---
product_id: 50242069
title: "Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow"
brand: "ashbrook roofing"
price: "S$112"
currency: SGD
in_stock: true
reviews_count: 8
category: "Ashbrook Roofing"
url: https://www.desertcart.sg/products/50242069-pack-20-roofing-felt-lap-vent-stops-loft-roof-condensation
store_origin: SG
region: Singapore
---

# 3,000mm² airflow per vent Fits 400-600mm rafter spacing Easy tapered lead-in installation Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow

**Brand:** ashbrook roofing
**Price:** S$112
**Availability:** ✅ In Stock

## Summary

> 💨 Breathe new life into your roof — ventilation that works as hard as you do!

## Quick Answers

- **What is this?** Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow by ashbrook roofing
- **How much does it cost?** S$112 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.sg](https://www.desertcart.sg/products/50242069-pack-20-roofing-felt-lap-vent-stops-loft-roof-condensation)

## Best For

- ashbrook roofing enthusiasts

## Why This Product

- Trusted ashbrook roofing brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Effortless Installation:** Tapered lead-in design and 3 felt clips secure the vent even on degraded felt edges.
- • **Retrofit Ready Solution:** Perfect for upgrading existing insulated lofts to prevent costly moisture damage.
- • **Strategic Vent Placement:** Install in every other rafter bay near eaves for optimal cross-flow ventilation.
- • **Maximize Roof Breathability:** Each vent delivers a precise 3,000mm² airflow to combat condensation effectively.
- • **Universal Fit for Modern Roofs:** Designed to fit joist centers from 400mm to 600mm, ensuring seamless integration.

## Overview

The Manthorpe G630 Felt Lap Ventilator is a retrofit ventilation solution designed to increase airflow in roof spaces with lapped felt or membrane construction. Each unit provides 3,000mm² of free airflow and fits rafter spacings between 400mm and 600mm. Easy to install with a tapered lead-in and secure felt clips, it helps reduce condensation buildup caused by additional loft insulation. Ideal for professional refurbishments, it supports compliance with best practices for roof ventilation while enhancing attic space durability.

## Description

The Manthorpe Felt Lap Vent is a refurbishment product designed to increase the amount of ventilation into existing roof spaces. Usually fitted retrospectively to properties with additional loft insulation recently installed, however the Felt Lap Vent will help to combat the problem of condensation build up in any roof space with a lapped felt/membrane construction. The specifier should ensure that the opening of felt laps on the property will not adversely increase the wind uplift load on the tiles/slates or the driving rain resistance of the roof, for more information see BS 5534:2003, 5.8.1 & 6.2.1.1. - 3,000mm² airflow per G630. - Can be fitted at joist centres ranging from 400mm to 600mm. - Easy to fit, the tapered lead in helps to slot the product between the felt laps. - The 3 felt clips help secure the product in place even if the edge of the felt is degraded. Installation: - Initially it is recommended that one ventilator be placed into the laps in every other rafter bay, down at low level (as near to the eaves as possible) and on both sides of the roof space to ensure a cross flow of ventilation. - In extreme circumstances, additional ventilators can be positioned in the vacant felt laps to increase the overall amount of ventilation provided. - Only one product should be positioned into a single felt lap. If additional vents are required, then more vents can be placed into the other felt laps within the same rafter spacing at higher intervals. - The product can be installed in roof spaces with rafter spacings ranging from 400mm to 600mm. - Each unit will provide 3,000mm² of free airflow into the batten void. - For further information on the recommended ventilation requirements for roof spaces refer to BS 5250 Code of Practice for Control of Condensation in Buildings.

