I have just been back to take some photos of a house near Harlow which I sprayed earlier in the summer. It is a delightful timber-framed building dating from the 15th century. The owners of the property had to strip the building back to its bare bones to begin a very high-end renovation, whilst maintaining the character of the original building. They are connecting the original building to a small brick building at the rear to create space and light.
Hempcrete is the ideal building material for this kind of restoration as hempcrete is an efficient and cost-effective insulator. Using a loose fill material like hempcrete avoids the slow and wasteful process of using sheet materials in irregular shaped panels and eliminates voids. This is particularly important to exclude draughts and deter rodents from entering the walls. Hempcrete is breathable, and more absorbent than the timber framing. This means that any moisture in the building will be drawn away from the timber frame, preserving the frame indefinitely.
The hempcrete was spray applied so there was no shrinkage away from the timber framing. Spraying creates a much more adhesive hempcrete and it seems that the adhesion to the timber framing is stronger than the pull to shrink away that can sometimes be present in hand-cast.
The clients were so happy with the original work that they asked us to spray the adjoining brick kitchen at the back of the property as well. We have had some really hot summer days this year and already the clients were commenting how cool the house feels on hot days, even though the windows are not in yet!
This photo gives an idea of the deterioration over the years of the frame on the gable ends.
The following group of photographs show the stages of building from where it has been stripped back to the frame right through to its current stage.
You can see how bad the frame was in places and how the carpenters had to cut in replacement oak. The OSB board in the picture is temporary lateral bracing whilst the frame was repaired.
It is common to find black painted timber on these buildings and this was all sand blasted off to clean the timbers down. Unfortunately, the sand blasters were booked in before we were so all the timbers were clean by the time we arrived on site. The black colour of the studs in the picture above is the paint and the black in the photo below is where we have started to mask up the timbers with black masking. We always mask up the timbers before spraying, and as everything was so clean there was no room for error. Lime will stain clean oak so we usually like the sand blasting to be carried out after the hempcrete is done and before the plastering.
The French 3CM spray machine we use can be seen in the bottom right corner. It should be yellow and blue, but it has installed hundreds of cubic metres of hempcrete over the last seven years and has become a limey grey colour!
Here the hempcrete has been finished and the timbers unmasked to show the frame repairs. I am pleased to say that we didn’t get any lime on the oak work.
This building was beautifully plastered by hand, by Duncan Cowper. Here you can see that the plastering of the front wall is almost finished
The plaster used on the majority of our builds is Limecote, by Best of Lime, and it would be fair to say it is the best lime plaster I have ever used. The finish is beautiful and entirely appropriate for old buildings like this one. We never use sand-based plasters on timber buildings, particularly old ones. Sand-based plasters as you might imagine are a little ‘biscuit like’ and can easily crack out on timber-framed buildings that have an ability to move. This modern take on a traditional lime plaster is chalk based and so is much more flexible and forgiving, but is just as breathable. Some sand-based plasters have a very open surface and can allow significant quantities of water in during driving rain, but Limecote has a smoother more closed surface which reduces the amount of water entering the wall.
This shows the even texture of the spray-applied hempcrete and the hempcrete tight up against the timbers, meaning no air infiltration due to shrinkage.
I really like the photo below as it shows the inside of the upstairs gable. When we begin these projects there is so much decay, as was obvious in the photo of the stripped back gable earlier, and then we slowly reveal the beauty of the lime and oak. The bottom section has been plastered and the top is ready for plastering, as is the wood fibreboard insulating the roof. Note the rounded corners on the window reveals softening the look of the room. The hempcrete is up to 300mm (12 inches) thick in places here due to the frame repairs and chimney.
This is the far gable from the inside. The hempcrete here is around 150mm (6 inches) thick.
Here’s the brick building that will become the kitchen. It has been incorporated into the main building with what will be large glass walls. This building overlooks an old moat from a much earlier time. In the photos below you can see timbers embedded into the hempcrete to pick up the kitchen units. We fix timbers to the walls in kitchens so that the kitchen fitters can easily secure their kitchen units to the walls without going back to the original wall. The hempcrete stops short of the floor as this is not the finished floor height. We always leave the hempcrete an inch or so above finished floor level so if a there is a leak or the washing machine floods the floor, the water will not wick up the wall and stain the plaster on the walls. This used to be common practice even with plasterboard 30 years ago, but now very few people bother to respect this practice.
Here’s a video to give you a flavour of the work on this site, focussing on us spraying one of the kitchen walls. You can see me spraying the hempcrete onto the brick wall, using a straight edge to make it flat, and then a nail float to give it a final polish. It might look like not much is shooting out of the end of the lance, but every 35 minutes another cubic metre of hempcrete is in place.
I am sure there is lots more to say, but it is always difficult to know how much detail people want to know. Feel free to get in touch if you have any questions, use the contact form or leave a comment or just drop me a line to firstname.lastname@example.org. I am always happy to share.