Fitting Insulation to solid brick walls

LUHG1878

That's all the lath & plaster removed now, thankfully!

It has highlighted an unexpected issue that I will need to address first. There are wooden lintels above the windows, there are signed of rot, so i'm going to get all 3 replaced with new concrete reinforced ones.

I've also noticed that one of the loft joist has rotted at the end, all the others are fine, so will need to address that as well.

I've decided to batten the walls with 3x2, i'll then fit 50mm PIR board, leaving a gap between the brick and the insulation. I then plan to fit either a 12.5mm or 25mm PIR board to the room facing side of the battens, running perpendicular to the 50mm PIR boards. Then i'll fit the plasterboard on top.

This will give me a good 60-70mm of insulation, it will address the cold bridging issue, and it will also leave the airgap for the brickwork to breath.

I was quoted £5,000 by a local tradesman who came recommended, but I decided to do all works myself. So far i've spent £930 on materials, and £180 on a skip, and that includes all the timber, insulation, plasterboard, plus fixings. The only thing I have left to buy is the wood/mdf for the window facings and the alcove recess.

FreeBear

Wooden lintels are to be expected in many older houses - Mine is a late 1920s build, and it would appear that the builders had a large stock of 8x2 to use up.

It is worth getting yourself a roll of DPC to fit between the battens and brickwork - This will reduce damp from the wall rotting the timbers.

LUHG1878

Hi Freebear, I got 3 rolls of the DPC for exactly that. This might sound like a daft question, but where the DPC is going to be penetrated by the screws fixing the batten to the wall, should I be putting a blob of silicone or something there?

Our's is a 1920's bungalow, so they aren't carrying much weight, but I was surprised when I uncovered them, fully expected a concrete lintel. Hopefully it won't cost too much to get them replaced?

A.Penny.Saved

You should be aware that fitting insulation internally can cause problems with damp rotting timbers. Unless the job is done correctly you could end up with problems down the road with rotten timbers.

I thought about it a long time back with my no fines home. In the end I got the external walls fitted with insulation by an energy company who were doing the local area at the time. My home is a lot warmer and also cooler in the hot summers because these homes used to heat up like ovens when the outside temperatures were high.

LUHG1878

Hi A.Penny.Saved, thanks for the comment, it's a very good point, and one of the reasons why I am keen to ensure there's an airflow gap between the brickwork and insulation.

The walls are bone dry, so proper ventilation has prevented these problem for 100 years, hopefully that will continue to be the case.

We have a suspended timber floor, so air from there will be able to flow up between the brick and back of insulation. I also have good access in the crawl space, 6ft in some places, so i'll periodically check to see if there are any signs of damp or condensation, but I think (touch wood) it'll be fine.

External insulation is something we looked at, but it wouldn't be practical for us.

A.Penny.Saved

Where the insulation meets the upper timbers is where the problems often arise.

Damp coming from outside and condensing on the timbers enclosed by the insulation is one thing to look out for and protect against. Or at least read up on to ensure it does not occur.

dickibobboy

I did the same in my house, no cavity wall just two solid brick.

Instead of using timber frame we used metal stud wall frame around all the external walls in the house. I then used 50mm insulation between the frame which left a 20mm air gap between the insulation and the wall. I taped up all the joints then used normal 12.5mm plasterboard screwed to the frame and plastered over.

The floors are all timber suspended and there’s a loft at the top so hopefully plenty of room for air to circulate. If i do ever notice any issues i’ll have some air bricks installed on the outside to help but fingers crossed i should be alright.

I’ve not yet moved in but the rooms don’t feel as cold at the minute and they warm up and retain heat pretty well when the heating is on compared to a relatives house which is the same house just few doors down (which doesn’t have the insulation and has high heating bills in the winter! One reason i decided to spend on the insulation now while renovating)