as a drain outlet on a period cottage, North Devon Wall

Improving Exteriors in Conservation Areas

Rainwater from down pipes used to emit from an open drainpipe on this old wall. It looked a real mess but what other alternative was there? Now, the pipe is finished off with a cast iron conservation 4 or 5 inch cowl, it looks neat, tidy and in keeping with this period cottage, North Devon wall

More details of the Conservation vent (item CON4 and CON5) can be found here

blocked slit grilles

Efficient Drainage ?

You would think that drain grilles would be capable of draining water away, wouldn’t you? Well unfortunately no, as these modern narrow slit grilles show. This is an all to common problem with modern channel gratings and one of the reasons we developed the cast iron Quatrefoil channel grille system.

The modern grilles shown in the photograph are excellent for not allowing stiletto heels to pass through but they’re not very good at draining away water. It is impossible to achieve effective drainage with narrow slits unless the water is clean and the grilles are removed regularly for cleaning. If that’s not the case and the water contains any soil or silt then the grille will quickly block rendering it useless.

Whilst our Quatrefoil grilles  won’t prevent stiletto heels falling through,  they will do what they’re designed to do and that’s drain water away – and they are perfectly appropriate for the grounds of listed buildings and period properties , unlike their modern counterparts !

quatrefoil part one

Installing Quatrefoil Channel Grating Part 1

Channel Gratings are ideal for collecting surface water along the lengths of pavements, drives and at the base of doorways and conservatories. Here we are installing a Quatrefoil channel grating at the base of a 2.4 metre wide garden step in the grounds of a listed building. Our system uses the Manthorpe plastic channel with our own cast iron grating that screws into the channel and can be used in conjunction with a junction box to allow L T and X shaped channels to divert water in almost any situation.

First*, clear the ground and sink a new drain pipe to take away the excess water. Here you can see we have used a fixed drain that will connect up to the rainwater drain for the house and take away the water. You can install a drain pipe that leads to a soak away or if you don’t want to dig down then you can leave one end of the plastic channel open so the water can be diverted along the surface . This can be done forming cement channels to divert the water down hill to a soakaway or to another drain pipe elsewhere on the property.

Connect up the plastic channels and lay the full lengths were they will be installed. Using a level, check the fall and ensure they are square. Cut the hole at the base of one of the channels were the water will drain into the drain pipe and fit the end stop (from the accessory pack) to prevent the water escaping out of the of the plastic channel. Lay a base of concrete along the whole area for the channels to sit in and then fit all the channels ensuring the other end cap is fitted at the end of the run.

see part two for finishing off

* our products are especially designed for listed buildings but please ensure you obtain  permission from the conservation department of your local authority if you are listed before starting the works

Installation of channel gratings

Installing Quatrefoil Channel Grating Part 2

Once the channel gratings are all in place, carefully mortar/concrete the pathway ensuring the fall is towards the channel and the channel falls gently towards the drain hole. It may be worthwhile placing the cast iron Quatrefoil grilles in position to ensure the concrete doesn’t distort the plastic channel.

Allow to set and then clean along the plastic channel rebates were the cast iron grille will sit. Ensure the leaf trap is in position over the outlet drain hole and then screw the Quatrefoil grilles onto the channel. If there are several grilles to fit, lay all the grilles loosely in position before screwing them all in place. There are very small differences in the dimension on all castings so it may be necessary to swap Quatrefoils around to get the best fit and get an even gap between each grille.

The finish of the bare metal grilles will quickly rust to leave a natural rusty iron finish. If a black finish is preferred then choose a painted finish. These grilles will last many years regardless of the finish because the iron rust forms a barrier towards corrosion with or without the paint. It is likely the cast iron Quatrefoil grille will be strong enough to support pedestrian traffic even 100 years after installation.

More details on the Quatrefoil Channel Grating

Further information on installing the channels

Junction box for creating T L and X junctions


Quatrefoil Square

Quatrefoil Junction Box

We’re pleased to announce the introduction of an essential grille that will really expand the opportunities for different layouts using our Quatrefoil channel grating system. The Quatrefoil square is an essential grille to have when using our Quatrefoil channel grates in an L, T or X shape. The junction box beneath the grille clips into the channel grating to allow for smooth drain water flow around corners. Examples and installation guides are available via the Quatrefoil square webpage

Offsetting carbon emissions caused by manufacture of cast iron products with the planting of 350 trees

Tree Planting – Carbon Offsetting

Melting iron to create our products uses energy either electricity or gas in large quantities. We keep the amount of energy used by commissioning only British foundries who, use energy as frugally as possible and meet EU emission standards with regards to pollution (unlike their Chinese counterparts).

But there’s no escaping it, manufacturing our products creates carbon and that’s a fact so to offset this carbon we’ve just bought 350 native British broadleaved trees to plant along 5 acres of scrub land around our workshops here in North Devon.

We’ll bring you updates on the planting and the trees as soon as we have them delivered in from local tree nursery Bowhayes Trees in Devon