Review: Absolutely Excellent (so far), but expensive. - Hadn't been in the loft for a couple of months so was really surprised at my findings when I did go up a couple of weeks ago. The ceiling was totalky drenched with water droplets (condensation), there was damp on the floor, insulation and rafters. A couple of rafters were showing signs of mold growth, everything felt damp and some boxes actually had puddles of water on them (no exaggeration). Immediately did some research and ordered these items. Cleaned out mold fully, tidied up loft and installed these about two weeks ago, and despite having lots of reservations, these things worked a treat. Loft is now completely free from any condensation ... even signs of the mold had disappeared, so genuinely surprised and could not believe it. Installation was very simple. The loft is now obviously colder due to the outside air coming in, but better this than condensation. Early days but time will tell if it does deliver long term. Main downside is price which seems very expensive for what is essentially very basic flimsy PVC. I guess you're paying for the design, ease of use and primarily the niche product/market.
Review: Fantastic! We recently moved into our first own home - Fantastic! We recently moved into our first own home, an early 1970's semi-detached house with practically no loft insulation. I fitted a 12 inches deep layer of insulation to the loft and it certainly helped the warmth in the house but on the first venture into the loft on a frosty day I found the whole place was like it was raining indoors with condensation dripping off the inside of the roof felt, especially bad on the colder front of the house which gets less sun. With mounting repair bills for the old house we were really worried about how we could fix the problem as everything in the loft was soaked and damp was destroying anything we had stored up there. Searching for a solution I learned about these felt lap vents from a roof repair specialist who post videos on youtube and advised these may be a good DIY fix. A quick search on desertcart and I was delighted to find some for sale so I bought a pack of 20 in the hope they would help the problem. The vents are very easy to fit and I installed 10 per side, 5 low and 5 high, staggering the vents so no two are in line. Anywhere the felt was a bit stuck I used an old butter knife to gently free it up so the vent could slide in. Immediately you can feel a slight air current entering through the vent and with all 20 vents fitted I towel dried as much of the damp belongings as I could and left it be for a couple of days. Upon checking the loft again a couple of days later I found the loft was dry, no condensation and the damp musty air was gone. The vents have been in place for a few weeks now through frost, snow and heavy rain and our loft is dry and our belongings have been saved. We were so worried about possible high repair bills and now are delighted the problem has been solved so easily and cheaply. I would highly recommend these vents for anyone suffering from a damp attic caused by condensation.

## Features

- The Manthorpe G630 Felt Lap Ventilator is a refurbishment product that is designed to increase the amount of ventilation into existing roof spaces with a lapped felt/ membrane construction.
- The product is intended to be fitted retrospectively to properties that have had additional loft insulation recently installed. The vent will help to combat the problem of condensation build up caused by the extra insulation by adding additional ventilation into the roof space.
- The product will not meet the requirement for roof space ventilation solely on its own it will only provide airflow through the felt laps into the batten void.
- The product has been designed as a remedial solution to help overcome the build-up of condensation in the roof space, however like all products that open the felt lap to provide ventilation it does not meet the code of practice BS 5534:2014+A2:2018 6.2.1.1
- The specifier or user should be aware that the opening of felt laps on the roof may adversely affect the driving rain resistance of the slates, tiles or shingles, as well as increase the wind uplift forces acting on them.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| Manufacturer | Manthorpe |
| Part Number | G630 |
| Package Dimensions | 30.1 x 23.4 x 12.3 cm; 1.63 kg |
| Manufacturer reference | G630 |
| Item Package Quantity | 20 |
| Batteries included? | No |
| Batteries Required? | No |
| Item Weight | 1.63 kg |

## Images

![Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow - Image 1](https://m.media-amazon.com/images/I/71Ax5y1ZuZL.jpg)
![Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow - Image 2](https://m.media-amazon.com/images/I/41WXCfJYr2L.jpg)
![Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow - Image 3](https://m.media-amazon.com/images/I/415q68i8WEL.jpg)
![Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow - Image 4](https://m.media-amazon.com/images/I/81Od9IuMTEL.jpg)
![Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow - Image 5](https://m.media-amazon.com/images/I/9171s5Zpl3L.jpg)

## Questions & Answers

**Q: Would these help the loft space to not get hot in 30degree heat**
A: If you don't already have ventilation grills in your tiles or soffit, they will help equalise but only to outside air temperature.
I used them to remove moisture and damp caused from a bathroom below and poor ventilation. 
They probably work better in old roofs like mine as the tiles don't interlock tightly.

**Q: My attic has the breathable membrane ,not felt, still get condensation will these vents fit on**
A: Thought they were brilliant. They should fit between the rafters. Clips onto the lower membrane, where they overlap. It pushes the membranes apart so there is a gap between them, so lets the cold air in and warm air out. My biggest problem was how many to fit. Ended up staggering them evenly between overlaps and rafters.

**Q: The rafters in our roof are only 300mm apart can you cut these down to fit?**
A: It is a few years since I fitted these. But looking at the picture to refresh my memory I can't see or think of any reason why not .

**Q: The package dimensions state 30.23cm. Assume this is the width of the vent, i.e. ~ 30cm?**
A: The dimensions given in the description are the shipped package dimensions. ie: the size of the box they are delivered in. Individual physical size is  11.5 inches x 8 inches approx.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Absolutely Excellent (so far), but expensive.
*by M***8 on 13 February 2021*

Hadn't been in the loft for a couple of months so was really surprised at my findings when I did go up a couple of weeks ago. The ceiling was totalky drenched with water droplets (condensation), there was damp on the floor, insulation and rafters. A couple of rafters were showing signs of mold growth, everything felt damp and some boxes actually had puddles of water on them (no exaggeration). Immediately did some research and ordered these items. Cleaned out mold fully, tidied up loft and installed these about two weeks ago, and despite having lots of reservations, these things worked a treat. Loft is now completely free from any condensation ... even signs of the mold had disappeared, so genuinely surprised and could not believe it. Installation was very simple. The loft is now obviously colder due to the outside air coming in, but better this than condensation. Early days but time will tell if it does deliver long term. Main downside is price which seems very expensive for what is essentially very basic flimsy PVC. I guess you're paying for the design, ease of use and primarily the niche product/market.

### ⭐⭐⭐⭐⭐ Fantastic! We recently moved into our first own home
*by B***D on 7 February 2018*

Fantastic! We recently moved into our first own home, an early 1970's semi-detached house with practically no loft insulation. I fitted a 12 inches deep layer of insulation to the loft and it certainly helped the warmth in the house but on the first venture into the loft on a frosty day I found the whole place was like it was raining indoors with condensation dripping off the inside of the roof felt, especially bad on the colder front of the house which gets less sun. With mounting repair bills for the old house we were really worried about how we could fix the problem as everything in the loft was soaked and damp was destroying anything we had stored up there. Searching for a solution I learned about these felt lap vents from a roof repair specialist who post videos on youtube and advised these may be a good DIY fix. A quick search on Amazon and I was delighted to find some for sale so I bought a pack of 20 in the hope they would help the problem. The vents are very easy to fit and I installed 10 per side, 5 low and 5 high, staggering the vents so no two are in line. Anywhere the felt was a bit stuck I used an old butter knife to gently free it up so the vent could slide in. Immediately you can feel a slight air current entering through the vent and with all 20 vents fitted I towel dried as much of the damp belongings as I could and left it be for a couple of days. Upon checking the loft again a couple of days later I found the loft was dry, no condensation and the damp musty air was gone. The vents have been in place for a few weeks now through frost, snow and heavy rain and our loft is dry and our belongings have been saved. We were so worried about possible high repair bills and now are delighted the problem has been solved so easily and cheaply. I would highly recommend these vents for anyone suffering from a damp attic caused by condensation.

### ⭐⭐⭐⭐ Seems to do the job!
*by W***L on 13 March 2019*

We live in a 4 bed detached house and suddenly started having trouble with condensation in the loft - it was pretty bad with drips coming off the felt. Rather than mucking about with getting soffit vents fitted I thought I’d give these a whirl. I read other reviews that said that you’d probably need more than 10 so I thought I’d start with 20 and see how it went. I tried shoving them in randomly between the overlaps in the roofing felt and often found that either tiles or wood batons were obstructing the vent from being fitted. The result was that the placement wasn’t quite as random as I’d have hoped (which is said to improve air flow). However, the end result is good. We don’t seem to have any evidence of condensation any more! That said, it has been a bit warmer these last few weeks so only time will tell. A little expensive for what they are (considering they’re just injection moulded plastic) and one of them broke a little during insertion. Others have said that sticking some halved pipe insulation between the felt would work just as well but these were convenient and pretty easy to install - aside from the issues I had with the exact structure of my roof.

## Frequently Bought Together

- Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow
- 10 x Felt Lap Vents Prevents Loft roof Condensation. Attic Space Ventilation
- 10 x Manthorpe Felt Lap Vent, Roof Loft Ventilation, Cures Loft Condensation

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*Product available on Desertcart Singapore*
*Store origin: SG*
*Last updated: 2026-10-06*